A rare case of insulinoma presenting with postprandial hypoglycemia.

backgroundAlthough fasting hypoglycemia has historically been considered the hallmark of insulinoma, postprandial hypoglycemia has also been occasionally reported as the predominant feature. We report a rare case of an insulinoma diagnosed in an individual presenting exclusively with postprandial hypoglycemia without fasting hypoglycemia. CASE REPORT: A 47-year-old woman with medical history of migraine, depression, hypercholesterolemia, iron deficiency anemia, and peptic ulcer disease presented with complaints of frequent episodes of dizziness, blurring of vision, and anxiety over the past 4 months. These episodes usually occurred 1-2 hours after eating and resolved with ingestion of sugary foods. Home glucometer readings during typical symptoms were 47-64 mg/dL. Physical exam revealed a healthy-appearing middle-aged female with BMI of 28. Laboratory data after an overnight fast showed serum blood glucose 77 mg/dL and AM cortisol 9.6 (5-25 µg/dl). Hemoglobin A1C, thyroid function tests, IGF-1, liver function tests, and kidney function were in normal range. She was instructed to bring a typical meal to the clinic for monitoring of postprandial glucose levels. Three hours after ingestion of the meal, she developed typical adrenergic symptoms during which laboratory analysis revealed a serum glucose level of 44 mg/dL, C-peptide of 2.9 (0.8-3.1 ng/ml), insulin level of 32 (0-17 µIU/lt), negative sulfonylurea screen, and insulin antibodies. She was treated with 15 grams of oral glucose, which alleviated her symptoms. Medical therapy with acarbose was attempted, but did not lead to significant reduction in hypoglycemic events. CT abdomen/pelvis confirmed the presence of a tumor in the tail of the pancreas. The patient subsequently underwent partial pancreatectomy, splenectomy, and lymph node resection, with resolution of symptoms. Histopathological analysis confirmed insulinoma.

conclusionsWe present a rare case of an insulinoma in the setting of verified postprandial hypoglycemia with elevated insulin and C-peptide levels. Although insulinomas typically present with fasting hypoglycemia, it is important to consider insulinoma in the differential diagnosis of patients presenting exclusively with postprandial hypoglycemia.