Hyperglucagonemia in myotonic dystrophy.

To clarify the possible participation of glucagon in glucose intolerance in myotonic dystrophy, six patients with myotonic dystrophy were examined. Three of the six patients had abnormal oral glucose tolerance curves; two had frank diabetic glucose tolerance curves, and the other had a high glucose value 30 min after glucose loading, which fell beyond the normal range (mean +/- 2 SD). The total insulin response to oral glucose, calculated as the insulin area, was significantly exaggerated (P less than 0.01 vs. the control value). In addition to these results, hyperglucagonemia was observed throughout the test in two patients with myotonic dystrophy. In the arginine infusion test, the insulin response was not as exaggerated. Plasma glucagon, however, was significantly higher (P less than 0.05 vs. the control value) 30, 45, and 60 min after arginine infusion, and the mean glucagon area under the curves was significantly greater (P less than 0.05 vs. the control value). None of the myotonic patients showed GH or cortisol excess during an arginine infusion and/or insulin tolerance test. Three patients with myotonic dystrophy who had abnormal glucose tolerance curves showed absolutely or relatively high glucagon levels and exaggerated responses to arginine infusion. These findings suggested that hyperglucagonemia might contribute to the appearance of glucose intolerance in myotonic dystrophy.