Effect of bromoergocriptine on TRH-induced growth hormone and prolactin release in acromegalic patients

In an attempt to evaluate the dynamics of growth hormone (GH) and prolactin secretion in acromegalic patients, the response of serum GH as well as prolactin to 2-bromo-alpha-ergocriptine (CB154) alone or to CB154 combined with thyrotropin-releasing hormone (TRH) was studied in 8 subjects with this disease. Oral administration of CB154 unequivocally decreased serum prolactin levels in all of the 8 patients, while GH-inhibitory action of the drug was observed only in 6 subjects who responded to TRH with secretion of GH. The response of serum GH to TRH was not qualitatively and quantitatively altered by the treatment of patients with CB154 in a daily dose of 5 mg for two weeks. This treatment, on the other hand, remarkably suppressed basal levels of prolactin and completely blocked TRH-induced prolactin release in all of the subjects. The results suggest that there exists a dissociation between GH and prolactin responses to CB154 in acromegalic patients, and that CB154 and TRH may not share a common site of action on GH release in this pathologic state.