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Chapter 120: Metabolic Syndrome

INTRODUCTION

The metabolic syndrome (insulin resistance syndrome, syndrome X) is an important risk factor for cardiovascular disease and type 2 diabetes; it consists of a constellation of metabolic abnormalities that includes central obesity, insulin resistance, hypertension, dyslipidemia, high triglycerides, and low HDL. The prevalence of metabolic syndrome varies among ethnic groups; it increases with age, degree of obesity, and propensity to type 2 diabetes.

ETIOLOGY

Overweight/obesity (especially central adiposity), sedentary lifestyle, increasing age, and lipodystrophy are all risk factors for the metabolic syndrome. The exact cause is not known and may be multifactorial. Insulin resistance is central to the development of the metabolic syndrome. Increased intracellular fatty acid metabolites contribute to insulin resistance by impairing insulin-signaling pathways and accumulating as triglycerides in skeletal and cardiac muscle, while stimulating hepatic glucose and triglyceride production. Excess adipose tissue leads to increased production of proinflammatory cytokines.

CLINICAL FEATURES

There are no specific symptoms of the metabolic syndrome. The major features include central obesity, hypertriglyceridemia, low HDL cholesterol, hyperglycemia, and hypertension (Table 120-1). Associated conditions include cardiovascular disease, type 2 diabetes, nonalcoholic fatty liver disease, hyperuricemia/gout, polycystic ovary syndrome, and obstructive sleep apnea.

TABLE 120-1NCEP:ATPIIIa 2001 and Harmonizing Definition Criteria for the Metabolic Syndrome
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TABLE 120-1 NCEP:ATPIIIa 2001 and Harmonizing Definition Criteria for the Metabolic Syndrome
NCEP:ATPIII 2001 HARMONIZING DEFINITIONb

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 HDLc 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 ...

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