HYPOGLYCEMIA: INTRODUCTION

Hypoglycemia is most commonly caused by drugs used to treat diabetes mellitus or by exposure to other drugs, including alcohol. However, a number of other disorders, including insulinoma, critical organ failure, sepsis and inanition, hormone deficiencies, non-β-cell tumors, inherited metabolic disorders, and prior gastric surgery, may cause hypoglycemia (Table 339-1). Hypoglycemia is most convincingly documented by Whipple’s triad : (1) symptoms consistent with hypoglycemia, (2) a low plasma glucose concentration measured with a precise method (not a glucose monitor), and (3) relief of those symptoms after the plasma glucose level is raised. The lower limit of the fasting plasma glucose concentration is normally approximately 70 mg/dL (3.9 mmol/L), but substantially lower venous glucose levels occur normally, late after a meal. Glucose levels <55 mg/dL (3.0 mmol/L) with symptoms that are relieved promptly after the glucose level is raised document hypoglycemia. Hypoglycemia can cause serious morbidity; if severe and prolonged, it can be fatal. It should be considered in any patient with episodes of confusion, an altered level of consciousness, or a seizure.

Table 339-1 Causes of Hypoglycemia

Fasting (Postabsorptive) Hypoglycemia

Drugs Especially insulin, sulfonylureas, ethanol Sometimes quinine, pentamidine Rarely salicylates, sulfonamides, others Critical illnesses Hepatic, renal, or cardiac failure Sepsis Inanition Hormone deficiencies Cortisol, growth hormone, or both Glucagon and epinephrine (in insulin-deficient diabetes) Non-β-cell tumors Endogenous hyperinsulinism Insulinoma Other β cell disorders Insulin secretagogue (sulfonylurea, other) Autoimmune (autoantibodies to insulin or the insulin receptor) Ectopic insulin secretion Disorders of infancy or childhood Transient intolerance of fasting Congenital hyperinsulinism Inherited enzyme deficiencies

Reactive (Postprandial) Hypoglycemia

Alimentary (postgastrectomy) Noninsulinoma pancreatogenous hypoglycemia syndrome In the absence of prior surgery Following Roux-en-Y-gastric bypass Other causes of endogenous hyperinsulinism Hereditary fructose intolerance, galactosemia Idiopathic

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