Objective: Serotoninergic receptors are involved in the regulation of PRL and GH secretion. We studied the effects of sumatriptan, a new 5-HT1D receptor agonist, on PRL and GH secretion in active acromegaly.
Experimental design: After their informed consent, all subjects were submitted to sumatriptan or placebo administration in single blind and in a random order. The time interval between the tests was of 7 days.
Environment: We examined all patients in the morning, after 12 hours of fasting. All subjects were in recumbent position during the tests. Pulse rate and blood pressure were monitored during the test.
Subjects: Eight acromegalics (42-65 years) and 10 age-matched (33-63 years) normal subjects.
Protocol: Blood samples were taken after needle insertion kept patent by slow saline solution infusion. PRL and GH secretion were evaluated after sumatriptan (6 mg sc) and placebo. Blood samples were taken before (45, 15 and 0 minutes) and every 15 minutes for 2 hours after sumatriptan or placebo administration.
Results: No significant changes in PRL secretion were observed after sumatriptan in both groups of subjects. A significant increase in GH levels after sumatriptan was observed in controls but not in acromegalics. An age-related negative trend in GH response to sumatriptan was observed in controls.
Conclusions: Our study indicated that 5-HT1D receptors are not involved in PRL and GH secretion in middle-aged acromegalics.