Effect of thyrotropin-releasing hormone on gastric acid secretion in man

Thyrotropin-releasing hormone (TRH) has been shown to have a dose-dependent inhibiting effect on the pentagastrin-stimulated gastric acid secretion in man. We studied the effect of increasing doses of TRH on the gastric acid secretion stimulated by a submaximal histamine dose. The effect of a relatively high dose of TRH (500 micrograms/h) on the maximal histamine-stimulated acid secretion was examined. Furthermore, we studied the effect of two doses of TRH (40 micrograms/h and 500 micrograms/h) on the gastric acid output after insulin-induced hypoglycemia. A significant reduction of the submaximal histamine-stimulated gastric acid output was observed during infusion of 8 micrograms/h TRH (16%), 40 micrograms/h TRH (38%), and 200 micrograms/h TRH (42%) (percentage reduction compared with the control experiment). TRH, 1000 micrograms/h, had no significant effect. With regard to the acid output after maximal histamine stimulation, TRH 500 micrograms/h was without significant effect. After hypoglycemia the acid output was reduced by 30% during 40 micrograms/h TRH (p less than 0.05) and by 37% during 500 micrograms/h TRH (p less than 0.02). TRH had no effect on the acid concentration in any of the studies. The possible mechanisms by which TRH may interact with the acid regulation are discussed.