HYPOTHALAMIC-PITUITARY ACTIVATION DOES NOT DIFFER DURING HUMAN AND PORCINE INSULIN-INDUCED HYPOGLYCEMIA IN INSULIN-DEPENDENT DIABETES-MELLITUS

Although pituitary hormones play only a minor role in acute hormonal c ounterregulation during insulin-induced hypoglycemia, their concomitan t secretion with the profound sympathoadrenal response provides an ind icator of hypothalamic-pituitary activation. The release of different amounts of beta-endorphin, growth hormone, and adrenocorticotropin dur ing human (HI) and porcine (PI) insulin-induced hypoglycemia would ser ve as a pointer to a different insulin species effect on hypothalamic- pituitary response. We performed a controlled, double-blind study with randomization to either HI or PI to compare insulin effects during de veloping and established hypoglycemia. The glucose clamp technique was used to lower the blood glucose concentration stepwise (3.3, 2.2, 1.7 mmol/l) over similar periods in ten patients with insulin-dependent d iabetes mellitus. P-endorphin, growth hormone, and adrenocorticotropin levels were determined by radioimmunoassay from arterialized blood at the above plateaus. A different action of HI or PI on peripheral gluc ose metabolism was not found. Pituitary hormones increased significant ly during hypoglycemia (analysis of variance for hypoglycemic effects: beta-endorphin, P<0.02; growth hormone, P<0.04; adrenocorticotropin, P<0.05). No insulin species effect was detected. Hypothalamic-pituitar y activation during insulin-induced hypoglycemia is independent of the insulin species used, which supports earlier observations of an ident ical sympathoadrenal response during HI- and PI-induced hypoglycemia.