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 remainder. 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