The insulin resistance syndrome.

Insulin resistance is a frequently occurring abnormality. Although there can be insensitivity to any of insulin's actions, insulin resistance par excellence is a decreased insulin-mediated whole-body glucose disposal rate. A distinction is made between primary and secondary insulin resistance. Primary insulin resistance is of unknown origin, is only partially experimentally reproducible, and is essentially irreversible (spontaneously or by treatment). In addition, it is both pathway-specific (ie, glucose storage) and organ-specific (mostly skeletal muscle), and is compatible with a postreceptor defect in insulin action. Primary insulin resistance is found in a proportion (approximately 25%) of otherwise healthy people, in non-insulin-dependent diabetes mellitus, essential hypertension, and some forms of dyslipidemia. The idea of an insulin resistance syndrome derives from the striking pattern of overlap among these clinical conditions. Their tendency to cluster in the same individuals is evident from both cross-sectional and longitudinal observations. It is proposed that the insulin resistance syndrome is a large constellation of interrelated changes in metabolic, anthropometric, and hemodynamic variables centered around insulin resistance or hyperinsulinemia. There is a significant genetic component, a predisposing influence for non-insulin-dependent diabetes mellitus, hypertension, dyslipidemia, and possibly, a distinct atherogenic potential.