Evaluation of insulin receptor in myotonic dystrophy.

Only 2 of 6 patients with myotonic dystrophy had glucose intolerance and hyperinsulinemia. All, however, had markedly reduced insulin binding to specific receptors on circulating monocytes. A significant difference in receptor affinity for insulin was observed, but the difference in affinity was not as marked as that in the amount of 125I-insulin bound per cell, which was sixfold greater in control cells. No evidence for a circulating factor competing with insulin for binding sites could be demonstrated. These alterations in binding did not directly correlate with glucose intolerance or hyperinsulinemia and are consistent with a postulated generalized membrane defect. Study of the insulin receptor in this disorder may uncover regulatory mechanisms in normal and pathological conditions, including myotonic dystrophy.