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Syndrome X (obesity/insulin resistance/hypertension/lipids)

Last reviewed Jan 16, 2024

The National Cholesterol Education Program (NCEP) Adult Treatment Panel (ATP) III guidelines suggested that a diagnosis of metabolic syndrome (previously known as syndrome X) where three or more of the following risk factors are present:

central obesity
elevated triglyceride
low HDL
raised blood pressure
raised fasting plasma glucose

More recently the International Diabetes Federation (IDF) (3) have defined criteria for metabolic syndrome where metabolic syndrome is diagnosed if the patient has a 'large waist' plus any other two risk factors.

Risk Factor	Defining Level NCEP ATP III Any three of these:	Defining criteria IDF Large waist plus any two:
Central (abdominal) obesity* waist circumference	men > 102 cm (>40 in) women > 88 cm (>35 in)	men > 94 cm (> 37 inches) women > 80 cm (> 32 inches)
high-density lipoprotein cholesterol	men <1.0 mmol/L (<40mg/dL) women <1.3 mmol/L (<50mg/dL)	men < 1.0 mmol/L (40 mg/dL) women <1.3 mmol/L (50 mg/dL)
triglycerides	>= 1.7 mmol/L (>= 150mg/dL)	>= 1.7 mmol/L (>=150 mg/dL)
blood pressure	>= 130/85 mmHg	>= 130/85 mmHg
fasting plasma glucose	>= 6.6 mmol/L (>=110mg/dL)	>= 5.6 mmol/l (>=100 mg/dL)

Interestingly the IDF criteria suggests a smaller waist circumference (for men and women) and also a lower fasting glucose level.

* central obesity is more highly correlated with the metabolic risk factors than body mass index (BMI) and therefore measurement of waist circumference (around the navel) is recommended to identify the bodyweight component of metabolic syndrome

The metabolic syndrome:

is a collection of both non-lipid and lipid risk factors of metabolic origin
insulin resistance is the basic underlying mechanism
- obesity probably leads to insulin resistance by the associated increased rate of non-esterified fatty acids causing post-receptor defects in insulin's action. Other mechanisms include mutation of gene encoding insulin receptor; circulating autoantibodies to the extracellular domain of the insulin receptor
- insulin resistance is associated with:
  - obesity
  - being of Asian origin
  - pregnancy
  - acromegaly
  - polycystic ovaries
  - cystic fibrosis
  - ataxia telangiectasia
  - acute and chronic renal failure
  - Prader-Willi syndrome
  - Werner's syndrome
  - drugs including rifampicin, isoniazid
increases CHD risk at any given LDL level
first-line therapies (1) are:
- weight reduction
- increased physical activity - regular physical activity reduces very low-density lipoprotein (VLDL) levels, blood pressure and insulin resistance and can have beneficial effects on cardiovascular function
- LDL reduction
also treatments for hypertension, plus aspirin and treatments to reduce triglycerides and elevate HDL, have also been shown to reduce coronary heart disease risk (1)
other lifestyle factors (in addition to physical activity) must be addressed e.g. moderation in alcohol intake, and cessation of smoking and monosaturated fat in the diet

Notes:

the IDF define waist circumference based on different population groups (3)
- increased waist circumference for South Asians
  - Male >= 90 cm
  - Female >= 80 cm
- increased waist circumference for Chinese
  - Male >= 90 cm
  - Female >= 80 cm

Reference:

Executive Summary of the third report of the National Cholesterol Education Program (NCEP) expert panel on detection, evaluation and treatment of high blood cholesterol in adults (Adult Treatment Panel III) JAMA 2001; 285:2486-97.
Reaven GM. Role of insulin resistance in human disease. Diabetes 1983; 37:1595-1607.
www.idf.org

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Syndrome X (obesity/insulin resistance/hypertension/lipids)

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