The term "metabolic syndrome" dates back to at least the late 1950s, but came into common usage in the late 1970s to describe various associations of risk factors with diabetes, that had been noted as early as the 1920s.
Metabolic syndrome is a combination of medical disorders that increase one's risk for cardiovascular disease and diabetes. It affects a large number of people in a clustered fashion. In some studies, the prevalence in the USA is calculated as being up to 25% of the population. A condition with some similarities to human metabolic syndrome is recognised in horses. It is unknown if they have the same etiology.
It is known under various other names, such as (metabolic) syndrome X, insulin resistance syndrome, Reaven's syndrome or CHAOS (Australia).
Symptoms and features are:
Fasting hyperglycemia - diabetes mellitus type 2 or impaired fasting glucose, impaired glucose tolerance, or insulin resistance
Central obesity (also known as visceral, male-pattern or apple-shaped adiposity), overweight with fat deposits mainly around the waist
Decreased HDL cholesterol
Elevated uric acid levels
Associated diseases and signs are:
fatty liver (especially in concurrent obesity), progressing to non-alcoholic fatty liver disease
polycystic ovarian syndrome
hemochromatosis (iron overload)
acanthosis nigricans (a skin condition featuring dark patches).
Diagnosis of syndrome X
There are currently two major definitions for metabolic syndrome provided by:
1) International Diabetes Federation
2) the revised National Cholesterol Education Program.
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.
Therapy for syndrome X
The first line treatment is change of lifestyle (i.e., caloric restriction and physical activity). However, drug treatment is frequently required. Generally, the individual diseases that comprise the metabolic syndrome are treated separately (e.g. diuretics and ACE inhibitors for hypertension). Cholesterol drugs may be used to lower LDL cholesterol and triglyceride levels, if they are elevated, and to raise HDL levels if they are low. Use of drugs that decrease insulin resistance e.g., metformin and thiazolidinediones is controversial and not FDA approved.
A recent study indicated that cardiovascular exercise was therapeutic in less than 31% of cases. The most probable benefit was to triglyceride levels, with 43% showing improvement; conversely 91% of test subjects did not exhibit a decrease in fasting plasma glucose or insulin resistance. Many other studies have supported the value of increased physical activity along with restricted calories in metabolic syndrome.
Prevention of syndrome X
Various strategies have been proposed to prevent the development of metabolic syndrome. These include increased physical activity (such as walking 30 minutes every day), and a healthy, reduced calorie diet. There are many studies that support the value of a healthy lifestyle as above. However, one study stated that these measures are effective in only a minority of people. The International Obesity Taskforce states that interventions on a sociopolitical level are required to reduce development of the metabolic syndrome in populations.
A 2007 study of 2,375 male subjects over 20 years suggested that daily intake of a pint of milk or equivalent dairy products more than halved the risk of metabolic syndrome. Other studies both support and dispute the authors' findings.