Insulinoma Presenting with Reactive Hypoglycemia: Evaluating the Effect of Tumor Resection via Continuous Glucose Monitoring

Abstract

A 71-year-old woman previously diagnosed with reactive hypoglycemia was transferred to our emergency unit because of loss of consciousness. Her plasma glucose level was 27 mg/dL, and continuous glucose monitoring (CGM) revealed postprandial asymptomatic hypoglycemia. A hypervascular tumor was identified via computed tomography in the distal pancreas, and the diagnosis of insulinoma was confirmed using the selective arterial calcium stimulation test. Although no episodes of hypoglycemia were observed during CGM after resection, a pathological examination identified regional lymph node metastasis. It is important to consider insulinoma as a cause of postprandial hypoglycemia, and CGM is useful for evaluating treatment outcomes.

Keywords: continuous glucose monitoring; insulinoma; metastasis; postprandial hypoglycemia.

Figure 1.

Contrast-enhanced computed tomography image of the abdomen. The arrowhead indicates a hypervascular tumor with a diameter of 18 mm.

Figure 2.

Insulin secretion responses after selective arterial calcium stimulation. RHA: right hepatic artery, CA: celiac artery, SA: splenic artery, GDA: gastroduodenal artery, PHA: proper hepatic artery, SMA: superior mesenteric artery

Figure 3.

A pathological examination of the pancreatic tumor. A) Resected pancreatic tumor measuring 25.0×23.0×13.0 mm, B) immunostaining for insulin, C) immunostaining for chromogranin A.

Figure 4.

Continuous glucose monitoring before (A) and after (B) laparoscopic resection of the distal pancreatic tumor. A black arrow indicates a rapid decline in the blood glucose after excessive glucose infusion.