Case Study: Diagnosis of Insulinoma Using Continuous Glucose Monitoring System in a Patient With Diabetes

K.D., a 20-year-old white female college student was brought by her parents for evaluation of hypoglycemia. She had experienced multiple episodes of palpitations, blurred vision, and left facial paresthesias for a year, progressively worsening and occurring more frequently in the 2 months just before her appointment. Usually the episodes occurred between 3:00 and 7:30 p.m. The symptoms occurred without regard to meals and were relieved with food or juice. Her most severe witnessed episode, which occurred while she was at college, happened a few days before the consultation, while K.D. was working, 2 hours postprandially. Observers reported that she appeared confused, agitated, and diaphoretic. Her glucose via fingerstick by paramedics was 35 mg/dl. She received intravenous dextrose, and subsequently her glucose rose to 217 mg/dl with resolution of her symptoms. She had several episodes with neuroglycopenic symptoms and glucose levels of 35-45 mg/dl. There was no history indicating diabetic medications in her home. She also complained of a 25-lb weight gain during the past year. A year before her visit, K.D. was diagnosed with diabetes by oral glucose tolerance test (OGTT). The results were: View this table: At that time, she had a normal hemoglobin A1c, and she was instructed in diet and exercise. No antidiabetic medications had been prescribed. K.D. had a psychiatric evaluation, was diagnosed with depression, and was started on sertraline. In the month before the consultation, she also had a neurological work-up with negative computed tomography scans of the head and normal electroencephalogram. Her family history was significant only for diabetes of a maternal aunt. She denied allergies or use of cigarettes, alcohol, or illicit drugs. She was taking sertraline, 50 mg daily for the past year; ethinyl estradiol/norgestimate, one daily for the past 2 years; and oxcarbazepine, 175 mg twice daily for the …