Syndrome X: 6 years later.

Resistance to insulin-stimulated glucose uptake is a common phenomenon, occurring in approximately 25% of the population at large, and is associated with a number of conditions known to be risk factors for coronary heart disease (CHD). These include hyperinsulinaemia, abnormal glucose tolerance, non-insulin-dependent diabetes mellitus, increased plasma triglyceride and decreased high-density-lipoprotein cholesterol concentrations, smaller, denser low-density-lipoprotein particles, hypertension, and abnormalities of fibrinolysis. These abnormalities frequently occur in a cluster within individuals. Understanding the basis of these changes, as well as the interrelationships between them, will contribute substantially to future studies of the causes of CHD, and ultimately form the basis for the clinical management of insulin-resistant individuals.