Congenital hypothyroidism occurs in approximately 1 in 6,000 infants (literature range, 1-3/10,000), which makes it about 3 times as common as phenylketonuria (PKU). Approximately 85% of cases are due to thyroid agenesis and 10% are defects of enzymes in thyroid hormone synthesis, so that about 95% of all cases are primary hypothyroidism and 3%-5% are […]
Thyrotropin stimulation test. In some patients with myxedema, the question arises as to whether the etiology is primary thyroid disease or a malfunction secondary to pituitary deficiency. Normally, administration of TSH more than doubles a baseline RAIU or T4 value. Failure of the thyroid to respond to TSH stimulation strongly suggests primary thyroid failure, whereas […]
Thyrotropin previously was known as thyroid stimulating hormone (TSH), and the abbreviation TSH is still used. Direct assay of TSH is now possible with commercially available kits that are as easy to use as those for T4 assay. Thyrotropin has a diurnal variation of 2 to 3 times baseline (literature range, 33%-600%), with highest levels […]
