BROMOCRIPTINE SUPPRESSION OF TRH-STIMULATED PROLACTIN AND THYROTROPHIN RELEASE AND ACCOMPANYING INHIBITION OF BROMOCRIPTINE INDUCED GROWTH HORMONE RELEASE BY TRH IN NORMAL MAN

Abstract

Six normal fasting males received on 4 separate occasions in random order a placebo tablet followed 60 min later by 200 .mu.g of TRH [thyrotropin releasing hormone], i.v. bromocriptine 2.5 mg orally followed by TRH i.v., bromocriptine 2.5 mg orally followed by a placebo injection and placebo tablet followed by placebo injection. Plasma prolactin and TSH [thyrotropin] responses to TRH were decreased following bromocriptine pretreatment. The rise of plasma growth hormone after bromocriptine was inhibited by TRH. The rise in plasma FSH [follicle stimulating hormone] seen after TRH injection was not influenced by bromocriptine pretreatment. Circulating LH [luteinizing hormone] and insulin concentrations were unaffected by any drug administration. These results suggest a dopaminergic influence on prolactin and TSH release in normal men, an inhibitory effect of TRH on bromocriptine stimulated growth hormone secretion and no dopaminergic modulation of basal insulin secretion.