Metabolic syndrome is a combination of medical disorders that increase the risk of developing cardiovascular disease and diabetes. It affects a great number of people, and prevalence increases with age. Some studies estimate the prevalence in the USA to be up to 25% of the population.

Metabolic syndrome is also known as metabolic syndrome X, syndrome X, insulin resistance syndrome, Reaven's syndrome, and CHAOS (Australia). A similar condition in overweight horses is referred to as equine metabolic syndrome; it is unknown if they have the same etiology.

Signs and symptoms

Symptoms and features are:

• Fasting hyperglycemia — diabetes mellitus type 2 or impaired fasting glucose, impaired glucose tolerance, or insulin resistance;
• High blood pressure;
• Central obesity (also known as visceral, male-pattern or apple-shaped adiposity), overweight with fat deposits mainly around the waist;
• Decreased HDL cholesterol;
• Elevated triglycerides;

Associated diseases and signs are: elevated uric acid levels, fatty liver (especially in concurrent obesity), progressing to non-alcoholic fatty liver disease, polycystic ovarian syndrome, hemochromatosis (iron overload); and acanthosis nigricans (a skin condition featuring dark patches).

Diagnosis

There are currently two major definitions for metabolic syndrome provided by the International Diabetes Federation and the revised National Cholesterol Education Program, respectively. The revised NCEP and IDF definitions of metabolic syndrome are very similar and it can be expected that they will identify many of the same individuals as having metabolic syndrome. The two differences are that IDF excludes any subject without increased waist circumference, while in the NCEP definition metabolic syndrome can be diagnosed based on other criteria and the IDF uses geography-specific cut points for waist circumference, while NCEP uses only one set of cut points for waist circumference regardless of geography. These two definitions are much closer to each other than the original NCEP and WHO definitions.

WHO

The World Health Organization criteria (1999) require presence of diabetes mellitus, impaired glucose tolerance, impaired fasting glucose or insulin resistance, AND two of the following:

• blood pressure: ≥ 140/90 mmHg
• dyslipidaemia: triglycerides (TG): ≥ 1.695 mmol/L and high-density lipoprotein cholesterol (HDL-C) ≤ 0.9 mmol/L (male), ≤ 1.0 mmol/L (female)
• central obesity: waist:hip ratio > 0.90 (male); > 0.85 (female), and/or body mass index > 30 kg/m²
• microalbuminuria: urinary albumin excretion ratio ≥ 20 mg/min or albumin:creatinine ratio ≥ 30 mg/g