Metabolic syndrome

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What is it?

Metabolic syndrome is a set of risk factors that includes: abdominal obesity, a decreased ability to process glucose (insulin resistance), dyslipidaemia, and hypertension. Patients who have this syndrome have been shown to be at an increased risk of developing cardiovascular disease and/or type 2 diabetes. Metabolic syndrome is a common condition that goes by many names (dysmetabolic syndrome, syndrome X, insulin resistance syndrome and obesity syndrome) but few outside the medical community have heard of it. Most patients have been educated about the importance of checking their cholesterol levels, watching for signs of diabetes, having their blood pressure monitored, and exercising – but there has been little to tie all of these factors together except pursuit of a 'healthier lifestyle'.

The World Health Organization (WHO) was the first to publish an internationally accepted definition for metabolic syndrome in 1998, but the criteria that have received the most widespread acceptance and use are those proposed as part of ATP III (the third report of the National Cholesterol Education Program expert panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults).

ATP III defines metabolic syndrome as involving three or more of the following:

  • Central/abdominal obesity as measured by waist circumference
    Men - greater than 102 cm (40 inches);
    Women - greater than 88 cm (35 inches)
  • Fasting triglycerides greater than or equal to 1.69 mmol/L (150 mg/dL)
  • HDL cholesterol
    Men - less than 1.04 mmol/L (40 mg/dL);
    Women - less than 1.29 mmol/L (50 mg/ dL)
  • Blood pressure greater than or equal to 130/85 mm Hg
  • Fasting glucose greater than or equal to 6.1 mmol/L (110 mg/dL)

Also frequently seen with metabolic syndrome but not included with the ATP III criteria are prothrombotic (blood clotting) and proinflammatory tendencies. While these combined criteria and risk factors do not usually cause overt symptoms, they are a warning of an increased likelihood of clogged arteries, heart disease, stroke, diabetes, kidney disease, and even premature death. If left untreated, complications from untreated metabolic syndrome can develop in as few as 15 years. Those patients who have metabolic syndrome and also smoke tend to have an even poorer prognosis.

In Australia, it is estimated that 22% of adults have metabolic syndrome using the APT III criteria, with the prevalence even higher in the elderly. It can affect anyone at any age, but it is most frequently seen in those who are significantly overweight (with most of their excess fat in the abdominal area) and inactive.

The root cause of most cases of metabolic syndrome can be traced back to poor eating habits and a sedentary lifestyle. Some cases occur in those already diagnosed with hypertension and in those with poorly controlled diabetes; a few are thought to be linked to genetic factors that are still being researched.

All of the factors associated with metabolic syndrome are interrelated. Obesity and lack of exercise tend to lead to insulin resistance. Insulin resistance has a negative effect on lipid production, increasing VLDL (very low-density lipoprotein), LDL (low-density lipoprotein – the ‘bad’ cholesterol), and triglyceride levels in the bloodstream and decreasing HDL (high-density lipoprotein – the ‘good’ cholesterol). This can lead to fatty plaque deposits in the arteries which over time can lead to cardiovascular disease, blood clots and strokes. Insulin resistance also leads to increased insulin and glucose levels in the blood. Excess insulin increases sodium retention by the kidneys, which increases blood pressure and can lead to hypertension. Chronically elevated glucose levels in turn damage blood vessels and organs, such as the kidneys, and may lead to diabetes.
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