The metabolic syndrome: insulin resistance.

Insulin resistance is the most accepted unifying theory explaining the pathophysiology of the metabolic syndrome. However, epidemiologic studies indicate that a substantial proportion of patients with the metabolic syndrome do not have evidence of insulin resistance, and the correlation between insulin resistance and individual components of the syndrome is weak to moderate. Insulin resistance may play an important role in the development of hyperglycemia and dyslipidemia, which can further aggravate insulin resistance. The implication of insulin resistance in hypertension appears to be less strong than its role in causing hyperglycemia and dyslipidemia. Obesity may be another pathogenic factor in the metabolic syndrome that may help initiate or worsen insulin resistance. However, like insulin resistance, obesity is not universal in the metabolic syndrome, and many obese subjects do not have metabolic abnormalities. This review provides an update on the relationship between insulin resistance and main components of the metabolic syndrome: hyperglycemia, dyslipidemia, hypertension, and obesity.