The term "metabolic syndrome" refers to a clustering of specific cardiovascular disease (CVD) risk factors whose underlying pathophysiology is thought to be related to insulin resistance. Since the term is widely used in research and clinical practice, we undertook an extensive review of the literature in relation to the syndrome's definition, underlying pathogenesis, and association with CVD and to the goals and impact of treatment. While there is no question that certain CVD risk factors are prone to cluster, we found that the metabolic syndrome has been imprecisely defined, there is a lack of certainty regarding its pathogenesis, and there is considerable doubt regarding its value as a CVD risk marker. Our analysis indicates that too much critically important information is missing to warrant its designation as a "syndrome." Until much needed research is completed, clinicians should evaluate and treat all CVD risk factors without regard to whether a patient meets the criteria for diagnosis of the "metabolic syndrome." Diabetes Care 28:2289 -2304, 2005F or most of the 20th century, cardiovascular disease (CVD) was identified as the major cause of morbidity and mortality in the developed world. During this period there was considerable effort to understand the underlying biology of the disease and to identify the contributing risk factors. As risk factors were identified, it became apparent that more than one were often present in the same individual. Toward the end of the century, the clustering of CVD risk factors was first described, most notably the simultaneous presence of obesity, type 2 diabetes, hyperlipidemia, and hypertension (1-3). Although insulin resistance (i.e., resistance to insulin-stimulated glucose uptake) as a feature of type 2 diabetes was first described many years earlier (4), hyperinsulinemia was also found to be a key feature of type 2 diabetes (5,6), as well as hyperlipidemia (7-9), obesity (10 -13), and hypertension (12)(13)(14). In addition, a cluster of heart disease risk factors seemed clearly related to type 2 diabetes (15).This risk factor clustering, and its association with insulin resistance, led investigators to propose the existence of a unique pathophysiological condition, called the "metabolic" (1-3) or "insulin resistance" (11) syndrome. This concept was unified and extended with the landmark publication of Reaven's 1988 Banting Medal award lecture (16). Reaven postulated that insulin resistance and its compensatory hyperinsulinemia predisposed patients to hypertension, hyperlipidemia, and diabetes and thus was the underlying cause of much CVD. Although obesity was not included in Reaven's primary list of disorders caused by insulin resistance, he acknowledged that it, too, was correlated with insulin resistance or hyperinsulinemia, and that the obvious "treatment" for what he termed "syndrome X" was weight maintenance (or weight loss) and physical activity.Reaven's seminal paper was followed by many studies documenting the clustering of CVD risk factors and their relatio...

Background: The term 'metabolic syndrome' refers to a clustering of specific cardiovascular disease (CVD) risk factors whose underlying pathophysiology is thought to be related to insulin resistance. Methods: Since the term is widely used in research and clinical practice, we undertook an extensive review of the literature in relation to the syndrome's definition, underlying pathogenesis, association with cardiovascular disease and to the goals and impact of treatment. Discussion: While there is no question that certain CVD risk factors are prone to cluster, we found that the metabolic syndrome has been imprecisely defined, there is a lack of certainty regarding its pathogenesis, and there is considerable doubt regarding its value as a CVD risk marker. Our analysis indicates that too much critically important information is missing to warrant its designation as a 'syndrome'. Conclusion: Until much-needed research is completed, clinicians should evaluate and treat all CVD risk factors without regard to whether a patient meets the criteria for diagnosis of the 'metabolic syndrome'.

The prevalence of non-insulin-dependent diabetes mellitus (NIDDM) is higher in Mexican Americans than in non-Hispanic white Americans, even after adjustment for the former's greater overall and more centralized adiposity. We postulated that this excess risk of NIDDM could be due to resistance to insulin. We performed oral glucose-tolerance tests with measurements of serum insulin concentrations in 225 Mexican Americans and 180 non-Hispanic whites without diabetes as part of the San Antonio Heart Study, a population-based study of risk factors for diabetes. Changes in serum insulin concentrations in response to the glucose challenge were quantified by the area under the serum insulin curve. Overall adiposity was characterized by body-mass index, and regional body-fat distribution by the ratio of subscapular to triceps skinfolds and the ratio of waist to hip circumference. After adjustment for these indicators of adiposity and also for differences in glucose tolerance, Mexican Americans were found to have significantly greater areas under the serum insulin curve than non-Hispanic whites. These data suggest that, like other populations at high risk for NIDDM such as Pima Indians and Micronesians, Mexican Americans have more hyperinsulinemia than can be accounted for by their adiposity.

The purpose of this study was to estimate the prevalence of diagnosed and undiagnosed diabetes among Mexican Americans, Cubans, and Puerto Ricans in the United States and compare these estimates to data from prior surveys for U.S. non-Hispanic whites and blacks. Data for this study are from the Hispanic Health and Nutrition Examination Survey, a multipurpose cross-sectional survey of three U.S. Hispanic populations conducted in 1982-1984. The interviewed sample of people aged 20-74 yr included 3935 Mexican Americans in the southwest, 1134 Cubans in Florida, and 1519 Puerto Ricans in the New York City area. The diabetes component consisted of interview questions on diabetes diagnosis and treatment and an oral glucose tolerance test administered to a subsample. The prevalence of diabetes was two to three times greater for Mexican Americans and Puerto Ricans than for non-Hispanic whites surveyed in 1976-1980. In Cubans, the prevalence was similar to that for non-Hispanic whites. In men and women 45-74 yr of age, the prevalence of diabetes was extremely high for both Mexican Americans (23.9%) and Puerto Ricans (26.1%) compared with Cubans (15.8%) or non-Hispanic whites (12%). The total prevalence of diabetes was not significantly different for Mexican Americans and Puerto Ricans but was significantly lower for Cubans. The relatively lower prevalence of diabetes among Cubans and the high prevalence in both Mexican Americans and Puerto Ricans may be related to socioeconomic, genetic, behavioral, or environmental factors.