Insulinoma Misdiagnosed as Factitious Hypoglycemia

Hypoglycemia is an important cause of referral to endocrinologists. We report a case of 34-year-old female presenting with Whipple's triad. The blood test documented hyperinsulinemic hypoglycemia and the presence of glibenclamide. Blood tests were repeated, confirming the results. Considering these laboratory findings, factitious hypoglycemia was suspected and the patient was referred to a psychiatry clinic. However, following further investigation, a pancreatic neuroendocrine tumor was diagnosed and submitted to surgical resection. At this point two highly unlikely scenarios remained: either the patient had a simultaneous diagnosis of a neuroendocrine tumor and factitious hypoglycemia or the glibenclamide result was a false positive due to a serum interference. In order to clarify the situation further investigation was performed and the interference hypothesis was confirmed. This case shows that a diagnosis of factitious hypoglycemia should not be categorically assumed, even when in the presence of a positive measurement of secretagogues in blood tests.