Hypoglycemia in the nondiabetic patient

Under most physiologic conditions encountered in modern life, glucose is the brain's obligate fuel (Cryer, 117:868-870, 2007); therefore maintenance of blood glucose within the physiological range is of great importance. Hypoglycemic disorders, although uncommon (Service, J Clin Invest 332:1144-1152, 1995), are significant because low blood glucose leads to symptoms and signs of brain dysfunction. Profound or prolonged hypoglycemia may lead to cardiac arrhythmias, cognitive dysfunction or brain death (Cryer, N Eng J Med 117:868-870, 2007). However, the symptoms of hypoglycemia such as tachycardia, sweating, tremor, and nervousness are not specific to hypoglycemia. To diagnose a hypoglycemic disorder, it is necessary to document low blood glucose at the time of symptoms compatible with neuroglycopenia. These symptoms should be ameliorated by correction of the hypoglycemia. This is often referred to as Whipple's triad (Whipple, Can Med Assoc J 66:334-342, 1952) and such documentation must underpin the diagnosis of a hypoglycemic disorder. In this chapter, we discuss the important aspects of hypoglycemic disorders, including clinical presentation, differential diagnosis, evaluation, and treatment.