Biphasic response on oral glucose tolerance testing in myotonic dystrophy.

Oral glucose tolerance tests have been carried out on 40 patients with myotonic dystrophy, and 50 hospitalized control patients. A biphasic response was found in 19 myotonic dystrophy patients (49 per cent), compared with 12 of the control population (24 per cent). In 9 patients with myotonic dystrophy (23 per cent), the height of the second peak was greater than or equal to 20 mg/100 ml, the corresponding figure for the control group being 2 patients (4 per cent) (P less than 0.005).