A Case of Factitious Hypoglycemia Induced by Self-Administration of Sulfonylurea

Abstract

A 23-year-old nurse had sulfonylurea-induced factitious hypoglycemia. She demonstrated the high plasma insulin level relative to blood glucose and the positive prolonged fasting test. The response of plasma insulin to glucagon and tolbutamide was not typical of insulinoma. Furthermore, plasma C-peptide concentration was suppressed following the injection of insulin. These findings, together with no demonstrable radiologic evidence of an insulin secreting tumor prompted us to measure the serum concentration of sulfonylurea though she adamantly denied taking hypoglycemic drug. The presence of a significant amount of sulfonylurea, 13.3mg/dl equivalent to tolbutamide, in her serum assured our suspicion of factitious hypoglycemia. The differential diagnosis between insulinoma and other causes of hypoglycemia is discussed, specially emphasizing the suppressability of plasma C-peptide concentration following the injection of insulin for ruling out the former.