Mechanisms of insulin resistance in human obesity: evidence for receptor and postreceptor defects.

(a) decreased cellular insulin receptors contribute to the insulin resistance associated with human obesity in all subjects; (b) in the least hyperinsulinemic, insulin-resistant patients, decreased insulin receptors are the sole defect, whereas in the more hyperinsulinemic, insulin-resistant patients, the insulin resistance is the result of a combination of receptor and postreceptor abnormalities; (c) all obese patients were insensitive to insulin's suppressive effects on hepatic glucose output; this was entirely the result of decreased insulin receptors; no postreceptor defect in this insulin effect was demonstrated.