Triiodothyronine response to thyrotrophin releasing hormone in patients with hypothalamic-pituitary disorders.
The serum triiodothyronine concentration was evaluated before and after thyrotrophin releasing hormone in fifty-six patients with hypothalamic-pituitary disorders (thirty-four had secondary hypothyroidism, twenty-two were euthyroid) and in twenty-four normal controls. Basal serum T3 was low in fifteen hypothyroid subjects and normal in the remainders. After TRH, serum T3 did not increase normally in twenty-five hypothyroid and in ten euthyroid patients; even the patients with normal or supranormal plasma TSH increase had significantly lower T3 responses than normal controls (P less than 0-0001 for hypothyroid, P less than 0-01 for euthyroid subjects). The finding of low T3 response to TRH in some euthyroid patients with hypothalamic-pituitary disorders can perhaps identify cases of preclinical secondary hypothyroidism, probably due to low biological activity of released TSH.
D002986:Clinical Trials as Topic; D005260:Female; D006801:Humans; D007037:Hypothyroidism / Q000097:blood*; D008297:Male; D010900:Pituitary Diseases / Q000097:blood*; D013972:Thyrotropin / Q000097:blood; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology*; D014284:Triiodothyronine / Q000097:blood*
D014284:Triiodothyronine; D013973:Thyrotropin-Releasing Hormone; D013972:Thyrotropin