Hyperinsulinism results from overproduction of insulin by the pancreatic islets. Symptoms resemble those of excessive doses of insulin and are attributable to the same mechanism, an abnor-mal reduction in blood glucose levels. Clinically, it is character-ized by episodes during which the patient experiences unusual hunger, nervousness, sweating, headache, and faintness; in severe cases, seizures and episodes of unconsciousness may occur. The findings at the time of surgery or at autopsy may indicate hyper-plasia (overgrowth) of the islets of Langerhans or a benign or malignant tumor involving the islets and capable of producing large amounts of insulin (see preceding discussion). Occasion-ally, tumors of nonpancreatic origin produce an insulin-like material that can cause severe hypoglycemia that may be re-sponsible for seizures coinciding with blood glucose levels too low to sustain normal brain function (ie, below 30 mg/dL [1.6 mmol/L]).
All the symptoms that accompany spontaneous hypoglycemia are relieved by the oral or parenteral administration of glucose. Surgical removal of the hyperplastic or neoplastic tissue from the pancreas is the only successful method of treatment. About 15% of patients with spontaneous or functional hypoglycemia even-tually develop diabetes mellitus.