Changes in plasma insulin during ethanol-induced hypoglycemia

Abstract

Intravenous ethanol infusions following a 36-hr fast have been carried out on nonobese and obese nondiabetic subjects, a group of nonobese mild diabetic patients, and two patients with suspected insulinomas. After a 36-hr fast, ethanol induces moderate hypoglycemia, which was, in normal subjects, associated with a fall in plasma insulin to values of < 1 μU/ml. Expressed in relation to the plasma glucose, the plasma insulin levels decreased by a mean of 65% for a 10 mg 100 ml fall in the plasma glucose. Plasma insulin levels in obese subjects fell markedly during the hypoglycemia, the per cent fall relative to the fall in plasma glucose being similar to that in normal subjects. Nonobese, mildly diabetic subjects had an absolute fall in insulin levels similar to that in normal subjects, but when expressed in terms of the initial insulin levels and the fall in plasma glucose, they had significantly decreased suppression of insulin levels with a mean fall of 29%/10 mg/100 ml fall in plasma glucose. Two normal subjects with α-adrenergic blockade had little suppression of plasma insulin levels in response to hypoglycemia. Both patients with suspected insulinomas had markedly diminished suppression of plasma insulin levels during ethanol-induced hypoglycemia, and erratic variation in plasma insulin concentrations, which were not associated with changes in plasma glucose concentration. An ethanol infusion is useful in excluding a suspected insulinoma, and may be useful in establishing the diagnosis in patients in whom the diagnosis is in doubt.