SAT-549 A Case of Renal Failure Mimicking Insulinoma

Abstract Disclosure: A. Thatte: None. T. McLaughlin: Eli Lilly & Company, Recordati, Vogenyx, Weight Watchers, January AI, Amylyx. M. Tan: Novo Nordisk, Eiger Biopharmaceuticals, Amylyx. Introduction: Hypoglycemia is common in patients with end-stage renal disease (ESRD). Multiple mechanisms are involved including reduced clearance of insulin, impaired renal glucogenesis and suboptimal nutritional status. Differentiating between insulinoma and ESRD as the cause of hypoglycemia is challenging given decreased clearance of insulin, c-peptide, and proinsulin. We present a case of severe hypoglycemia in a patient with ESRD. Clinical Case: The patient was a 53-year-old male with ESRD from autosomal dominant polycystic kidney disease on hemodialysis with recurrent hypoglycemia for two years duration. The episodes generally occurred overnight or 1-2 hours after eating. Fingerstick glucose measurements were in the range of 40-50 mg/dL with symptoms of anxiety, sweating, nausea and dizziness, relieved by consuming glucose. He had no history of liver or adrenal dysfunction or use of hypoglycemia-inducing medications. He was admitted for a 72-hour fast. Within four hours, fingerstick glucose reached 52 mg/dL. Blood sample was drawn showing a plasma glucose of 55 mg/dL (n 70-100 mg/dL), insulin level 18uU/mL (n <20 uU/mL), C-peptide level 8.6 ng/mL (n 0.8-4.0 ng/mL), proinsulin 46 pmol/L (n 3-20 pmol/L), beta-hydroxybutyrate <0.1 mmol/L (n 0.2-2.8 mmol/L), negative sulfonylurea screen. Cortisol during admission ranged from 18-35 ug/dL (n 4-24 ug/dL), ACTH 18-40 pg/mL (n 10-60 pg/mL). Insulin-autoantibody was <0.4 U/mL (n <0.4 U/mL) and IGF-2 was 562 ng/mL (n 288-736 ng/mL). TSH was 0.97 uIU/ml (n 0.40-4.0 uIU/mL) and free thyroxine 1.1 ng/dL (n 0.6-1.6 ng/dL). He underwent imaging studies with MRI and CT scan which did not show any pancreatic lesion. He also underwent endoscopic ultrasound with fine needle aspiration of a visualized 3 cm lesion which showed only lymphoid tissue. Given daily hypoglycemia, treatment was started with octreotide subcutaneous injection 30 mg long-acting release every two weeks with some improvement. Due to breakthrough episodes of hypoglycemia, diazoxide 75 mg three times daily was added which reduced frequency and severity of episodes. He was encouraged to eat small frequent meals and have peanut butter before bedtime. Ga-68 dotatate PET scan was ordered, however in the interim the patient underwent kidney transplant and hypoglycemia resolved. Years later, he was admitted with an acute kidney injury (AKI) and recurrence of hypoglycemia. C-peptide was 13.70 (n 1.10-4.40) ng/mL with glucose of 95 mg/dL. Hypoglycemia again resolved with improvement in renal function. Conclusion: This case demonstrates how in renal failure, hypoglycemia from decreased clearance of insulin can be difficult to distinguish from insulinoma. The diagnosis was made clear when hypoglycemia resolved after transplant and reoccurred with AKI. Medical management with diazoxide and somatostatin analog improved severity and frequency of symptoms until transplant. Presentation: Saturday, July 12, 2025