Acute suppressive effect of human growth hormone on insulin release induced by glucagon and tolbutamide in man.

The acute effect of human growth hormone on glucagon--and tolbutamide--induced insulin release was investigated in 14 non-obese subjects with normal glucose tolerance. Sixty mn after an i.v. growth hormone infusion of 40 mug/kg per kg body weight, the insulin response to glucagon (10 subjects) as well as to tolbutamide (6 subjects) was significantly suppressed by about 35%, both if the insulin secretion was expressed as change in peak response (p less than 0.05 for both insulinogogues) or as per cent change of the integrated insulin area over 30 minutes (p less than 0.005 and p less than 0.05, respectively). A lesser reduction of glucagon-induced insulin secretion was observed also after smaller doses of growth hormone (10 and 20 mug/kg). The reduction of the insulin response was associated with a significantly smaller blood glucose fall following the glucagon and tolbutamide administration. These results support the hypothesis that growth hormone in vivo has an acute suppressive effect on insulin secretion, and show that this action is not limited to glucose-induced stimulation of the islets.