A 30-year-old nursing student presents with confusion, sweating, hunger, and fatigue. Blood sugar is 40 mg/dL. The patient has no history of diabetes mellitus, although her sister is an insulin-dependent diabetic. The patient has had several similar episodes over the past year, all occurring just prior to reporting for work in the early morning. At the time of hypoglycemia, the patient is found to have a high insulin level and a low C peptide level. Which of the following is the most likely diagnosis?
A. Reactive hypoglycemiaThis clinical picture and laboratory results suggest factitious hypoglycemia caused by self-administration of insulin. The diagnosis should be suspected in healthcare workers, patients or family members with diabetes, and others who have a history of malingering. Patients present with symptoms of hypoglycemia and low plasma glucose levels. Insulin levels will be high, but C peptide will be undetectable. Endogenous hyperinsulinism, such as would be seen with an insulinoma, would result in elevated plasma insulin concentrations (> 36 pmol/L) and elevated C peptide levels (> 0.2 mmol/L). C peptide is derived from the breakdown of proinsulin, which is produced endogenously; thus C peptide will not rise in the patient who develops hypoglycemia from exogenous insulin. Reactive hypoglycemia occurs after meals and is self-limited. A rapid postprandial rise in glucose may induce a brisk insulin response that causes transient hypoglycemia hours later. It may be associated with gastric or intestinal surgery. Pheochromocytoma causes hyperglycemia due to the insulin counter-regulatory effect of catecholamines. Sulfonylurea, an insulin secretagogue, would increase natural insulin secretion, resulting in elevated insulin and elevated C peptide levels.