Insulin-Like and Diabetogenic Effects of Growth Hormone in Healthy Subjects, Diabetics, and Low Insulin Responders*

The effect of two doses of GH (10 and 40 µg/kg) on glucose homeostasis and insulin secretion was studied in 10 high insulin responders, 10 low insulin responders, and 6 subjects with chemical diabetes. GH was given as an iv infusion over 30min and, after a lag period of 60 min, a standard glucose infusion test (GIT) was performed. The insulin-like effect of GH was demonstrated in all groups under basal conditions but was more prominent in the diabetic than in the high and low insulin responders; it was evident even during the first 30 min of the GIT in the diabetics and low responders but not in the high responders. The insulin-like action of GH shifted to an antiinsulin one rather abruptly and was evident 30 min after discontinuation of the GIT. Hence, the GH-mediated decrease in the glucose disappearance rate, as seen after withdrawal of the GIT, wasof the same magnitude in all groups. The high GH dose seemed to have a more pronounced hypoglycemic effect than the low one, but the difference was not significant. As to the diabetogenic effect, there was no difference between the two GH doses. Both significantly suppressed basal insulin levels in all groups, and glucose stimulated insulin release in the diabetics and low insulin responders. In high insulin responders, the latter effect wasevident only in the presence of the high dose of the hormone, indicating that the diabetogenic effect is predominantly mediated by the peripheral effects of GH and not by the suppression of insulin release. In conclusion, it has been demonstrated that the insulin-like effect of GH as well as its inhibitory effect on insulin release were more pronounced in diabetic subjects and low insulin responders, whereas the diabetogenic effect seemed to be of the same magnitude in these two groups as well as in the high insulin responders. (J Clin EndocrinolMetab49: 456, 1979)