5104 Ectopic Insulinoma- a Rare Presentation of a Rare Tumor

Abstract Disclosure: O. Lavrynenko: None. A. DeMarsilis: None. C. Jiang: None. R. Middelbeek: None. H. Rosen: None. M.E. Patti: None. Background. Insulinoma is a rare, functioning neuroendocrine tumor (NET) typically localized within the pancreas, that secretes insulin, resulting in hypoglycemia. Ectopic insulinoma is even more rare than pancreatic insulinoma and is more difficult to diagnose. Case report. This 31-year-old previously healthy woman, who had an uncomplicated pregnancy and a healthy baby in October 2021, presented with intermittent hypoglycemia for more than 8 months. She denied any prior use of insulin or antidiabetic medications and was not currently taking any medications at all. There is no history of bariatric or other GI surgery. While nursing her baby in early 2022, she was noted to have a capillary blood glucose (BG) between 20-30 mg/dl, and reported both adrenergic and neuroglycopenic symptoms of hypoglycemia; these usually occurred in the morning or before lunch, especially if lunch was delayed. She wore a Libre CGM which revealed episodic hypoglycemia, which correlated with her timeline of symptoms. She reported weight gain of 8 lbs during this period. Laboratory data obtained after a 10-12 hour fast revealed hypoglycemia (venous glucose 39 mg/dL) with inappropriately high plasma insulin (42.3 mIU/ml), C- peptide (3.78 ng/ml), and proinsulin (99 pmol/L). Beta-hydroxybutyrate was 0.05 mmol/L (reference