[Successful treatment of recurrent hypoglycemia by pioglitazone in a patient with myotonic dystrophy].

A 20 year-old woman with myotonic dystrophy type 1 (DM1) presented with fatigue, daytime somnolence, and sudden poor responsiveness. Blood glucose was measured before and after each meal for 4 days, and hypoglycemia was confirmed twice, although neither perspiration nor palpitations occurred in the hypoglycemic state. On a 75 g oral glucose tolerance test (OGTT), fasting blood glucose level was 83 mg/dl, and fasting blood immunoreactive insulin (IRI) level was 5.96 microIU/ml. However, IRI increased to 528 microIU/ml at 60 minutes and blood glucose decreased to 57 mg/dl at 120 minutes of the OGTT. The patient was diagnosed with reactive hypoglycemia due to excessive insulin secretion. Oral administration of pioglitazone improved the excessive insulin secretion as assessed by OGTT. After starting treatment, hypoglycemia was not detected either pre- or post-prandially. After 10 months of treatment, blood glucose level after glucose loading was higher than fasting blood glucose level during OGTT, and the IRI area under the curve of the OGTT decreased. We considered that hypoglycemia unawareness resulted from recurrent hypoglycemic episodes in this patient. Pioglitazone was effective in improving hyperinsulinemia and reactive hypoglycemia in nondiabetic DM1.