ABSTRACT

The insulin resistance syndrome (IRS), also known as the metabolic syndrome, is a “cluster” of cardiovascular (CV) risk factors that are frequently, but not always, associated with obesity. This grouping of risk factors has been known by several other synonyms including Syndrome X, deadly quartet, and cardiometabolic syndrome. Because insulin resistance describes the underlying pathophysiologic basis of the “syndrome,” it is the term used for this chapter. Reaven first drew attention to the association of insulin resistance and obesity, type 2 diabetes, high plasma triglycerides and low plasma HDL cholesterol (HDL) and hypertension (1). Since its original description there has been much experimental, clinical, and epidemiological data to support the association of this syndrome with cardiovascular disease (CVD) (2)2. Additionally, other “nontraditional” CV risk factors have been frequently included in the description of the syndrome. These include inflammation, abnormal fibrinolysis, and endothelial dysfunction and microalbuminuria (3-5). Figure 1 summarizes the relationship of these risk factors and their link with CVD. It remains unclear to what extent the components of this syndrome develop independently of each other or spring from “common soil” genetic abnormalities (6). In either case, the frequency of these coexisting abnormalities are increasing at an alarming rate, paralleling the obesity and diabetes epidemics. This is now a major clinical and public health problem-NHANES 1999-2000 estimates the prevalence of metabolic syndrome at 26.7% of US adults (7). The IRS is present in approximately 80% of persons with an established diagnosis of type 2 diabetes (8,9).