SAT-074 - Recurrent Hypoglycemia Due to Insulinoma: Undiagnosed for 17 Years Despite Prior Evaluation

Background:
Insulinoma is a rare pancreatic neuroendocrine tumor typically diagnosed early due to symptomatic hypoglycemia; however, delayed diagnosis may occur when prior evaluations are unrevealing.

Case Presentation:
A man in his 50s with hypertension presented with recurrent hypoglycemic symptoms beginning 17 years ago, characterized by diaphoresis and confusion, with prior hospitalizations. Twelve years ago, he underwent evaluation for hypoglycemia, which was unrevealing, with plasma glucose remaining above 4.4 mmol/L (>80 mg/dL) during testing.

Over the year prior to presentation, symptoms increased in frequency, necessitating frequent carbohydrate intake. Episodes were characterized by diaphoresis and confusion when untreated, lasting up to 30 minutes. Capillary glucose measurements were intermittently as low as 1.4–2.3 mmol/L (25–41 mg/dL). He denied recent loss of consciousness or gastrointestinal symptoms. His weight remained stable, and he exercised daily.

He was admitted for a supervised 72-hour fast. Plasma glucose decreased to 1.4 mmol/L (26 mg/dL), at which point the fast was aborted. Concurrent laboratory evaluation demonstrated inappropriately elevated insulin 157.6 pmol/L (22.7 µIU/mL), C-peptide 1.7 nmol/L (5.0 ng/mL), and proinsulin 10.6 pmol/L, with suppressed beta-hydroxybutyrate 0.17 mmol/L. HbA1c was 4.8%. Insulin antibodies and sulfonylurea screen were negative, confirming endogenous hyperinsulinemic hypoglycemia.

CT imaging identified a 2.9 cm arterially enhancing pancreatic head mass abutting but not encasing the superior mesenteric vein, consistent with a pancreatic neuroendocrine tumor. He was initiated on octreotide (50 mcg three times daily), subsequently increased to 75 mcg three times daily, with partial reduction in hypoglycemia while awaiting surgery. He subsequently underwent pancreaticoduodenectomy with complete resolution of symptoms.

Conclusion:
This case highlights that insulinoma may remain undiagnosed for years despite recurrent hypoglycemia and prior negative evaluations. Persistent or progressive symptoms should prompt repeat biochemical assessment and localization, as timely surgical intervention is curative.

*Unless otherwise noted, all abstracts presented at ENDO must not be released to the press or the public until the date and time of presentation. For oral presentations, the abstracts are embargoed until the session begins. The Endocrine Society reserves the right to lift the embargo on specific abstracts that are selected for promotion prior to or during ENDO.*