The Metabolic Syndrome | Harrison's Endocrinology, 4e | AccessBiomedical Science

INTRODUCTION

The metabolic syndrome (syndrome X, insulin resistance syndrome) consists of a constellation of metabolic abnormalities that confer increased risk of cardiovascular disease (CVD) and diabetes mellitus. Evolution of the criteria for the metabolic syndrome since the original definition by the World Health Organization in 1998 reflects growing clinical evidence and analysis by a variety of consensus conferences and professional organizations. The major features of the metabolic syndrome include central obesity, hypertriglyceridemia, low levels of high-density lipoprotein (HDL) cholesterol, hyperglycemia, and hypertension (Table 22-1).

TABLE 22-1NCEP:ATPIII^a 2001 AND HARMONIZING DEFINITION CRITERIA FOR THE METABOLIC SYNDROME

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TABLE 22-1 NCEP:ATPIII^a 2001 AND HARMONIZING DEFINITION CRITERIA FOR THE METABOLIC SYNDROME

NCEP:ATPIII 2001

HARMONIZING DEFINITION^b

Three or more of the following:

• Central obesity: waist circumference >102 cm (M), >88 cm (F)

• Hypertriglyceridemia: triglyceride level ≥150 mg/dL or specific medication

• Low HDL^c cholesterol: <40 mg/dL and <50 mg/dL for men and women, respectively, or specific medication

• Hypertension: blood pressure ≥130 mmHg systolic or ≥85 mmHg diastolic or specific medication

• Fasting plasma glucose level ≥100 mg/dL or specific medication or previously diagnosed type 2 diabetes

Three of the following:

• Waist circumference (cm)

Men

Women

Ethnicity

≥94

≥80

Europid, sub-Saharan African, Eastern and Middle Eastern

≥90

≥80

South Asian, Chinese, and ethnic South and Central American

≥85

≥90

Japanese

• Fasting triglyceride level >150 mg/dL or specific medication

• HDL cholesterol level <40 mg/dL and <50 mg/dL for men and women, respectively, or specific medication

• Blood pressure >130 mm systolic or >85 mm diastolic or previous diagnosis or specific medication

• Fasting plasma glucose level ≥100 mg/dL (alternative indication: drug treatment of elevated glucose levels)

^aNational Cholesterol Education Program and Adult Treatment Panel III.

^bIn this analysis, the following thresholds for waist circumference were used: white men, ≥94 cm; African-American men, ≥94 cm; Mexican-American men, ≥90 cm; white women, ≥80 cm; African-American women, ≥80 cm; Mexican-American women, ≥80 cm. For participants whose designation was “other race—including multiracial,” thresholds that were once based on Europid cutoffs (≥94 cm for men and ≥80 cm for women) and on South Asian cutoffs (≥90 cm for men and ≥80 cm for women) were used. For participants who were considered “other Hispanic,” the International Diabetes Federation thresholds for ethnic South and Central Americans were used.

^cHigh-density lipoprotein.

EPIDEMIOLOGY

The most challenging feature of the metabolic syndrome to define is waist circumference. Intraabdominal circumference (visceral adipose tissue) is considered most strongly related to insulin resistance and risk of diabetes and CVD, and for any given waist circumference the distribution of adipose tissue between SC and visceral depots varies substantially. Thus, within and between populations, there is a lesser vs. greater risk at the same waist circumference. These differences in populations are reflected in the range of waist circumferences considered to confer risk in different geographic locations (...