Introduction: Insulinomas are rare neuroendocrine tumors that are typically < 2.0cm, benign, sporadic tumors. The diagnosis is often delayed or missed due to insulinoma rarity and vague symptoms. We present a patient with insulinoma initially presenting for seizure-related motor vehicle accident.
Case Description: A 37-year-old woman with a medical history of gestational diabetes was hospitalized after a motor vehicle accident likely due to hypoglycemic seizure, with initial glucose of 32 mg/dL. During her hospitalization, the patient had consistent episodes of fasting and postprandial hypoglycemia of 32-70 that became symptomatic below 50, accompanied by Whipple’s triad, requiring continuous dextrose 10% infusions. She denied any pre-existing glycopenic symptoms and was not taking any medications at home. Insulin autoantibodies, sulfonylurea screen tests, and thyroid labs were unremarkable. A 72-hr fasting test was initiated to rule out endogenous causes of insulin overproduction. Her labs for a venous glucose level of 46mg/dL showed significant elevation in C peptide and insulin with suppressed beta hydroxybutyrate, all meeting diagnostic criteria for insulinoma. Abdominal magnetic resonance imaging (MRI) revealed a 1.3cm mass in the pancreatic tail. The patient underwent laparoscopic distal pancreatectomy and pathologic evaluation of the tumor was consistent with a well-differentiated neuroendocrine tumor. She had no biochemical evidence of parathyroid or pituitary disease and genetic testing for MEN1 was negative. The patient tolerated the surgery well with no recurrence of hypoglycemia.
Discussion: Insulinomas are a rare cause of recurrent hypoglycemia in non-diabetic patients, occurring in 1- 4 people per million a year. They present more commonly in patients that are middle aged, female, and with a higher BMI. Diagnosis is achieved by satisfying the criteria of Whipple’s triad, hypoglycemia (plasma glucose < 50 mg/dL), neuroglycopenic symptoms, and prompt relief of symptoms following the administration of glucose. The gold standard is performing a 72-hour fast. Most masses are first identified by CT or MRI. According to a 60-year longitudinal study, most patients with insulinoma reported neuroglycopenic symptoms within nearly 1.5 years preceding the diagnosis. In the preoperative period and in patients with unresectable or metastatic tumors, medical management with diazoxide and octreotide can be considered for recurrent hypoglycemia. Our case highlights how a targeted approach to evaluating non-diabetic patients with whipple triad positive hypoglycemia can help detect this rare entity early on.