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

• Published in: American journal of physiology: endocrinology and metabolism 1999-08, Vol.277 (2), p.E253-E258
• Main Authors: Jaffe, Craig A, Huffman, Bryan W, Demott-Friberg, Roberta
• Format: Article
• Language: English
• ISSN: 0193-1849; 1522-1555
• DOI: 10.1152/ajpendo.1999.277.2.e253

Division of Endocrinology and Metabolism, Department of Internal Medicine, University of Michigan Medical Center and Ann Arbor Veterans Affairs Medical Center, Ann Arbor, Michigan 48109-0354 Although insulin-induced hypoglycemia is a potent stimulus for growth hormone (GH) secretion in humans, hypoglycemia was reported to suppress GH in sheep. We investigated whether GH suppression in sheep during insulin hypoglycemia resulted from the dose of insulin administered or the fed state of the animal. Saline or insulin (0.05, 0.2, 1.0, or 5.0 U/kg) intravenous boluses were administered to eight fasted ewes in a crossover experiment. In another 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 comparable hypoglycemia, although the duration of hypoglycemia increased directly 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 identical degree of hypoglycemia but no increase in GH. Insulin-hypoglycemia stimulates GH secretion in sheep in a manner similar to humans, and the response is dependent on both fed state and insulin dose. hypothalamus; pituitary; neuroendocrine; somatostatin; glucose