Insulin hypoglycemia and growth hormone secretion in sheep: a paradox revisited

Although insulin-induced hypoglycemia is a potent stimulus for growth hormo ne (GH) secretion in humans, hypoglycemia was reported to suppress GH in sh eep. We investigated whether GH suppression in sheep during insulin hypogly cemia resulted from the dose of insulin administered or the fed state of th e animal. Saline or insulin (0.05, 0.2, 1.0, or 5.0 U/kg) intravenous bolus es were administered to eight fasted ewes in a crossover experiment. In ano ther experiment, four sheep were fed 2 h before intravenous administrations of either 0.2 or 5 U/kg of insulin. All doses of insulin resulted in compa rable hypoglycemia, although the duration of hypoglycemia increased directl y with insulin dose. Hypoglycemia in fasted animals stimulated GH secretion . The GH rise above baseline was inversely related to the insulin dose, and the insulin doses of 1 and 5 U/kg resulted in late suppression of GH below baseline concentrations. Insulin administration to fed animals caused an i dentical degree of hypoglycemia but no increase in GH. Insulin-hypoglycemia stimulates GH secretion in sheep in a manner similar to humans, and the re sponse is dependent on both fed state and insulin dose.