Metabolic syndrome overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-In-Chief: Priyamvada Singh, M.B.B.S. [2]
Overview
Metabolic syndrome are characterized by a cluster of conditions that greatly increases the risk of a person to develop heart diseases, diabetes and stroke. By definition one is said to have a metabolic syndrome if they have 3 of the following 5 conditions: high blood pressure (>130/85), abnormal fasting blood glucose > 100 mg/dl, increased weight around the waist (women > 35 inches, male > 40 inches), triglycerides > 150 mg/dl and a low HDL (female < 50, male < 40).[1]
Historical Perspective
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.
Pathophysiology
The pathophysiology is extremely complex and has only been partially elucidated. Most patients are older, obese, sedentary, and have a degree of insulin resistance. The most important factors in order are 1) aging, 2) genetics and 3) lifestyle (i.e., decreased physical activity and excess caloric intake).
Causes
Metabolic syndrome is becoming more and more common in the United States. Researchers are not sure whether the syndrome is due to one single cause, but all of the risks for the syndrome are related to obesity.
Differentiating Metabolic Syndrome from other Diseases
Metabolic syndrome occurs in the presence of insulin resistance and accompanying obesity. It increases the risk for coronary heart disease, diabetes, fatty liver, stroke and some cancers. It may manifests as hypertension, hyperglycemia, hypertriglyceridemia, or reduced high-density lipoprotein cholesterol. The differential diagnosis includes chronic liver disease, Cushing syndrome and congenital adrenal hyperplasia with overlapping presentations.
Epidemiology and Demographics
The prevalence of metabolic syndrome has increased over the decades. The prevalence are higher in western countries, with increasing ages and in certain races like Mexican-Americans and African-Americans.
Risk Factors
Metabolic syndrome is becoming more and more common in the United States. Researchers are not sure whether the syndrome is due to one single cause, but all of the risks for the syndrome are related to obesity.
Natural History, Complications and Prognosis
Metabolic syndrome occurs in the presence of insulin resistance and accompanying obesity. It increases the risk for coronary heart disease,diabetes, fatty liver, stroke and some cancers. It may manifests as hypertension, hyperglycemia, hypertriglyceridemia, reduced high-density lipoprotein cholesterol and abdominal obesity.
Diagnosis
Diagnostic Criteria
There are currently two major definitions for metabolic syndrome provided by International Diabetes Federation[2] 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.
History and Symptoms
The diagnosis of metabolic syndrome is mostly based on physical examination and lab tests. The symptoms seen in metabolic syndrome are indicative of the component disorder like hypertension, diabetes, dyslipidemia and polycystic ovarian syndrome. Also, dietary, family, social and medical history are important tools in the diagnosis.
Physical Examination
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.
Laboratory Findings
The diagnosis of metabolic syndrome is mostly based on physical examination and lab tests. The diagnostic criteria of different international societies also involves consideration of lab tests like lipid profile and fasting blood glucose.
Electrocardiogram
Electrocardiograms are not routinely used in diagnosing metabolic syndrome. However, they can be used when patients with metabolic syndrome develops cardiovascular complications like angina, myocardial infarction or stroke.
Chest X Ray
A Chest X-ray is not routinely used in diagnosing metabolic syndrome. However, they can be used as an additional test when patients with metabolic syndrome develops cardiovascular complications like angina, myocardial infarction or stroke.
Treatment
Dietary Therapy
Dietary modifications are the first step in treatment of metabolic syndrome. It can be started in isolation or along with other medications. It helps by assisting in weight loss, thus increasing insulin sensitivity. Studies support that diet, exercise, and drug therapy may inhibit the progression of metabolic syndrome to diabetes mellitus.
Physical Activity
Regular aerobic exercises are thought to beneficial in decreasing the risks for the development of metabolic syndrome. Exercise may benefit by helping in weight reduction that in turn increases insulin sensitivity of the liver and other tissues.
Medical Therapy
The first line treatment is change of lifestyle (i.e., caloric restriction, physical activity, weight loss). However, drug treatment is frequently required for complications that are seen with them.
Surgery
Surgical therapy is not routinely performed for metabolic syndrome. However, in cases of morbid obesity and unresponsiveness of medical therapy bariatric surgery can be performed. The beneficial effects of surgery is thought to be due to the weight loss after surgery that in turn decreases the insulin resistance. Also, increased secretion of gut hormones such as glucagon-like peptide-1 (GLP-1) accompanies the surgery and thus helps in metabolic syndrome.
Primary Prevention
Primary prevention strategies intend to avoid the development of disease. Different strategies like dietary modification, increasing physical activity and weight reduction are found useful in the primary prevention (development) of metabolic syndrome.