Regulation of carbohydrate metabolism and response to hypoglycemia.

Postabsorptive and postprandial glucose concentrations are regulated by the interaction of insulin and the counterinsulin hormones. Either an excess of insulin or insulin-like activity or a deficiency of counterregulatory hormone secretion can cause hypoglycemia. Impairment of glycogen storage or breakdown is likely to lead to a relatively rapid fall in glucose, whereas hypoglycemia caused by alterations in gluconeogenesis are generally observed with a more prolonged fast. Although glucagon, epinephrine, cortisol, and growth hormone all possess biologic activity capable of opposing insulin action, glucagon appears to be the primary hormone responsible for defense against hypoglycemia. In the absence of glucagon, epinephrine becomes important. Cortisol and growth hormone appear to serve a permissive role during recovery from acute hypoglycemia. Whether they have a more important role during recovery from chronic hypoglycemia remains to be determined.