Inhibition of Hypoglycemia-Induced Growth Hormone Secretion by the Serotonin Antagonists Cyproheptadine and Methysergide

Growth hormone secretion is provoked by hypoglycemia. Since hypothalamic serotonin content increases during insulin-induced hypoglycemia, the role of hypothalamic serotonin in growth hormone secretion in man was examined. Hypoglycemia-induced growth hormone release in normal volunteers was studied during a control period and after two days of administration of serotonin antagonists, cyproheptadine and methysergide. Plasma growth hormone was measured by radioimmunoassay, and total growth hormone secretion was expressed as the area under the growth hormone curve from 0 to 120 minutes. Cyproheptadine administration resulted in a 59 per cent reduction (p<0.01), and methysergide in a 35 per cent reduction (p<0.05) in growth hormone secretion. The decrease in plasma glucose during the control and treatment periods indicated a comparable stimulus for growth hormone release in both study groups. If these drugs act by antagonizing serotonin, as assumed, this study suggests that serotonin is involved in hypoglycemia-induced growth hormone release. (N Engl J Med 289:236–239, 1973).