TRH-Gly, a precursor of TRH, alters GH secretion in acromegaly.

We explored effects of a precursor of thyrotropin (TSH)-releasing hormone (TRH), TRH-Gly, on growth hormone (GH) secretion in acromegaly. Intravenous injection of TRH-Gly produced a profound increase in GH secretion in eight, decrease in two, and no response in five out of a total fifteen patients. The magnitude of GH responsiveness to TRH-Gly was significantly correlated with that induced by TRH (r = 0.824, P less than 0.01). In contrast, TRH-Gly did not induce secretion of TSH or prolactin. The present data suggest that TRH-Gly may participate in regulating GH secretion in some patients with acromegaly and that TRH-Gly-induced GH secretion may be due at least in part to TRH-associated mechanisms underlying GH secretion.