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 is 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). The pathophysiology of metabolic syndrome is extremely complex and has only been partially elucidated. Most patients are older, obese, sedentary, and have a degree of insulin resistance. Metabolic syndrome can be defined as a chronic state of low-grade inflammation. Common causes of metabolic syndrome include insulin resistance/hyperinsulinemia, hypertension, hypertriglyceridemia, and obesity. 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. The prevalence of metabolic syndrome varies depending on the age and ethnicity of the population studied. Dietary modifications are the first step in the management of metabolic syndrome. Medical therapy is indicated for the treatment of complications (diabetes, stroke, angina, myocardial infarction) associated with these conditions. 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.
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. In 1977, Haller coined the term "metabolic syndrome" for the first time when describing the additive effects of risk factors on atherosclerosis.
Classification
There is no established system for the classification of metabolic syndrome.
Pathophysiology
The pathophysiology of metabolic syndrome is extremely complex and has only been partially elucidated. Most patients are older, obese, sedentary, and have a degree of insulin resistance. Metabolic syndrome can be defined as a chronic state of low-grade inflammation. Numerous factors which are believed to play a key role in the pathogenesis of metabolic syndrome includes:
- Insulin resistance
- Visceral adiposity
- Atherogenic dyslipidemia
- Endothelial dysfunction
- Genetic susceptibility
- Elevated blood pressure(Hypertension)
- Hypercoagulable state
- Chronic stress
Causes
Common causes of metabolic syndrome include insulin resistance/hyperinsulinemia, hypertension, hypertriglyceridemia, and 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, 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 varies depending on the age and ethnicity of the population studied. But over the past few decades prevalence has increased many fold. It is higher in western countries, with increasing ages and in certain races like Mexican-Americans and African-Americans.
Risk Factors
Common risk factors in the development of metabolic syndrome include insulin resistance, aging, positive family history, lack of physical exercise, postmenopause, smoking, low economic status, high carbohydrate diet, atypical antipsychotics like clozapine, and soft drink consumption.
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, type II diabetes, fatty liver, stroke and some cancers. It may manifest as hypertension, hyperglycemia, hypertriglyceridemia, reduced high density lipoprotein cholesterol and abdominal obesity. 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.
Diagnosis
Diagnostic Criteria
There are currently two major definitions for metabolic syndrome provided by International Diabetes Federation (IDF) and the revised National Cholesterol Education Program (NECP), respectively. The revised National Cholesterol Education Program (NECP) and International Diabetes Federation (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 geographic-specific cut off points for waist circumference, while NCEP uses only one set of cut off 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 involve 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.
CT and MRI
There are no CT scan or MRI findings associated with metabolic syndrome.
Chest X Ray
There are no chest X-ray findings associated with metabolic syndrome.
Ultrasound
There are no ultrasound findings associated with metabolic syndrome.
Other Imaging Findings
There are no other imaging findings associated with metabolic syndrome.
Other Diagnostic Studies
Obstructive sleep apnea is sometimes considered a risk factor for metabolic syndrome. It may present as sleep disturbances, snoring and day-time drowsiness. Polysomnography can act as an important tool in diagnosing these conditions.
Treatment
Dietary Therapy
Dietary modifications are the first step in the management of metabolic syndrome. It can be initiated either 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
Metabolic syndrome is formed by a constellation of medical disorders that increases the risk of developing cardiovascular disease and diabetes mellitus. It affects a large number of people in a clustered fashion. Management of metabolic syndrome involves dietary modifications, exercise and drug therapy for the complications (diabetes, stroke, angina, myocardial infarction) found associated with these conditions.
Surgery
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. 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.
Secondary Prevention
Effective measures for the secondary prevention of metabolic syndrome in order to prevent its complication includes monitoring of lipid levels every 6 weeks, serum aminotransferase and CK levels every 6 months. Blood pressure, blood glucose, and HbA1c should be checked every 3 months.