Various studies have shown that a significant degree of malnutrition is frequent in hospitalized persons, ranging from 25%-50% of patients (depending on whether the population screened was a general or specialty group). In one report, 97% of surgical patients had at least one abnormal result on tests for nutritional status.
Classification of protein-calorie malnutrition
Although protein or [...]
Zinc
Zinc is a component of certain important enzymes, such as carbonic anhydrase, lactic dehydrogenase, alkaline phosphatase, DNA and RNA polymerases, and d-aminolevulinic acid dehydratase. Zinc is obtained primarily through food. About 30% of that ingested is absorbed in the small intestine. About 80% of zinc in blood is found in RBCs, mostly as part of [...]
Phosphorus and phosphate are often spoken of interchangeably, although phosphorus is only one component of phosphate. The semantic problem is even more confusing because an order for “phosphate” assay usually results in laboratory measurement of inorganic phosphorus. However, much of the body phosphorus is a part of phosphate compounds. About 80%-85% of body phosphorus is [...]
Magnesium is the fourth most common body cation (after sodium, potassium, and calcium) and the second most common intracellular cation (after potassium). About half is located in soft tissue and muscle cells and about half is in bone. Only 1%-5% is extracellular. Most body magnesium is derived from food intake. About one third of dietary [...]
Hypocalcemia may be subdivided into nonionized hypocalcemia (decrease in serum total calcium value) and true hypocalcemia (decrease in ionized calcium value).
Selected Etiologies of Hypocalcemia
Artifactual
Hypoalbuminemia
Hemodilution
Primary hypoparathyroidism
Pseudohypoparathyroidism
Vitamin D-related
Vitamin D deficiency
Malabsorption
Renal failure
Magnesium deficiency
Sepsis
Chronic alcoholism
Tumor lysis syndrome
Rhabdomyolysis
Alkalosis (respiratory or metabolic)
Acute pancreatitis
Drug-induced hypocalcemia
Large doses of magnesium sulfate
Anticonvulsants
Mithramycin
Gentamicin
Cimetidine
The most common cause of nonionized (“laboratory”) hypocalcemia is a decrease in the serum albumin [...]
Since many patients (50% or more) with cancer and hypercalcemia do not have demonstrable bone metastases or PHPT, it has long been suspected that the cancer could be producing a parathyroid hormonelike substance. The parathyroid hormone-related protein (PTHrP) molecule has a C-terminal end and an N-terminal end like PTH; in addition, a portion of the [...]
In confirmed hypercalcemia, differential diagnosis is usually among PHPT, malignancy (metastatic to bone or the ectopic PTH syndrome), and all other etiologies. In most cases the differential eventually resolves into PHPT versus hypercalcemia of malignancy (HCM). There is no single laboratory test that can distinguish between PHPT and HCM every time with certainty. As noted [...]
PTH is secreted in a discontinuous (pulsatile) fashion. There is a diurnal variation, with highest values at 2 A.M. (midnight to 4 A.M.) and lowest at noon (10 A.M. -2 P.M.. The parathyroids synthesize intact PTH, consisting of 84 amino acids in a single chain. Metabolic breakdown of intact PTH occurs both inside and outside [...]
Serum calcium. Routine serum calcium assay measures the total serum calcium value. Total serum calcium contains about 50% bound calcium (literature range, 35%-55%) and about 50% nonbound calcium (literature range, 35%-65%). (Traditionally, nonbound calcium was called “ionized” calcium and is also known as “free” or “dialyzable” calcium.) Bound calcium is subdivided into calcium bound to [...]
PHPT is caused by overproduction or inappropriate production of PTH by the parathyroid gland. The most common cause is a single adenoma. The incidence of parathyroid carcinoma is listed in reviews as 2%-3%, although the actual percentage is probably less. About 15% (possibly more) of cases are due to parathyroid hyperplasia, which involves more than [...]
