The most common cause of hyperinsulinemic hypoglycemia is reported to be insulinoma.10 In case 1, the fasting glucose level was 15 mg/dL, and the insulin level was elevated (15 μU/mL); in case 3, hypoglycemia (29 mg/dL) was detected when the patient was admitted to the hospital because of a disturbance of consciousness. Here, INS is linked to pancreatic insulinoma.