Case Presentation: An 80-year-old female with dementia presented with 4 months of intermittent confusion, hypoglycemia, and associated generalized weakness. Her symptoms resolved with eating. She had no diabetic medications at home. She was hospitalized 1 month prior for these symptoms; her blood glucose during that admission was 39 mg/dL, C-peptide was 6.9 ng/mL (reference range [RR] 1.1 – 4.4 ng/mL), and insulin level was 48 uIU/mL (RR 2.6 – 24.9 uIU/mL). An abdominal MRI was unremarkable. Her hypoglycemia was thought to be from recent poor oral intake and she was discharged. On this presentation, vitals were normal. She was oriented only to identity and she had disorganized thinking. Her blood glucose was 44 mg/dL (RR 70-100 mg/dL). Emergent intravenous (IV) dextrose resulted in normalization of hypoglycemia (71 mg/dL) and confusion. She was admitted to the hospital, during which she had repeat rapid declines in blood glucose when continuous IV dextrose was stopped. With hypoglycemia, she had recurrence of confusion that resolved with IV dextrose. She underwent a prolonged fast and, while hypoglycemic (38 mg/dL), C-peptide was 965 pmol/L (RR < 200 pmol/L), insulin level 29 mU/L (RR < 3 mU/L). Sulfonylurea screen was negative. Abdominal CT revealed a 1.1 cm hyperattenuating lesion in pancreatic uncinate process. Follow-up PET CT showed a hypermetabolic 1.7 cm mass in the pancreatic uncinate process, consistent an insulinoma (Figure 1). Treatment options included pancreaticoduodenectomy versus medical management. After discussion with surgery and palliative care, medical management was pursued. She was started on diazoxide and maintained euglycemia without return of symptoms thereafter. She was discharged home and ultimately pursued hospice care for the insulinoma and her dementia.
Discussion: Insulinoma is a rare diagnosis (1-2 per million people), representing 1-2% of all pancreatic neoplasms.1 They are most common in the fifth and sixth decades of life with a female predominance.2 Insulinomas are tumors of the pancreas that intermittently secrete insulin, causing hypoglycemia. Identification of Whipple’s triad is key to the diagnosis of insulinoma. Whipple’s triad consists of 1) plasma glucose < 50 mg/dL; 2) concomitant symptoms of hypoglycemia (e.g., confusion, weakness, etc.); and 3) rapid symptom improvement with glucose administration.3 Elevated serum insulin and C-peptide levels measures during a hypoglycemic episode supports the diagnosis. Surgery remains the gold standard for treatment. Prior to surgery, localization of the tumor by CT scan or MRI is paramount. For patients where surgery is not successful or is not pursued, medical management with octreotide or diazoxide is an option. Octreotide is a somatostatin analog that inhibits insulin secretion.1 Diazoxide inhibits insulin secretion from pancreatic beta cells and increases hepatic glucose production.4
Conclusions: Hospitalists should maintain a high level of suspicion for insulinoma in patients presenting with hypoglycemia. Presence of Whipple’s triad and consistent labs obtained during a hypoglycemia help confirm the diagnosis. CT and MRI are useful for localization of an insulinoma, which is important for surgical planning. If surgery is not an option or not desired, medical management is possible.
