A B S T R A C T To determine if propylthiouracil (PTU)inhibited extrathyroidal thyroxine (T4) to triiodothyronine (Ts) conversion in man, PTU was administered to T4-treated hypothyroid patients and serial measurements of T4, T3, and thyrotropin (TSH) carried out. All patients had proven thyroidal hypothyroidism and had been receiving 0.1 or 0.2 mg T4 daily for at least 2 mo before study. Hormone measurements were made for 5 consecutive days before and daily during a 7-day treatment period with PTU, 1,000 mg/day.In eight patients receiving 0.1 mg T4 daily, administration of PTU resulted in a prompt fall in mean serum T3 concentrations from 78±6 ng/100 ml (SEM) to 61±3 ng/100 ml after 1 day. The mean serum Ts concentrations ranged from 55 to 60 ng/100 ml during the remainder of the PTU treatment period (P < 0.01):The mean control serum TSH concentration was 29.6 AU/ml and it increased to a peak of 40 /U/ml on the 5th and 6th days. In five patients receiving 0.2 mg T4 daily, the mean control serum Ta concentration was 84±7 ng/ 100 ml. It fell to 70+5 ng/100 ml after 1 day and 63±7 ng/100 ml after 2 days of PTU administration and thereafter ranged from 61 to 69 ng/100 ml (P < 0.01
A 51-year-old man who had a pituitary adenoma that appeared to be hypersecreting LH and FSH is described. Not only were serum LH and FSH concentrations above the normal ranges, but the serum concentrations of testosterone, free testosterone, and dihydrotestosterone were also above normal. Serum LH and FSH concentration increased in response to synthetic thyrotropin-releasing hormone as well as to synthetic gonadotropin-releasing hormone. The elevated hormone concentrations decreased following an initial partial hypophysectomy and decreased further following repeat hypophysectomy.
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