[Hypoglycemia--occurrence, causes and hormonal counterregulatory mechanisms in healthy persons and in patients with IDDM]

The occurrence of hypoglycemia is common in patients with insulin-dependent diabetes mellitus. They experience an average of one to two episodes of symptomatic hypoglycemia per week; 10-20% suffer at least one episode of severe hypoglycemia in a given year. The incidence of severe hypoglycemia in diabetic patients treated with intensive insulin therapy is threefold higher than in patients on conventional insulin therapy and 55% of all episodes occurred in sleep. Prevention of hypoglycemia or the restoring of euglycemia involve the dissipation of metabolic insulin effects and activation of counterregulatory hormone responses (glucagon, catecholamines, growth hormone, cortisol). Among counterregulatory mechanisms there exists hierarchy. The glycemic threshold for release of glucoregulatory hormones in normal people is about 3.8 mmol/l. The glucose counterregulatory system is often impaired in patients with diabetes mellitus with the onset early after diagnosis of diabetes mellitus. Impaired glucagon response is almost universally present after 5 years of diabetes. The defect is selective and the mechanism is not fully explained. Most often it is considered a defect in signal perception of alfa-cells, a rearrangement of islets of Langerhans with predominance of delta-cells or mechanism of central adaptation. After 5-10 years of diabetes glucose counterregulation becomes further impaired with a defect in epinephrine secretion. A possible mechanism is the abnormality at the CNS level. Autonomic neuropathy is a contributory factor. Defective hormonal counterregulation correlates well with duration of diabetes and strict glycemic control. If the glucagon response is intact the hormonal counterregulation is sufficient even in the presence of the impairment of other glucoregulatory factors.(ABSTRACT TRUNCATED AT 250 WORDS)