Articles on Medical Diseases and Conditions

Month: December 2009

  • Female Delayed Puberty and Primary Amenorrhea

    Onset of normal puberty in girls is somewhat variable, with disagreement in the literature concerning at what age to diagnose precocious puberty and at what age to suspect delayed puberty. The most generally agreed-on range of onset for female puberty is between 9 and 16 years. Signs of puberty include breast development, growth of pubic and axillary hair, and estrogen effect as seen in vaginal smears using the Papanicolaou stain. Menstruation also begins; if it does not, the possibility of primary amenorrhea arises. Primary amenorrhea may or may not be accompanied by evidence that suggests onset of puberty, depending on the etiology of the amenorrhea. Some of the causes of primary amenorrhea are listed in the box.

    Some Etiologies of Female Delayed Puberty and Primary Amenorrhea
    Mullerian dysgenesis (Mayer-Rokitansky syndrome): congenital absence of portions of the female genital tract, with absent or hypoplastic vagina. Ovarian function is usually normal. Female genotype and phenotype.
    Male pseudohermaphroditism: genetic male (XY karotype) with female appearance due to deficiency of testosterone effect.
    1. Testicular feminization syndrome: lack of testosterone effect due to defect in tissue testosterone receptors.
    2. Congenital adrenal hyperplasia: defect in testosterone production pathway.
    3. Male gonadal dysgenesis syndromes: defect in testis function.
    a. Swyer syndrome (male pure gonadal dysgenesis): female organs present except for ovaries. Bilateral undifferentiated streak gonads. Presumably testes never functioned and did not prevent mьllerian duct development.
    b. Vanishing testes syndrome (XY gonadal agenesis): phenotype varies from male pseudohermaphrodite to ambiguous genitalia. No testes present. Presumably testes functioned in very early embryologic life, sufficient to prevent mьllerian duct development, and then disappeared.
    c. Congenital anorchia: male phenotype, but no testes. Presumably, testes functioned until male differentiation took place, then disappeared.
    Female sex chromosome abnormalities (Turner’s syndrome—female gonadal dysgenesis— and Turner variants): XO karyotype in 75%-80% of patients, mosaic in others. Female phenotype. Short stature in most, web neck in 40%. Bilateral streak gonads.
    Polycystic (Stein-Leventhal) or nonpolycystic ovaries, not responsive to gonadotropins.
    Deficient gonadotropins due to hypothalamic or pituitary dysfunction.
    Hyperprolactinemia: pituitary overproduction of prolactin alone.
    Effects of severe chronic systemic disease: chronic renal disease, severe chronic GI disease, anorexia nervosa, etc.
    Constitutional (idiopathic) delayed puberty: puberty eventually takes place, so this is a retrospective diagnosis.
    Other: Cushing’s syndrome, hypothyroidism, and isolated GH deficiency can result in delayed puberty.

    Physical examination is very important to detect inguinal hernia or masses that might suggest the testicular feminization type of male pseudohermaphroditism, to document the appearance of the genitalia, to see the pattern of secondary sex characteristics, and to note what evidence of puberty exists and to what extent. Pelvic examination is needed to ascertain if there are anatomical defects preventing menstruation, such as a nonpatent vagina, and to detect ovarian masses.

    Laboratory tests

    Basic laboratory tests begin with chromosome analysis, since a substantial minority of cases have a genetic component. Male genetic sex indicates male pseudohermaphroditism and leads to tests that differentiate the various etiologies. Turner’s syndrome and other sex chromosome disorders are also excluded or confirmed. If there is a normal female karyotype and no chromosome abnormalities are found, there is some divergence of opinion on how to evaluate the other important organs of puberty—the ovaries, pituitary, and hypothalamus. Some prefer to perform serum hormone assays as a group, including pituitary gonadotropins (FSH and LH), estrogen (estradiol), testosterone, prolactin, and thyroxine. Others perform these assays in a step-by-step fashion or algorithm, depending on the result of each test, which could be less expensive but could take much more time. Others begin with tests of organ function. In the algorithm approach, the first step is usually to determine if estrogen is present in adequate amount. Vaginal smears, serum estradiol level, endometrial stimulation with progesterone (for withdrawal bleeding), and possibly endometrial biopsy (for active proliferative or secretory endometrium, although biopsy is considered more often in secondary than in primary amenorrhea)—all are methods to detect ovarian estrogen production. If estrogen is present in adequate amount, this could mean intact hypothalamic-pituitary-ovarian feedback or could raise the question of excess androgen (congenital adrenal hyperplasia, Cushing’s syndrome, PCO disease, androgen-producing tumor) or excess estrogens (obesity, estrogen-producing tumor, iatrogenic, self-medication). If estrogen effect is absent or very low, some gynecologists then test the uterus with estrogen, followed by progesterone, to see if the uterus is capable of function. If no withdrawal bleeding occurs, this suggests testicular feminization, congenital absence or abnormality of the uterus, or the syndrome of intrauterine adhesions (Asherman’s syndrome). If uterine withdrawal bleeding takes place, the uterus can function, and when this finding is coupled with evidence of low estrogen levels, the tentative diagnosis is ovarian failure.

    The next step is to differentiate primary ovarian failure from secondary failure caused by pituitary or hypothalamic disease. Hypothalamic dysfunction may be due to space-occupying lesions (tumor or granulomatous disease), infection, or (through uncertain mechanism) effects of severe systemic illness, severe malnutrition, and severe psychogenic disorder. X-ray films of the pituitary are often ordered to detect enlargement of the sella turcica from pituitary tumor or suprasellar calcifications due to craniopharyngioma. Polytomography is more sensitive for sellar abnormality than ordinary plain films. CT also has its advocates. Serum prolactin, thyroxine, FSH, and LH assays are done. It is necessary to wait 4-6 weeks after a progesterone or estrogen-progesterone test before the hormone assays are obtained to allow patient hormone secretion patterns to resume their pretest status. An elevated serum prolactin value raises the question of pituitary tumor (especially if the sella is enlarged) or idiopathic isolated hyperprolactinemia. However, patients with the empty sella syndrome and some patients with hypothyroidism may have an enlarged sella and elevated serum prolactin levels, and the other causes of elevated prolactin levels (see the box) must be considered. A decreased serum FSH or LH level confirms pituitary insufficiency or hypothalamic dysfunction. A pituitary stimulation test can be performed. If the pituitary can produce adequate amounts of LH, this suggests hypothalamic disease (either destructive lesion, effect of severe systemic illness, or malnutrition). However, failure of the pituitary to respond does not necessarily indicate primary pituitary disease, since severe long-term hypothalamic deficiency may result in temporary pituitary nonresponsiveness to a single episode of test stimulation. Hormone therapy within the preceding 4-6 weeks can also adversely affect test results.

    The box lists some conditions associated with primary amenorrhea or delayed puberty and the differential diagnosis associated with various patterns of pituitary gonadotropin values. However, several cautionary statements must be made about these patterns. Clearly elevated FSH or LH values are much more significant than normal or mildly to moderately decreased levels. Current gonadotropin immunoassays are technically more reproducible and dependable at the upper end of usual values than at the lower end. Thus, two determinations on the same specimen could produce both a mildly decreased value and a value within the lower half of the reference range. In addition, blood levels of gonadotropins, especially LH, frequently vary throughout the day. The values must be compared with age- and sexmatched reference ranges. In girls, the levels also are influenced by the menstrual cycle, if menarche has begun. Second, the conditions listed—even the genetic ones, although to a lesser extent—are not homogeneous in regard to severity, clinical manifestations, or laboratory findings. Instead, each represents a spectrum of patients. The more classic and severe the clinical manifestations, the more likely that the patient will have “expected” laboratory findings, but even this rule is not invariable. Therefore, some patients having a condition typically associated with an abnormal laboratory test result may not show the expected abnormality. Laboratory error is another consideration. Also, the spectrum of patients represented by each condition makes it difficult to evaluate reports of laboratory findings due to differences in patient population, severity of illness, differences in applying diagnostic criteria to the patients, variance in specimen collection protocols, and technical differences in the assays used in different laboratories. In many cases, adequate data concerning frequency that some laboratory tests are abnormal are not available.

    Gonadotropin Levels in Certain Conditions Associated With Primary Amenorrhea or Delayed Puberty
    FSH and LH decreased*
    Hypopituitarism
    Hypothalamic dysfunction
    Constitutional delayed puberty
    Some cases of primary hypothyroidism
    Some cases of Cushing’s syndrome
    Some cases of severe chronic illness
    FSH and LH increased†
    Some cases of congenital adrenal hyperplasia
    Female gonadal dysgenesis
    Male gonadal dysgenesis
    Ovarian failure due to nonovarian agents
    LH increased, FSH not increased‡
    Testicular feminization
    Some cases of PCO disease

    Elevated FSH and LH levels or an elevated LH level alone suggests primary ovarian failure, whether from congenital absence of the ovaries or congenital inability to respond to gonadotropins, acquired abnormality such as damage to the ovaries after birth, or PCO disease.

    An elevated estrogen or androgen level raises the question of hormone-secreting tumor, for which the ovary is the most common (but not the only) location. Nontumor androgen production may occur in PCO disease and Cushing’s syndrome (especially adrenal carcinoma).

    As noted previously, there is no universally accepted single standard method to investigate female reproductive disorders. Tests or test sequences vary among medical centers and also according to findings in the individual patients.

    When specimens for pituitary hormone assays are collected, the potential problems noted earlier in the chapter should be considered.

  • Precocious Puberty

    Precocious puberty can be isosexual (secondary sex characteristics of the same sex) or heterosexual (masculinization in girls and feminization in boys). The syndromes have been further subdivided into those that produce true puberty with functioning gonads and those that produce pseudopuberty, in which development of secondary sex characteristics suggests puberty but the gonads do not function. The major causes of precocious puberty are idiopathic early puberty or the hyper secretion of androgens or estrogens from hypothalamic, pituitary, adrenal, gonadal, or factitious (self-medication) sources.

    Hypothalamic precocious puberty is usually associated with a tumor (e.g., a pinealoma) involving the hypothalamus or with encephalitis. The result is always an isosexual true puberty.

    Pituitary precocious puberty is usually idiopathic (“constitutional”). The result is normal isosexual puberty. In girls the condition rarely may be due to Albright’s syndrome (polyostotic fibrous dysplasia). Primary pituitary tumors do not cause precocious puberty.

    Gonadal precocious puberty in boys results from a Leydig cell tumor of the testis that produces testosterone. This is a pseudopuberty, since FSH is not produced and no spermatogenesis occurs. In girls, various ovarian tumors may cause pseudopuberty, which may be either isosexual or heterosexual, depending on whether the tumor secretes estrogens or androgens. Granulosa-theca cell tumors are the most frequent, although their peak incidence is not until middle age. These tumors most frequently produce estrogens. Dysgerminoma and malignant teratoma are two uncommon ovarian tumors that may produce hCG rather than the usual type of estrogens.

    Adrenal precocious puberty is due to either congenital adrenal hyperplasia or adrenal tumor. In early childhood, congenital adrenal hyperplasia is more likely; if onset is in late childhood or prepubertal age, tumor is more likely. In both cases a pseudopuberty results, usually isosexual in boys and heterosexual (virilization) in girls. Congenital adrenal hyperplasia may also produce pseudohermaphroditism (simulation of male genitalia) in infant girls.

    Hypothyroidism has been reported to cause rare cases of true isosexual precocious puberty in both boys and girls.

    Laboratory evaluation

    Laboratory evaluation depends on whether the physical examination indicates isosexual or heterosexual changes. In girls, heterosexual changes point toward congenital adrenal hyperplasia, ovarian tumor, or adrenal carcinoma. The most important test for diagnosis of congenital adrenal hyperplasia is plasma 17-hydroxyprogesterone (17-OH-P) assay. A 24-hour urine specimen for 17-ketosteroids (17-KS) is also very helpful, since the 17-KS values are elevated in 80%-85% adrenal carcinoma, frequently elevated in congenital adrenal hyperplasia, and sometimes elevated in ovarian carcinoma. If test results for congenital adrenal hyperplasia are negative, normal urine 17-KS levels point toward ovarian tumor. Ultrasound examination of the ovaries and adrenals and an overnight dexamethasone screening test for adrenal tumor are helpful. Computerized tomography (CT) of the adrenals is also possible, but some believe that CT is less successful in childhood than in adults. Isosexual changes suggest hypothalamic area tumor, constitutional precocious puberty, ovarian estrogen-secreting tumor, or hypothyroidism. Useful tests include serum thyroxine assay, ultrasound examination of the ovaries, and CT scan of the hypothalamus area. The possibility of exposure to estrogen-containing creams or other substances should also be investigated. Serum hCG levels may be elevated in the rare ovarian choriocarcinomas.

    Female isosexual precocious puberty must be distinguished from isolated premature development of breasts (thelarche) or pubic hair (adrenarche). Female heterosexual precocious puberty must be distinguished from hirsutism, although this is a more common problem during and after puberty.

    In boys, heterosexual precocious pseudopuberty suggests estrogen-producing tumor (testis choriocarcinoma or liver hepatoblastoma) or the pseudohermaphrodite forms of congenital adrenal hyperplasia. Tests for congenital adrenal hyperplasia plus serum hCG are necessary. Isosexual precocious puberty could be due to a hypothalamic area tumor, constitutional (idiopathic) cause, testis tumor (Leydig cell type), hypothyroidism, or congenital adrenal hyperplasia. Necessary tests include those for congenital adrenal hyperplasia and a serum thyroxine determination. If the results are negative, serum testosterone (to detect values elevated above normal puberty levels) and hypothalamic area CT scan are useful. Careful examination of the testes for tumor is necessary in all cases of male precocious puberty.

  • Male Infertility or Hypogonadism

    About 40%-50% of infertility problems are said to be due to dysfunction of the male reproductive system. Male infertility can be due to hormonal etiology (either lack of gonadotropin or suppression of spermatogenesis), nonhormonal factors affecting spermatogenesis, primary testicular disease, obstruction to sperm passages, disorders of sperm motility or viability or presence of antisperm antibodies (see the box on this page). About 30%-40% is reported to be associated with varicocele. Diagnosis and investigation of etiology usually begins with physical examination (with special attention to the normality of the genitalia and the presence of a varicocele), semen analysis (ejaculate quantity, number of sperm, sperm morphology, and sperm motility), and serum hormone assay (testosterone, LH, and FSH).

    Some Important Causes of Male Infertility, Classified According to Primary Site of the Defect

    Hormonal
    Insufficient hypothalamic gonadotropin (hypogonadotropic eunuchoidism)
    Insufficient pituitary gonadotropins (isolated LH deficiency [“fertile eunuch”] or pituitary
    insufficiency)
    Prolactin-secreting pituitary adenoma
    Excess estrogens (cirrhosis, estrogen therapy, estrogen-producing tumor)
    Excess androgens
    Excess glucocorticosteroids
    Hypothyroidism
    Nonhormonal factors affecting testis sperm production
    Varicocele
    Poor nutrition
    Diabetes mellitus
    Excess heat in area of testes
    Stress and emotion
    Drugs and chemicals
    Febrile illnesses
    Cryptochism(undescended testis, unilateral or bilateral)
    Spinal cord injuries
    Primary testicular abnormality
    Maturation arrest at germ cell stage
    “Sertoli cell only” syndrome
    Klinefelter’s syndrome and other congenital sex chromosome disorders
    Testicular damage (radiation, mumps orchitis, inflammation, trauma)
    Myotonic dystrophy
    Posttesticular abnormality
    Obstruction of sperm passages
    Impaired sperm motility
    Antisperm antibodies

    Testicular function tests. Male testicular function is based on formation of sperm by testicular seminiferous tubules under the influence of testosterone. FSH is necessary for testicular function because it stimulates seminiferous tubule (Sertoli cell) development. Testosterone secretion by the Leydig cells (interstitial cells) of the testis is necessary for spermatogenesis in seminiferous tubules capable of producing sperm. LH (in males sometimes called “interstitial cell-stimulating hormone”) stimulates the Leydig cells to produce testosterone. Testosterone is controlled by a feedback mechanism whereby testosterone levels regulate hypothalamic secretion of GnRH, which, in turn, regulates pituitary secretion of LH. The adrenals also produce androgens, but normally this is not a significant factor in males. In classic cases, serum levels of testosterone and gonadotropins (LH and FSH) can differentiate between primary testicular abnormality (failure of the testis to respond to pituitary gonadotropin stimulation, either congenital or acquired) and pituitary or hypothalamic dysfunction (either congenital or acquired). In primary gonadal (testis) insufficiency, pituitary gonadotropin levels are usually elevated. Of the various categories of primary gonadal insufficiency, the Klinefelter’s xxy chromosome syndrome in its classic form shows normal FSH and LH gonadotropin levels during childhood, but after puberty both FSH and LH levels are elevated and the serum testosterone level is low. Klinefelter’s syndrome exists in several variants, however, and in some cases LH levels may be within reference range (single LH samples also may be confusing because of the pulsatile nature of LH secretion). Occasionally patients with Klinefelter’s syndrome have low-normal total serum testosterone levels (due to an increase in SHBG levels) but decreased free testosterone levels. Elevated pituitary gonadotropin levels should be further investigated by a buccal smear for sex chromatin to elevate the possibility of Klinefelter’s syndrome. Some investigators may perform a chromosome analysis because of possible inaccuracies in buccal smear interpretation and because some persons with Klinefelter’s syndrome have cell mosaicism rather than the same chromosome pattern in all cells, or a person with findings suggestive of Klinefelter’s syndrome may have a different abnormal chromosome karyotype. In the “Sertoli cell only syndrome,” testicular tubules are abnormal but Leydig cells are normal. Therefore, the serum FSH level is elevated but LH and testosterone levels are usually normal. In acquired gonadal failure (due to destruction of the testicular tubules by infection, radiation, or other agents), the FSH level is often (but not always) elevated, whereas LH and testosterone levels are often normal (unless the degree of testis destruction is sufficient to destroy most of the Leydig cells, a very severe change). In secondary (pituitary or hypothalamic) deficiency, both the pituitary gonadotropin (FSH and LH) and the testosterone levels are low.

    Although serum testosterone is normally an indicator of testicular Leydig cell function and, indirectly, of pituitary LH secretion, other factors can influence serum testosterone levels. The adrenal provides much of the precursor steroids for testosterone, and some types of congenital adrenal hyperplasia result in decreased levels of testosterone precursors. Cirrhosis may decrease serum testosterone levels. Increase or decrease of testosterone-binding protein levels may falsely increase or decrease serum testosterone levels, since the total serum testosterone value is being measured, whereas assay of free (unbound) testosterone is not affected.

    Stimulation tests. Stimulation tests are available to help determine which organ is malfunctioning in equivocal cases.

    1. HCG directly stimulates the testis, increasing testosterone secretion to at least twice baseline values.
    2. Clomiphene stimulates the hypothalamus, producing increases in both LH and testosterone levels. The medication is given for 10 days. However, clomiphene does not stimulate LH production significantly in prepubertal children. Serum testosterone and LH values must be close to normal pubertal or adult levels before the test can be performed, and the test can be used only when there is a mild degree of abnormality in the gonadal-pituitary system.
    3. The GnRH stimulation test can directly evaluate pituitary capability to produce LH and FSH and can indirectly evaluate testicular hormone-producing function that would otherwise depend on measurement of basal testosterone levels. Normally, pituitary LH stimulates testosterone production from Leydig cells of the testis, and the amount of testosterone produced influences hypothalamic production of GnRH, which controls pituitary LH. When exogenous (test) GnRH is administered, the pituitary is stimulated to produce LH. The release of testosterone from the testis in response to LH stimulation inhibits further LH stimulation to some degree. In most male patients with primary gonadal failure, basal serum LH and FSH become elevated due to lack of inhibitory feedback from the testis. However, some patients may have basal serum LH and FSH levels in the lower part of the population reference range, levels that are indistinguishable from those of some normal persons; although preillness values were higher in these patients, their preillness normal levels are rarely known. In these patients, a GnRH stimulation test may be useful. Some investigators have found that the degree of inhibition of LH production in response to GnRH administration is more sensitive in detecting smaller degrees of testicular hormone production insufficiency than basal LH levels. The decreased testosterone levels decrease feedback inhibition on the hypothalamus and administration of GnRH results in an exaggerated LH or FSH response (markedly elevated LH and FSH levels compared to levels in normal control persons). The test is performed by obtaining a baseline serum specimen for LH and FSH followed by an intravenous (IV) bolus injection of 100 µg of synthetic GnRH. Another serum specimen is obtained 30 minutes later for LH and FSH. Certain factors can influence or interfere with GnRH results. Estrogen administration increases GnRH effect by sensitizing the pituitary, and androgens decrease the effect. Patient sex and age (until adult pulsatile secretion schedule is established) also influence test results. When used as a test for pituitary function, some patients with clinically significant degrees of failure show a normal test result; therefore, only an abnormal result is definitely significant.

    Semen analysis. Semen analysis is an essential part of male infertility investigation. Semen findings that are highly correlated with hypofertility or infertility include greatly increased or decreased ejaculate volume, very low sperm counts, greatly decreased sperm motility, and more than 20% of the sperm showing abnormal morphology. However, the World Health Organization (WHO) recently changed its definition of semen morphologic abnormality, and now considers a specimen abnormal if more than 70% of the sperm have abnormal morphology. One particular combination of findings is known as the “stress pattern” and consists of low sperm count, decreased sperm motility, and more than 20% of the sperm being abnormal in appearance (especially with an increased number of tapering head forms instead of the normal oval head). The stress pattern is suggestive of varicocele but can be due to acute febrile illness (with effects lasting up to 60 days), some endocrine abnormalities, and antisperm agents. An abnormal semen analysis should be repeated at least once after 3 weeks and possibly even a third time, due to the large variation within the population and variation of sperm production even within the same person as well as the temporary effects of acute illness. Most investigators recommend that the specimen be obtained 2-3 days after regular intercourse to avoid artifacts that may be produced by prolonged sperm storage. The specimen should be received by the laboratory by 1 hour after it is obtained, during which time it should be kept at room temperature.

    Semen analysis: sperm morphology

    Fig. 31-1 Semen analysis: sperm morphology. a, acrosome; b, nucleus (difficult to see); c, post-acrosomal cap; d, neckpiece; e, midpiece (short segment after neckpiece); f, tail. A, normal; B, normal (slightly different head shape); C, tapered head; D, tapered head with acrosome deficiency; E, acrosomal deficiency; F, head vacuole; G, cytoplasmic extrusion mass; H, bent head (bend of 45° or more); I, coiled tail; J, coiled tail; K, double tail; L, pairing phenomenon (sperm agglutination); M, sperm precursors (spermatids); N, bicephalic sperm.

    Testicular biopsy. Testicular biopsy may be useful in a minority of selected patients in whom no endocrinologic or other cause is found to explain infertility. Most investigators agree that complete lack of sperm in semen analysis is a major indication for biopsy but disagree on whether biopsy should be done if sperm are present in small numbers. Biopsy helps to differentiate lack of sperm production from sperm passage obstruction and can suggest certain possible etiologies of testicular dysfunction or possible areas to investigate. However, none of the histopathologic findings is specific for any one disease. The report usually indicates if spermatogenesis is seen and, if so, whether it is adequate, whether there are normal numbers of germ cells, and whether active inflammation or extensive scarring is present.

    Serum antisperm antibody studies. In patients with no evidence of endocrine, semen, or other abnormality, serum antisperm antibody titers can be measured. These studies are difficult to perform and usually must be done at a center that specializes in reproductive studies or therapy. Serum antisperm antibodies are a common finding after vasectomy, being reported in about 50% of cases (literature range, 30%-70%). The incidence and significance of serum antisperm antibodies in couples with infertility problems are somewhat controversial. There is wide variance of reported incidence (3.3%-79%), probably due to different patient groups tested and different testing methods. In men, one report suggests that serum antibody titer is more significant than the mere detection of antibody. High titers of antisperm antibody in men were considered strong evidence against fertility; low titers were of uncertain significance, and mildly elevated titers indicated a poor but not hopeless prognosis. In women, serum antisperm antibodies are said to be present in 7%-17% of infertility cases but their significance is rather uncertain, since a considerable percentage of these women can become pregnant. Antisperm antibody detected in the cervical mucus of women is thought to be much more important than that detected in serum. A test showing ability of sperm to bind to mannose may be available.

  • Tests of Gonadal Function

    The most common conditions in which gonadal function tests are used are hypogonadism in males and menstrual disorders, fertility problems, and hirsutism or virilization in females. The hormones currently available for assistance include lutropin (luteinizing hormone; LH), follitropin (follicle-stimulating hormone; FSH), testosterone, human chorionic gonadotropin (hCG), and gonadotropin-releasing hormone (GnRH).

    Gonadal function is regulated by hypothalamic secretion of a peptide hormone known as gonadotropin-releasing hormone (GnRH; also called luteinizing hormone-releasing hormone, LHRH). Secretion normally is in discontinuous bursts or pulses, occurring about every 1.5-2.0 hours (range, 0.7-2.5 hours). GnRH half-life normally is about 2-4 minutes (range, 2-8 minutes). There is little if any secretion until the onset of puberty (beginning at age 8-13 years in females and age 9-14 years in males). Then secretion begins predominately at night but later extends throughout the night into daytime, until by late puberty secretion takes place all 24 hours. GnRH is secreted directly into the circulatory channels between the hypothalamus and pituitary. GnRH causes the basophilic cells of the pituitary to secrete LH and FSH. In males LH acts on Leydig cells of the testis to produce testosterone, whereas FSH stimulates Sertoli cells of the testis seminiferous tubules into spermatogenesis, assisted by testosterone. In females, LH acts on ovarian thecal cells to produce testosterone, whereas FSH stimulates ovarian follicle growth and also causes follicular cells to convert testosterone to estrogen (estradiol). There is a feedback mechanism from target organs to the hypothalamus to control GnRH secretion. In males, testosterone and estradiol inhibit LH secretion at the level of the hypothalamus, and testosterone also inhibits LH production at the level of the pituitary. A hormone called inhibitin, produced by the Sertoli cells of the testis tubules, selectively inhibits FSH at both the hypothalamic and pituitary levels. There appears to be some inhibitory action of testosterone and estradiol on FSH production as well, in some circumstances. In females, there is some inhibitory feedback to the hypothalamus by estradiol.

    Luteinizing hormone and follicle-stimulating hormone

    Originally FSH and LH were measured together using bioassay methods, and so-called FSH measurements included LH. Immunoassay methods can separate the two hormones. The LH cross-reacts with hCG in some RIA systems. Although this ordinarily does not create a problem, there is difficulty in pregnancy and in patients with certain neoplasms that secrete hCG. Several of the pituitary and placental glycopeptides (TSH, FSH, hCG, LH) are composed of at least two immunologic units, alpha and beta. All of these hormones have the same immunologic response to their alpha fraction but a different response to each beta subunit. Antisera against the beta subunit of hCG eliminate interference by LH, and some investigators have reported success in producing antisera against the beta subunit of LH, which does not detect hCG. There is some cross-reaction between FSH and TSH, but as yet this has not seemed important enough clinically in TSH assay to necessitate substitution of TSH beta subunit antiserum for antisera already available. Assay of FSH in serum is thought to be more reliable than in urine due to characteristics of the antibody preparations available.

    Serum luteinizing hormone

    LH is secreted following intermittent stimulation by GnRH in pulses occurring at a rate of about 2-4 every 6 hours, ranging from 30% to nearly 300% over lowest values. Therefore, single isolated LH blood levels may be difficult to interpret and could be misleading. It has been suggested that multiple samples be obtained (e.g., four specimens, each specimen collected at a 20-minute interval from another). The serum specimens can be pooled to obtain an average value. FSH and testosterone have a relatively constant blood level in females.

    Urine luteinizing hormone

    In contrast to serum LH, urine LH is more difficult to obtain, since it requires a 24-hour specimen with the usual problem of complete specimen collection. It also has the disadvantage of artifact due to urine concentration or dilution. The major advantage is averaging of 24-hour secretion, which may prevent misleading results associated with serum assays due to LH pulsatile secretion. Another role for urine LH assay is detection of ovulation during infertility workups. LH is rapidly excreted from plasma into urine, so that a serum LH surge of sufficient magnitude is mirrored in single urine samples. An LH surge precedes ovulation by about 24-36 hours (range, 22-4 hours). Since daily urine specimens are obtained beginning 9-10 days after onset of menstruation (so as not to miss the LH surge preceding ovulation if ovulation should occur earlier than the middle of the patient cycle). It has been reported that the best time to obtain the urine specimen is during midday (11 A.M.-3 P.M.) because the LH surge in serum usually takes place in the morning (5 A.M.-9 A.M.). In one study, the LH surge was detected in 56% of morning urine specimens, 94% of midday specimens, and 88% of evening specimens. In contrast, basal body temperature, another method of predicting time of ovulation, is said to be accurate in only 40%-50% of cases. Several manufacturers have marketed simple immunologic tests for urine LH with a color change endpoint that can be used by many patients to test their own specimens. Possible problems include interference by hCG with some of the LH kits, so that early pregnancy could simulate a LH surge. Since the LH surge usually does not last more than 2 days, positive test results for more than 3 consecutive days suggest some interfering factor. Similar interference may appear in some patients with elevated serum LH levels due to ovarian failure (polycystic ovary [PCO] disease, early menopause, etc.).

    Finally, an estimated 10% of patients have more than one urine LH spike, although the LH surge has the greatest magnitude. It may be necessary to obtain serum progesterone or urine pregnanediol glucuronide assays to confirm that elevation of LH values is actually the preovulation LH surge.

    Urine pregnanediol

    The ovarian corpus luteum formed shortly after ovulation secretes increasing amounts of progesterone. Progesterone or its metabolite pregnanediol glucuronide begins to appear in detectable quantities about 2-3 days after ovulation (3-5 days after the LH surge) and persists until about the middle of the luteal phase that ends in menstruation. Conception is followed by progesterone secretion by the placenta. A negative baseline urine pregnanediol assay before the LH surge followed by a positive pregnanediol test result on at least 1 day of early morning urine specimens obtained 7, 8, and 9 days after the LH surge confirm that the LH surge did occur and was followed by ovulation and corpus luteum formation. Urine specimens are collected in the morning rather than at the LH collection time of midday. At least one manufacturer markets a simple kit for urine pregnanediol assay.

    Problems with interpretation of a positive urine pregnanediol glucuronide assay include the possibility that early pregnancy may be present. Also, 5%-10% of patients throughout their menstrual cycle nonovulatory phase have slightly or mildly increased pregnanediol levels compared to the reference range. A urine sample collected before the LH surge can be tested to exclude or demonstrate this phenomenon.

    Serum androgens

    The most important androgens are dehydroepiandrosterone (DHEA), a metabolite of DHEA called DHEA-sulfate (DHEA-S), androstenedione, and testosterone. DHEA is produced in the adrenal cortex, ovary, and testis (in the adrenal cortex, the precursors of DHEA are also precursors of cortisol and aldosterone, which is not the case in the ovary or testis). DHEA is the precursor of androstenedione, and androstenedione is a precursor both of testosterone and of estrogens (see Fig. 30-2). About 50%-60% of testosterone in normal females is derived from androstenedione conversion in peripheral tissues, about 30% is produced directly by the adrenal, and about 20% is produced by the ovary. DHEA blood levels in females are 3 times androstenedione blood levels and about 10 times testosterone blood levels. In normal males after onset of puberty, testosterone blood levels are twice as high as all androgens combined in females. Androstenedione blood levels in males are about 60% of those in females and about 10%-15% of testosterone blood levels.

    Serum testosterone

    About 60%-75% of circulating serum testosterone is bound to a beta globulin variously known as sex hormone-binding globulin (SHBG) or as testosterone-binding globulin (TBG, a misleading abbreviation because of its similarity to the more widely used abbreviation representing thyroxine-binding globulin). About 20%-40% of testosterone is bound to serum albumin and 1%-2% is unbound (“free”). The unbound fraction is the only biologically active portion. Serum assays for testosterone measure total testosterone (bound plus unbound) values. Special techniques to assay free testosterone are available in some reference laboratories and in larger medical centers. Circulating androstenedione and DHEA are bound to albumin only.

    Several conditions can affect total serum testosterone levels by altering the quantity of SHBG without affecting free testosterone. Factors that elevate SHBG levels include estrogens (estrogen-producing tumor, oral contraceptives, or medication), cirrhosis, hyperthyroidism, and (in males) decreased testis function or testicular feminization syndrome. Conditions that decrease SHBG levels include androgens and hypothyroidism.

    There is a relatively small diurnal variation of serum testosterone in men, with early morning levels about 20% higher than evening levels. There is little diurnal change in women. Serum levels of androstenedione in men or women are about 50% higher in the early morning than in the evening.

    In males, testosterone production is regulated by a feedback mechanism with the hypothalamus and pituitary. The hypothalamus produces gonadotropin-releasing hormone (GnRH; also called LHRH), which induces the pituitary to secrete LH (and FSH). LH, in turn, stimulates the Leydig cells of the testis to secrete testosterone.

    Serum estrogens

    There are three major estrogens: estrone ((E1), estradiol (estradiol-17b; E2), and estriol (E3). All of the estrogens are ultimately derived from androgenic precursors (DHEA and androstenedione), which are synthesized by the adrenal cortex, ovaries, or testis. The adrenal is unable to convert androgens to estrogens, so estrogens are directly produced in the ovary or testis (from precursors synthesized directly in those organs) or are produced in nonendocrine peripheral tissues such as the liver, adipose tissue, or skin by conversion of androgenic precursors brought by the bloodstream from one of the organs of androgen synthesis. Peripheral tissue estrogens are derived mainly from adrenal androgens. Estradiol is the predominant ovarian estrogen. The ovary also secretes a much smaller amount of estrone. The primary pathway of estradiol synthesis is from androstenedione to estrone and then from estrone to estradiol by a reversible reaction. This takes place in the ovary and to a much lesser extent in peripheral conversion of testosterone to estradiol. Estrone is produced directly from androstenedione (mostly in peripheral tissues) and to a lesser extent in the ovary from already formed estradiol by the reversible reaction. Estriol in nonpregnant women is formed as a metabolite of estradiol or estrone. In pregnancy, estriol is synthesized by the placenta from DHEA (actually from DHEA-S) derived from the fetal adrenals. This is a different pathway from the one in nonpregnant women. Estriol is the major estrogen of the placenta. The placenta also produces some estradiol, derived from both fetal and maternal precursors. Nonendocrine peripheral tissues (liver, skin, fat) synthesize a small amount of estrone and estradiol in pregnancy, mainly from adrenal precursors.

    In females, there is a feedback mechanism for estradiol production involving the ovaries, hypothalamus, and pituitary. As already mentioned, the hypothalamus produces GnRH. The GnRH is secreted in a pulsatile manner about every 70-90 minutes and is excreted by glomerular filtration. The GnRH stimulates FSH and LH secretion by the pituitary. Some investigators believe there may be a separate (undiscovered) factor that regulates FSH secretion. The FSH acts on the ovarian follicles to stimulate follicle growth and development of receptors to the action of LH. The LH stimulates the follicles to produce estradiol.

    Estradiol values can be measured in serum, and estriol values can be measured in serum or urine by immunoassay. Total estrogen values are measured in urine by a relatively old but still useful procedure based on the Kober biochemical reaction. All of the estrogens can be assayed by gas chromatography. The DHEA and androstenedione values can also be measured by special techniques, but these are available only in large reference laboratories.

  • Acromegaly

    Acromegaly is produced in adults by increase of GH, usually from an eosinophilic adenoma of the pituitary. About two thirds of these patients are female. Signs and symptoms include bitemporal headaches, disturbances of the visual fields, optic nerve atrophy, and physical changes in the face and hands. About 25% of patients have fasting hyperglycemia, and about 50% have decreased carbohydrate tolerance when the oral glucose tolerance test is performed. Serum prolactin is elevated in 25%-40% of patients (literature range, 0%-83%). About 65%-75% of patients with acromegaly display sella turcica enlargement on skull x-ray films. GH assay usually reveals levels above the upper limit of 5 ng/ml. The standard method of confirming the diagnosis is a suppression test using glucose. Normal persons nearly always respond to a large dose of glucose with a decrease in GH levels to less than 50% of baseline, whereas acromegalic patients in theory have autonomous tumors and should show little, if any, effect of hyperglycemia. One study, however, noted relatively normal suppression in a significant percentage of acromegalics. In acromegaly (GH excess), a high somatomedin-C result is diagnostic and is found in nearly all such patients. Other causes of elevated somatomedin-C levels include the adolescent growth spurt and the last trimester of pregnancy. Some investigators believe that somatomedin-C assay is the screening test of choice for acromegaly and that a clear-cut blood level elevation of somatomedin-C might be sufficient for the diagnosis. The major problem is the surge during adolescence.

  • Prolactin Secretion Abnormalities

    Prolactin is another peptide pituitary hormone. It stimulates lactation (galactorrhea) in females, but its function in males is less certain. The major regulatory mechanism for prolactin secretion is an inhibitory effect exerted by the hypothalamus, with one known pathway being under control of dopamine. There is also a hypothalamic stimulating effect, although a specific prolactin-stimulating hormone has not yet been isolated. TRH stimulates release of prolactin from the pituitary as well as release of TSH. Dopamine antagonists such as chlorpromazine or reserpine block the hypothalamic inhibition pathway, leading to increased prolactin secretion. Serum prolactin is measured by immunoassay. Prolactin secretion in adults has a diurnal pattern much like that of GH, with highest levels during sleep.

    Some Conditions Associated With Generalized Retardation or Acceleration of Bone Maturation Compared to Chronologic Age (as Seen on Hand-Wrist X-ray Films
    Bone age retarded
    Hypopituitarism with GH deficiency
    Constitutional growth delay
    Gonadal dysgenesis (Turner’s syndrome)
    Primary Hypothyroidism (20%-30% of patients)
    Cushing’s syndrome
    Severe chronic disease (renal, inflammatory gastrointestinal [GI] disease, malnutrition, chronic
    anemia, cyanotic congenital heart disease)
    Poorly controlled severe type I diabetes mellitus
    Bone age accelerated
    Excess androgens (adrenogenital syndrome; tumor; iatrogenic)
    Excess estrogens (tumor; iatrogenic)
    Albright’s syndrome (polyostotic fibrous dysplasia)
    Hyperthyroidism

    Prolactin assay

    Prolactin-secreting pituitary tumors. Prolactin assay has aroused interest for two reasons. First, about 65% of symptomatic pituitary ad enomas (literature range, 25%-95%), including both microadenomas (<1 cm) and adenomas, produce elevated serum levels of prolactin. The pituitary cell type most often associated with hyperprolactinemia is the acidophil cell adenoma, but chromophobe adenomas (which are by far the most frequent adenoma type) are also involved. In addition, about 20%-30% of women with postpubertal (secondary) amenorrhea (literature range, 15%-50%) have been found to have elevated serum prolactin levels. The incidence of pituitary tumors in such persons is 35%-45%. Many patients have been cured when pituitary adenomas were destroyed or when drug therapy directed against prolactin secretion was given. Hyperprolactinemia has also been reported to be an occasional cause of male infertility.

    Some reports indicate that extension of a pituitary adenoma outside the confines of the sella turcica can be detected by assay of cerebrospinal fluid (CSF) prolactin. Prolactin in CSF rises in proportion to blood prolactin levels but is disproportionately elevated when tumor extension from the sella takes place. A CSF/plasma prolactin ratio of 0.2 or more suggests suprasellar extension of a pituitary tumor. Simultaneously obtained CSF and venous blood specimens are required.

    Not all pituitary tumors secrete prolactin. Autopsy studies have demonstrated nonsymptomatic pituitary adenomas in 2.7%-27% of patients. Theoretically, nonfunctional tumors should have normal serum prolactin levels. Reports indicate, however, that some tumors that do not secrete prolactin may be associated with elevated serum prolactin levels, although the values are usually not as high as levels found with prolactin-secreting tumors.

    Prolactin assay drawbacks. Elevated serum prolactin levels may be associated with conditions other than pituitary tumors, idiopathic pituitary hyperprolactinemia, or hypothalamic dysfunction. Some of these conditions are listed in the box. Especially noteworthy are the empty sella syndrome, stress, and medication. The empty sella syndrome is associated with an enlarged sella turcica on x-ray film. Serum prolactin is elevated in some of these patients, although the elevation is most often not great; and the combination of an enlarged sella plus elevated serum prolactin level could easily lead to a false diagnosis of pituitary tumor. Stress is important since many conditions place the patient under stress. In particular, the stress of venipuncture may itself induce some elevation in serum prolactin levels, so some investigators place an indwelling heparin lock venous catheter and wait as long as 2 hours with the patient resting before the sample is drawn. Estrogens and other medications may contribute to diagnostic problems. In general, very high prolactin levels are more likely to be due to pituitary adenoma than to other causes, but there is a great deal of overlap in the low- and medium-range elevations, and only a minority of pituitary adenomas display marked prolactin elevation. Statistics depend on the diagnostic cutoff level being used. The level of 100 ng/ml (100 µg/L) is most frequently quoted; the majority (45%-81%) of pituitary adenomas are above this level, but only 25%-57% of patients with prolactin levels above 100 ng/ml are reported to have a pituitary adenoma. A value of 300 ng/ml gives clear-cut separation but includes only about one third of the adenomas (literature range, 12%-38%).

    Conditions Associated With Increased Serum Prolactin (% With Elevation Varies)
    Sleep
    Stress (including exercise, trauma, illness)
    Nursing infant
    Pregnancy and estrogens
    Pituitary adenoma
    Hypothalamic space-occupying, granulomatous, or destructive diseases
    Hypothyroidism
    Chronic renal failure
    Hypoglycemia
    Certain medications
    Postpartum amenorrhea syndrome
    Postpill amenorrhea-galactorrhea syndrome
    Empty sella syndrome
    Addison’s disease (Nelson’s syndrome)
    Polycystic ovary (PCO) disease
    Ectopic prolactin secretion (nonpituitary neo-plasms)

    Prolactin stimulation and suppression tests Several stimulation and suppression tests have been used in attempts to differentiate pituitary adenoma from other causes of hyperprolactinemia. For example, several investigators have reported that pituitary adenomas display a normal response to levodopa but a blunted response to chlorpromazine. Normally there is a considerable elevation of prolactin level (at least twofold) after TRH or chlorpromazine administration and a decrease of the prolactin level after levodopa administration. In pituitary insufficiency there typically is failure to respond to TRH, chlorpromazine, or levodopa. In hypothalamic dysfunction there typically is normal response to TRH (which directly stimulates the pituitary), little, if any, response to chlorpromazine, and blunted response to levodopa. Pituitary adenomas are supposed to give a blunted response to TRH and chlorpromazine but a normal decrease with levodopa. Unfortunately, there are sufficient inconsistent results or overlap in adenoma and nonadenoma response that most investigators believe none of these tests is sufficiently reliable. There have also been some conflicting results in differentiating hypothalamic from pituitary disease. Diseases such as hypothyroidism and other factors that affect pituitary function or prolactin secretion may affect the results of these tests.

  • Growth Hormone (GH; Somafotropin) Deficiency

    GH is a peptide that is secreted by the acidophil cells of the pituitary. GH release depends on the interplay between two opposing hormones secreted by the hypothalamus; growth hormone-releasing hormone (GHRH), which stimulates GH release, and somatostatin, which inhibits GH release. GH exerts its effect through stimulation of various tissues to produce a group of peptide growth factors called “somatomedins.” The most important somatomedin is somatomedin-C, which is produced by the liver and which acts on cartilage. High levels of somatomedin participate in a GH feedback mechanism by inhibiting pituitary release of GH and also by stimulating hypothalamic secretion of somatostatin. In addition, there apparently are numerous other factors that influence GH production to varying degree, some of which act through the hypothalamus and others that apparently do not. Normal GH secretion takes place predominantly (but not entirely) during sleep in the form of short irregularly distributed secretory pulses or bursts. GH deficiency most often is suspected or questioned as part of the differential diagnosis of retarded growth or short stature. A considerable number of hormones and factors are necessary for adequate growth. Some of the most important are listed in the box on this page. Etiologies of short stature (whose extreme result is dwarfism) are listed in the box. Diagnosis of many of these conditions is discussed elsewhere. Deficiency of GH will be discussed in the context of pediatric or childhood growth retardation. As noted previously, GH deficiency may be part of multihormone pituitary dysfunction but may exist as an isolated defect in an otherwise apparently normal pituitary.

    GH deficiency tests

    Growth hormone assay. The most widely used screening test for GH deficiency is serum GH assay. Values are elevated by sleep, exercise of any type, and various foods. Therefore, if a single basal level is obtained, the specimen should be secured in the morning after an overnight fast, and the patient should be awake but not yet out of bed. Because basal normal range for single specimens includes some normal persons with values low enough to overlap the range of values found in patients with GH deficiency, only a result high enough to rule out GH deficiency is significant. Low results either may be due to GH deficiency or may simply be low-normal. Other conditions that increase GH levels besides those previously mentioned include severe malnutrition and chronic liver or renal disease. Patients with psychiatric depression or poorly controlled diabetes mellitus secrete more GH than normal persons during waking hours but not during sleep.

    Body Factor Snecessary for Normal Growth
    GH
    Somatomedins
    Insulin
    Thyroxine
    Sex hormones
    Adequate nutritional factors
    Partial List of Short Stature Etiologies
    Familial short stature
    Constitutional growth delay
    Turner’s syndrome
    Trisomy syndromes (e.g., Down’s syndrome)
    GH deficiency (isolated or hypopituitarism)
    Hypothyroidism
    Severe malnutrition
    Malabsorption
    Uncontrolled type I diabetes mellitus
    Severe chronic illness with organ failure (chronic renal disease, congenital heart disease, severe chronic hemolytic anemia)
    Excess androgens or estrogens
    Excess cortisol (Cushing’s syndrome or iatrogenic)
    Psychosocial retardation (abused or severely emotionally deprived children)

    Two relatively simple screening tests for GH deficiency have been advocated. It has been found that a major part of daily GH secretion takes place in a short period beginning approximately 1 hour after onset of deep sleep (electro-encephalogram [EEG] stage 3 or 4). Therefore, one method is to observe the patient until deep sleep occurs, wake the patient 60-90 minutes later, and quickly draw a blood sample for GH assay. About 70% of normal children or adults have GH values sufficiently elevated (і7 ng/ml; 7 µg/L) to exclude GH deficiency. Strenuous exercise is a strong stimulus to GH secretion. An exercise test in which the patient exercises vigorously for 20-30 minutes and a blood sample is drawn for GH assay 20-30 minutes after the end of the exercise period has been used. About 75%-92% of normal children have sufficiently elevated levels of GH after exercise to exclude GH deficiency.

    A third method involves integrated multihour time period blood specimens; this method is being used in research and in some medical centers. Because of the irregular pulsatile nature of GH secretion, it was found that a more reliable estimate of GH secretion levels could be obtained by drawing blood specimens for GH assay every 20-30 minutes from an indwelling catheter over a 24-hour period. Some investigators report that the same information can be obtained using an 8 P.M. -8 A.M. 12-hour period while the patient is sleeping. The integration (averaging) of the GH specimen values correlate much better with clinical findings, especially in patients with partial GH deficiency (also known as “neurosecretory GH deficiency”), than does a single-specimen value. This test is being used when standard tests are equivocal or normal in spite of clinical suspicion of GH deficiency.

    Somatomedin-C assay. Somatomedin-C assay has been proposed as a screening test for GH deficiency, pituitary insufficiency, and acromegaly. As noted previously, somatomedin serum levels depend on serum GH levels, and it has been postulated that the growth-promoting actions of GH are actually carried out by the somatomedins. Somatomedin-C is produced in the liver and circulates in serum predominantly bound to certain long-lived high molecular weight serum proteins. Normal values for females are about 10%-20% higher than those for males in both children and adults. Normal values also depend on age and developmental stage. There is a considerable increase during the pubertal adolescent growth spurt. Radioreceptor and immunoassay measurement techniques are available in large reference laboratories for somatomedin-C. Serum levels are low in most patients with isolated GH deficiency or pituitary insufficiency. The assay has some advantages in that the result does not depend on relation to food intake or time of day. Disadvantages are that only large medical centers or reference laboratories offer the assay and that various conditions besides pituitary dysfunction may produce a low result. These nonpituitary conditions include decreased caloric intake and malnutrition, malabsorption, severe chronic illness of various types, severe liver disease, hypothyroidism, and Laron dwarfism. Therefore, a clearly normal result is more diagnostic than a low result, since the low result must be confirmed by other tests. Somatomedin-C levels are elevated in acromegaly (discussed later).

    Growth hormone stimulation tests. Since only a clearly normal single-specimen GH result excludes pituitary GH secretion deficiency, in patients with lower single-specimen GH values a stimulation test is needed for detection of deficiency or confirmation of normality. The classic procedures are insulin-induced hypoglycemia and arginine infusion. Pituitary insufficiency cannot be documented on the basis of pituitary nonresponse to either test agent alone, since about 20% of normal persons may fail to respond satisfactorily to insulin alone or to arginine alone. Estrogen administration tends to increase GH secretion, and some investigators have obtained better results from arginine infusion after administration of estrogens.

    Stimulation tests with other substances, including glucagon, tolbutamide, levodopa, and clonidine, have been proposed. Of these, levodopa stimulation seems to give best results; some believe that it has an accuracy equal to or better than that achieved with insulin or arginine stimulation and, in addition, is easier and safer to perform. One investigator found a greater number of unreliable results in older persons and depressed patients. Blood samples are drawn 60 and 90 minutes after oral levodopa administration. Investigators have explored various means to improve the accuracy of these tests. Sympathetic nervous system alpha-adrenergic stimulants enhance GH release while beta stimulation is inhibitory. The beta blocker propranolol, given with levodopa, enhances levodopa stimulation of GH secretion and improves identification of normal persons. For example, one investigator reported only about 5% false low GH results with the combination of levodopa and propranolol but 20% false low results with levodopa alone. Clonidine stimulation has attracted interest because it has fewer side effects and is more convenient to perform than the other tests. However, there is disagreement regarding test accuracy, partially because some investigators used lower doses that did not provide maximal effect. Overall effectiveness with higher doses is said to be similar to that of the other stimulation tests. The major problems with the stimulation tests are the need for more than one test to confirm a failure to stimulate GH levels and the existence of partial (neurosecretory) GH secretion deficiency, in which GH secretion is not sufficient for normal bone growth but stimulation test results are normal. At present, the diagnosis of partial GH deficiency is made through 12-hour or 24-hour integrated GH measurements or by therapeutic trial with GH. GHRH is now available for investigational use. Preliminary reports using GHRH as a stimulation test in GH deficiency have yielded results rather similar to those of standard stimulatory tests. GHRH testing may be useful in differentiating hypothalamic dysfunction from pituitary GH dysfunction. However, some patients with hypothalamic dysfunction may show apparent failure to respond to initial stimulation of the pituitary by GHRH, thus simulating pituitary GH secretory dysfunction, although they respond normally after repeated stimulation.

    Bone X-ray studies. Hand-wrist x-ray studies for bone age (bone maturation) are strongly recommended in patients with suspected growth disorders. The actual genetic sex (which in some instances may be different from the apparent sex) must be furnished to the radiologist so that the correct reference range may be used. Bone maturation should be compared with linear growth (height) and chronologic age. The box on this page lists some conditions associated with retarded or accelerated bone age.

  • Pituitary Insufficiency

    Body organs affected by stimulatory hormones from the pituitary include the thyroid, adrenals, and gonads. Bone growth in childhood is dependent on pituitary GH. Pituitary failure does not produce a clear-cut syndrome analogous to syndromes produced by failure of pituitary-controlled organs (“end organs”) such as the thyroid. Therefore, pituitary hormone deficiency is considered only when there is deficiency-type malfunction in one or more end organs or metabolic processes such as growth that are dependent on pituitary hormones. Diagnosis is complicated by the fact that primary end organ failure is much more common than pituitary hormone deficiency. Another source of confusion is that most abnormal effects that can be produced by pituitary dysfunction can also be produced or simulated by nonpituitary etiologies. In addition, the hypothalamus controls pituitary secretion of several hormones, so that hypothalamic abnormality (e.g., defects produced by a craniopharyngioma or other hypothalamic tumor) can result in pituitary dysfunction.

    Pituitary insufficiency in adults most commonly results in deficiency of more than one pituitary hormone and is most frequently caused by postpartum hemorrhage (Sheehan’s syndrome). Pituitary tumor is also an important cause. Gonadal failure is ordinarily the first clinical deficiency to appear. It is followed some time later by hypothyroidism. The first laboratory abnormality is usually failure of the GH level to rise normally in response to stimulation.

    Diagnosis

    Diagnosis of pituitary insufficiency can be made by direct or indirect testing methods. Indirect methods demonstrate that a hypofunctioning organ that is pituitary dependent shows normal function after stimulation by injection of the appropriate pituitary hormone. Direct methods consist of blood level assays of pituitary hormones. Another direct method is injection of a substance that directly stimulates the pituitary. Now that pituitary hormone assays are available in most medical centers and sizable reference laboratories, indirect tests are much less frequently needed.

    Assay of pituitary hormones. Pituitary hormones are peptide hormones rather than steroid hormones. Currently available immunoassays are a great improvement over original bioassays and even the first-generation radioimmunoassays (RIAs). However, with the exception of thyroid-stimulating hormone (TSH), pituitary hormone assays are still ordered infrequently, so that most physician’s offices and ordinary hospital laboratories do not find it economically worthwhile to perform the tests. The assays for TSH and adrenal cortex stimulating hormone (adrenocorticotropin; ACTH) are discussed in the chapters on thyroid and adrenal function. Pituitary luteinizing hormone (LH) and follicle-stimulating hormone (FSH) assay are discussed later. GH deficiency is probably the most frequent pituitary hormone deficiency, either in overall pituitary failure or as an isolated defect leading to growth retardation in childhood. GH assay will be discussed in detail in relation to childhood growth disorders. GH assay has been used as an overall screen for pituitary insufficiency, but not all cases of pituitary hormone secretion deficiency have associated GH secretion deficiency. Prolactin is another pituitary hormone, but prolactin secretion is one of the last pituitary functions to disappear when the pituitary is injured.

    In primary end organ failure the blood level of stimulating hormone from the pituitary is usually elevated, as the pituitary attempts to get the last possible activity from the damaged organ. Therefore, in the presence of end organ failure, if values for the pituitary hormone that stimulates the organ are in the upper half of the reference range or are elevated, this is strong evidence against deficiency of that pituitary hormone. Theoretically, inadequate pituitary hormone secretion should result in serum assay values less than the reference range for that pituitary hormone. Unfortunately, low-normal or decreased values of some pituitary hormones may overlap with values found in normal persons, at least using many of the present-day commercial assay kits. In that situation, stimulation or suppression testing may be necessary for more definitive assessment of pituitary function.

    Stimulation and suppression tests. Pituitary suppression and stimulation tests available for diagnosis of pituitary hormone secretion deficiency include the following:

    1. Metyrapone (Metopirone) test based on the adrenal cortex-pituitary feedback mechanism involving ACTH and cortisol but dependent also on hypothalamic function.
    2. Thyrotropin-releasing hormone (TRH) test involving the ability of synthetic TRH to stimulate the pituitary by direct action to release TSH and prolactin.
    3. Tests involving pituitary gonadotropins (LH and FSH) such as clomiphene stimulation (involving the hypothalamic-pituitary axis) or LH-releasing hormone (LHRH) administration (direct pituitary stimulation).
    4. Tests of hypothalamic function, usually based on establishing pituitary normality by direct stimulation of the pituitary (TRH stimulation of TSH and prolactin, LHRH stimulation of LH secretion, etc.) followed by use of a test that depends on intact hypothalamic function to stimulate pituitary secretion of the same hormone. An example is the use of TRH to stimulate prolactin secretion by the pituitary, followed by chlorpromazine administration, which blocks normal hypothalamic mechanisms that inhibit hypothalamic stimulation of pituitary prolactin secretion and which leads to increased prolactin secretion if the hypothalamus is still capable of stimulating prolactin release.

  • Adrenal and Nonadrenal Causes of Hypertension

    Cushing’s syndrome, primary aldosteronism, unilateral renal disease (rarely, bilateral renal artery stenosis), and pheochromocytoma often produce hypertension. Hypertension due to these diseases is classified as secondary hypertension, in contrast to primary idiopathic (essential) hypertension. Although patients with these particular diseases that cause secondary hypertension are a relatively small minority of hypertension patients, the diseases are important because they are surgically curable. The patient usually is protected against the bad effects of hypertension by early diagnosis and cure. Patients who must be especially investigated are those who are young (less than age 50 years), those whose symptoms develop over a short time, or those who have a sudden worsening of their hypertension after a previous mild stable blood pressure elevation.

  • Adrenal Medulla Dysfunction

    The only syndrome in this category is produced by pheochromocytomas. Pheochromocytoma is a tumor of the adrenal medulla that frequently secretes epinephrine or norepinephrine. This causes hypertension, which may be continuous (about 30% of patients) or in short episodes (paroxysmal). Although rare, pheochromocytoma is one of the few curable causes of hypertension and so should be considered as a possible etiology in any patient with hypertension of either sudden or recent onset. This is especially true for young or middle-aged persons.

    Approximately 90% of pheochromocytomas in adults arise in the adrenal (more often in the right adrenal). Of the 10% that are extraadrenal, the great majority are located in the abdomen, with 1%-2% in the thorax and neck. Extraadrenal abdominal tumors are usually found in the paraaortic sympathetic nerve chain (below the level of the renal artery), but perhaps one third are located in the remnants of the organ of Zuckerkandl (which is situated in the paraaortic region between the origin of the inferior mesenteric artery and the bifurcation of the aorta). About 20% of pheochromocytomas are multiple and about 10% are bilateral. Approximately 5%-10% (range, 3%-14%) of all pheochromocytomas are malignant, but the malignancy rate for extraadrenal abdominal tumors is reported to be about 25%-30%. Although hypertension is the most common significant clinical finding, 10%-20% of pheochromocytomas do not produce hypertension (Table 30-3). Hyperglycemia is reported in about 50% of patients. In one autopsy series of 54 cases, only 25% were diagnosed during life.

    Common signs and symptoms of pheochromocytoma

    Table 30-3 Common signs and symptoms of pheochromocytoma

    About 5% of pheochromocytoma patients have neurofibromatosis, and in 5%-10% the pheochromocytoma is associated with the multiple endocrine neoplasia (MEN) syndrome type II (also known as “IIA,” with medullary carcinoma of the thyroid) or III (also known as “IIB,” with mucosal neuromas). The MEN syndrome pheochromocytomas are bilateral in 50%-95% of cases and multiple in about 70% of cases, whereas nonfamilial (sporadic) pheochromocytomas are usually unilateral and are multiple in about 20% of cases. About 5% of the familial cases are said to be malignant.

    In children, extraadrenal pheochromocytomas are more common (30% of cases), more often bilateral (25%-70% of cases), and more often multiple (about 30% of cases) than in adults. About 10%-20% of adrenal or extraadrenal childhood pheochromocytomas are reported to be malignant.

    Tests for pheochromocytoma

    Regitine test. The first tests for pheochromocytomas were pharmacologic, based on neutralization of epinephrine effects by adrenergic-blocking drugs such as Regitine. After basal blood pressure has been established, 5 mg of Regitine is given intravenously, and the blood pressure is checked every 30 seconds. The result is positive if systolic blood pressure decreases more than 35 mm Hg or diastolic pressure decreases 25 mm Hg or more and remains decreased 3-4 minutes. Laboratory tests have proved much more reliable than the pharmacologic procedures, which yield an appreciable percentage of false positives and negatives.

    Clonidine suppression test. Clonidine is a centrally acting alpha-adrenergic agonist that inhibits sympathetic nervous system catecholamine release from postganglionic neurons. The patients should not be on hypertensive medication (if possible) for at least 12 hours before the test. After a baseline blood specimen is obtained, a single 0.3-mg oral dose of clonidine is administered and a second blood specimen is drawn 3 hours later. Most patients without pheochromocytoma had postdose plasma norepinephrine values more than 50% below baseline and plasma catacholamine values less than 500 pg/ml. Most patients with pheochromocytoma showed little change in plasma norepinephrine values between the predose and postdose specimens and had a plasma catacholamine postdose level greater than 500 pg/ml. Apparently, better results are obtained when baseline urine norepinephrine values are greater than 2000 pg/ml (86%-99% sensitivity) than when the baseline value is less than 2000 pg/ml (73%-97% sensitivity). Medication such as tricyclic antidepressants, thiazide diuretics, and beta blockers may interfere with the test.

    Catecholamine/vanillylmandelic acid/metanephrine assay. The catecholamines epinephrine and norepinephrine are excreted by the kidney, about 3%-6% free (unchanged), and the remainder as various metabolites. Of these metabolic products, the major portion is vanillylmandelic (vanilmandelic) acid (VMA), and the remainder (about 20%-40%) is compounds known as metanephrines. Therefore, one can measure urinary catecholamines, metanephrines, or VMA. Of these, urine metanephrine assay is considered by many to be the most sensitive and reliable single test. There are also fewer drugs that interfere.

    Most investigators report that urine metanephrine assay detects about 95% (range, 77%-100%) of patients with pheochromocytoma. Sensitivity of urine catecholamines is approximately 90%-95% (range, 67%-100%) and that of urine VMA assay is also about 90%-95% (range, 50%-100%). One report indicates that metanephrine excretion is relatively uniform and that a random specimen reported in terms of creatinine excretion can be substituted for the usual 24-hour collection in screening for pheochromocytoma. Methylglucamine x-ray contrast medium is said to produce falsely normal urine metanephrine values for up to 72 hours. One report found that 10%-15% of mildly elevated urine metanephrine values were falsely positive due to medications (such as methyldopa) or other reasons.

    Although the metanephrine excretion test is slowly gaining preference, VMA and catecholamine assay are still widely used. All three methods have detection rates within 5%-10% of one another. A small but significant percentage of pheochromocytomas are missed by any of the three tests (fewer by metanephrine excretion), especially if the tumor secretes intermittently. The VMA test has one definite advantage in that certain screening methods are technically more simple than catecholamine or metanephrine assay and therefore are more readily available in smaller laboratories. The VMA screening methods are apt to produce more false positive results, however, so that abnormal values (or normal results in patients with strong suspicion for pheochromocytoma) should be confirmed by some other procedure.

    Catecholamine production and plasma catecholamine levels may be increased after severe exercise (although mild exercise has no appreciable effect), by emotional stress, and by smoking. Uremia interferes with assay methods based on fluorescence. Other diseases or conditions that may increase plasma or urine catecholamines or urine catecholamine metabolites are hypothyroidism, diuretic therapy, heavy alcohol intake, hypoglycemia, hypoxia, severe acidosis, Cushing’s syndrome, myocardial infarction, hemolytic anemia, and occasionally lymphoma or severe renal disease. In addition, bananas, coffee, and various other foods as well as certain medications may produce falsely elevated results. These foods or medications produce appreciable numbers of false-positive results in some of the standard screening techniques for VMA. An abnormal result with the “screening” VMA techniques should be confirmed by some other VMA method. Although other VMA methods or methods for metanephrine and catecholamine assay are more reliable, they too may be affected by certain foods or medications, so it is best to check with individual laboratories for details on substances that affect their particular test method. Reports differ on whether some patients with essential hypertension may have elevated serum or urine catecholamine or catecholamine metabolite results; and if so, how often it occurs and what percentage are due to conditions known to elevate catecholamines, or to medications, or to unknown causes.

    Some investigators use urine fractionated catecholamines (epinephrine and norepinephrine, sometimes also dopamine) by high-pressure liquid chromatography as a confirmatory test for pheochromocytoma. It is said that about 50%-70% of pheochromocytomas produce epinephrine, about 75%-85% produce norepinephrine, and about 95% produce one or the other.

    Plasma catecholamine assay. Several investigators report better sensitivity in pheochromocytoma with plasma catecholamine assay than with the particular urine metabolite assays they were using. Another advantage is the simplicity of a single blood specimen versus 24-hour collection. However, upright posture and stress can greatly affect plasma catecholamine levels, even the stress of venipuncture, so it is best to draw the specimen in the early morning before the patient rises. Even then, some advocate placement of an indwelling venous catheter or heparinized scalp vein apparatus with an interval of 30 minutes between insertion of the catheter and withdrawal of the blood specimen. One investigator reported that plasma catecholamine values decreased rapidly if the red blood cells (RBCs) were not removed within 5 minutes after obtaining the specimen. Placing the specimen on ice was helpful but only partially retarded RBC catecholamine uptake. Plasma catecholamine assay detection rate in pheochromocytomas is about 90% (literature range, 53%-100%). Failure to detect the tumor in some instances is due to intermittent tumor secretion. Urine collection has the advantage of averaging the 24-hour excretion.

    Tumor localization methods. Once pheochromocytoma is strongly suspected by results of biochemical testing, certain procedures have been useful in localizing the tumor. Intravenous pyelography with nephrotomography is reported to have an accuracy of about 70% in detecting adrenal pheochromocytoma. CT has been reported to detect 85%-95% (range, 84%-over 95%) of pheochromocytomas, including some in extraadrenal locations. Consensus now is that CT (or magnetic resonance imaging [MRI]) is the best single localization test (better than ultrasound). Radioactive mIBG has been used to locate pheochromocytomas and other neural tumors with sensitivity of about 85%. However, this procedure is only available in a very few nuclear medicine centers. Angiographic procedures are reported to detect 60%-84% of pheochromocytomas; but angiography is somewhat controversial because it is invasive, because it yields about 10% false negative results in adrenal tumors, and because some investigators believe that the incidence of tumor bilaterality warrants exploration of both sides of the abdomen regardless of angiographic findings.

    Miscellaneous procedures. Serum chromogranin A (CgA), a substance produced in the adrenal medulla and some other endocrine and neuroendocrine tissues and tumors, has been used in diagnosis of pheochromocytoma. CgA is not affected by posture, venipuncture, and many medications that interfere with catecholamine assay; in one series CGA detected 86% of pheochromocytomas.

    Deoxyribonucleic acid (DNA) analysis by flow cytometry in small numbers of patients suggest that pheochromocytomas with diploid ploidy are most often (but not always) benign, whereas those that are aneuploid are most often (but not always) malignant.

    Serum neuron-specific enolase (NSE) in small numbers of patients suggest that pheochromocytomas with normal NSE levels are usually benign, but those with elevated values are often malignant.