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Tackling impaired glucose tolerance

Q What should we do about impaired fasting glucose/glucose tolerance?

A Impaired glucose tolerance (IGT) represents an abnormality in glucose regulation in the postprandial state. Impaired fasting glucose (IFG) represents an abnormality in glucose regulation in the fasting state.

Patients with either may be euglycaemic in their daily lives as shown by normal or near normal HbA1c. One-third of patients with either IFG or IGT and two-thirds of those with both will develop type 2 diabetes within six years.

IGT is a marker of insulin resistance that is intimately linked to the metabolic syndrome (hypertension, obesity and dyslipidaemia).

Compared with normoglycaemic patients, patients with IGT have a two-to five-fold increased incidence of new onset cardiovascular ischaemia, fatal and total myocardial infarction and stroke, independent of progression to diabetes. It should, however, also be noted that the glucose tolerance test is variable. If levels at two hours are close to diabetes mellitus, a repeat may confirm diabetes mellitus.

There is now compelling evidence that type 2 diabetes can be delayed or prevented in patients with IGT. Intensive lifestyle intervention involving exercise and dietary change, of which weight loss is an indicator, reduced the total incidence of diabetes in patients with IGT by 58 per cent in the US Diabetes Prevention Programme.

Assessment for macrovascular risk should include blood pressure and fasting lipid profile. Most patients will need a statin, antihypertensive treatment and aspirin.

Adeeba Ahmed is specialist registrar at Central Middlesex Hospital, London

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