Radioimmunoassay measurements of serum thyrotropin in patients with hypothalamic-pituitary and thyroid diseases

Serum TSH was measured by means of double antibody radioimmunoassay using a commercial Kit Daiichi, in 21 normal subjects, 200 patients with thyroid disease and 130 patients with hypothalamic-pituitary diseases. Serum TSH concentrations in normal subjects were <2 to 8 μU/ml which rose to 8-40 μU/ml after administration of 500 μg TRH intravenously. Serum TSH was undetectable and did not respond to TRH in all untreated patients and in some euthyroid patients with Graves' disease after treatment. Undetectable TSH and no response to TRH were also observed in most patients with a hyperfunctioning thyroid nodule and those with subacute thyroiditis in the acute phase. In some patients with Hashimoto's thyroiditis and all patients with adult myxedema and cretinism, serum TSH levels were increased and showed hyperresponse to TRH. The ratio of bioassay and radioimmunoassay potency estimates for TSH in sera obtained before TRH was not statistically different from that obtained after TRH administration to patients with primary hypothyroidism. Elevated serum TSH was promptly decreased by the administration of thyroid hormone to the patients. More than 50% of patients with pituitary adenoma, acromegaly and craniopharyngioma showed normal basal TSH and no or low response of TSH to TRH. Administration of TRH failed to stimulate a rise in serum TSH in 2 sisters with isolated TSH deficiency with cretinism. Basal TSH was undetectable and showed delayed response to TRH in patients with anorexia nervosa. (auth.)