Describe Metabolic Syndrome ?

As discussed, the risk factors like obesity, high blood pressure, high blood glucose or impaired glucose tolerance, and dyslipidaeinia are very important from the pathogenetic point of view. While each of these factors can be present singly and cad cause or predispose to Cardio-vascular diseases individually, more often than not they are clustered together in the same person, multiplying the risk several fold. The term 'Metabolic syndrome ' is applied to the clustering of these risk factors and the rising incidence of this syndrome is considered to be the main cause of increasing number of Cardio-vascular diseases and diabetes, especially in the Indian subcontinent, Though the clustering of the risk factors was not unknown earlier, it was only in 1988 that the concept of a syndrome with these clustered abnormalities was put forward by Prof Gerald Reavan in his famous Banting lecture and he coined the term syndrome X to describe that grouping, As insulin resistance was thought to be the primary mechanism underlying these abnormalities, the name insulin resistance syndl.omc was also applied. Subsequently metabolic syndrome became the term of choice when WHO in 1999 and The Third Report of the National Cholesterol Education Program's Adult Treatinen1 Panel (NCEP ATP-111) independently developed the criteria using that name.

A general definition of the metabolic syndrome is: "A collection of metabolic abnormalities associated with insulin resistance that predisposes affected individuals to accelerated atherosclerosis and consequently increased risk of Cardio-vascular events". The component of the metabolic syndrome, as the name suggests, is of metabolic origin and consist of atherogenic dyslipidaemia (low HDL cholesterol, high triglyceridcs, increased small dense LDL), elevated blood glucose, elevated blood pressure and obesity. Two other abnormalities are present in the background a pro-inflammatory state characterised by elevations of circulating cytokines and acute phase reactants (like C-reactive protein) and a prothrombotic state indicated by increases in fibrinogen, factor VII, plasminogen activator inhibitor- 1 (PAI-I), It is now clear that metabolic syndrome is a multifactorial and multiplex disorder with a complex, mutually reinforcing interaction between insulin resistance and obesity.

Various criteria have been put forward for the diagnosis of metabolic syndrome. The World Health Organisation definition in 1999 included clinical evidence of insulin resistance, such as impaired glucose tolerance, impaired fating glucose or type two diabetes as necessary for the diagnosis, 'ho other risk factors were also required: low HDL cholesterol or elevated triglyceride, Hypertension, obesity, or rnicroalbuininuria. NCEP ATP-111 proposed a simple set of diagnostic criteria based on common clinical variables including waist circumference, HDL-C, tsiglyceride, blood pressure and fasting glucose level in the blood. The presence of defined abnormalities in any three of the five variables was sufficient for the diagnosis. International Diabetes Federation (IDF) has come up recently with a simplified definition for global use. In their definition proposed in 2005, central obesity was made the core feature. IDF concluded that abdominal obesity incorporates both the concepts of obesity and insulin resistance as being two major underlying risk factors of metabolic syndrome and that waist circumference measurement is the simplest examination that can be used to identify individuals who are likely candidates for this condition. IDF made waist circumference thresholds ethnic-specific with lower thresholds in individuals or ethnic groups, such as South Asians, who are prone to insulin resistance. The ATP-III update and IDF criteria more or less identify the same individuals with metabolic syndrome. However IDF simplifies the diagnosis in developing counties to save resources; only individuals exceeding waist size threshold will require further laboratory studies to clinch the diagnosis.

Metabolic syndrome significantly increases the risk of Cardio-vascular diseases (CVD) and diabetes. In fact the interest in metabolic syndrome stemmed from the observation of a close correlation between the rising incidence of CVD and the salient features of this condition, particularly abdominal obesity and insulin resistance. The relative risk of CAD ranges from 1.5 to 3 depending on the stage of progression and the risk of diabetes increases five-fold compared to those without metabolic syndrome. The development of diabetes increases the Cardio-vascular risk still further. In the NHANES I11 study, the age adjusted prevalence of coronary artery disease was highest (19.2 per cent) in patients with both type two diabetes and metabolic syndrome, followed by metabolic syndrome without type two diabetes (13.9 per cent). Increased risks of CAD and/or all cause mortality have been demonstrated in Nurses' Health study and in AFCAPS/TexCAPS also.

Another important point to note is that multiple risk factors present in metabolic syndrome have a multiplicative effect; risk rises geometrically instead of linearly, being more than the sum of risks ascribed to.individua1 risk factors. A person must have Central obesity (defined as waist circumference >I= 94 cm for Europid men and >/= 80 cm for Europid women, with ethnicity specific values for other groups.