Today we went over a classic case of hypoglycemia from an insulinoma. Here’s the NEJM case learning points.
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- Patients with hypoglycemia present with neuroglycopenic symptoms (e.g., confusion, fatigue, focal neurologic deficits, and seizures) and autonomic symptoms (e.g., palpitations, tremors, anxiety, diaphoresis, and hunger).
- The diagnosis of hypoglycemia requires fulfillment of Whipple’s triad: symptoms compatible with hypoglycemia, laboratory-confirmed hypoglycemia, and relief of symptoms after the administration of glucose.
- Hypoglycemia is usually seen as an iatrogenic complication of diabetic therapy. Other causes include factitious hypoglycemia (a result of surreptitious use of insulin or sulfonylureas), liver failure, sepsis, insulinoma, nesidioblastosis, hypoglycemia caused by insulin autoimmunity, and the secretion of IGF-2 by a tumor.
- Insulinoma is the most likely cause of hypoglycemia in a patient who fulfills the criteria for detectability of insulin and C-peptide during a hypoglycemic episode but is otherwise well. More than 95% of insulinomas are located in the pancreas. Useful initial imaging studies include abdominal CT and MRI. Endoscopic pancreatic ultrasonography is a more sensitive test but is also more invasive. Intraarterial calcium stimulation with hepatic venous sampling for insulin levels may also help to localize insulinomas or diagnose nesidioblastosis.
- Insulinomas are associated with MEN-1 in 5 to 10% of cases; these patients will almost always have evidence of hyperparathyroidism.
- Medical treatment of insulinomas includes diazoxide and high glucose intake; definitive therapy is surgical excision.
