MetS is a commonly occurring cluster of clinical phenotypes that are individually and collectively strongly related to cardiovascular disease.2 MetS is characterized by disturbed carbohydrate and insulin metabolism, and is clinically defined by threshold values applied to indices of central obesity, dysglycemia, dyslipidemia, and/or elevated blood pressure, which must be present concurrently in any one of a variety of combinations.2'3 The cardinal feature of MetS is abdominal obesity, as quantified most directly by increased waist circumference.4,5 Biochemically, MetS is characterized by insulin resistance - hyperinsulinemia - and by dyslipidemia - most typically raised triglycerides and/or reduced HDL cholesterol. Additionally, a range of biochemical abnormalities have been secondarily associated, including increased serum concentrations of apolipoprotein B, fibrinogen, free fatty acids, C-reactive protein (CRP), tumor necrosis factor (TNF)-a, interleukin-6, and plasminogen activator inhibitor-1, and with depressed concentrations of adiponectin. Hemodynamically, MetS is characterized by elevated blood pressure - at least in the high normal or 'prehypertensive' range (see 6.32 Hypertension). The International Diabetes Federation (IDF) has recently updated the consensus worldwide definition of MetS.6,7 It has identified both a definition for clinical practice (Table 1) and a 'platinum standard' definition that includes additional metabolic criteria that are currently used investigationally (Table 2).
Table 1 IDF metabolic syndrome definition: 2005
A person to be defined as having the metabolic syndrome must have: central obesity (defined as waist circumference >94cm for Europid men and > 80 cm for Europid women, with ethnicity-specific values for other groups) plus any two of the following four factors:
1. Raised triglyceride level: > 150mgdL- 1 (1.7mmolL -'), or specific treatment for this lipid abnormality
2. Reduced HDL cholesterol: <40 mgdL -1 (1.03 mmol L - 1#) in males and <50 mgdL-1 (1.29 mmol L-1#) in females, or specific treatment for this lipid abnormality
3. Raised blood pressure (BP): systolic BP > 130 or diastolic BP > 85 mmHg, or treatment of previously diagnosed hypertension
4. Raised fasting plasma glucose (FPG) >100mgdL- 1 (5.6mmol L-1), or previously diagnosed type 2 diabetes. (If above
5.6 mmol L- 1 or 100 mgdL- 1, oral glucose tolerance test (OGTT) is strongly recommended but is not necessary to define the presence of the syndrome)
Source: International Diabetes Federation.
Table 2 Additional metabolic syndrome criteria, for research
Abnormal body fat distribution
General body fat distribution (DXA)
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