Lack of effect of thyroid hormones on the growth hormone response to thyrotropin-releasing hormone in acromegaly.

Serum growth hormone (GH) responses to thyrotropin-releasing hormone (TRH) were evaluated in 14 patients with acromegaly following treatment with thyroid hormones. After an initial TRH test, seven patients received L-triiodothyronine, 100 mug daily for seven days; the GH response to TRH was not significantly altered by this treatment. Similar findings were noted in two acromegalic subjects who were tested with TRH before and after longer periods of administration of L-thyroxine. Four of five additional subjects with acromegaly who had received replacement doses of thyroid hormones for an average of 6.6 yr demonstrated GH responses to TRH which were similar to those seen in subjects not receiving thyroid hormones. Acute or long-term administration of replacement doses of thyroid hormones seems to have minimal effect on the GH response to TRH in acromegaly.