Impaired glucose tolerance

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Impaired fasting glucose (IFG) and impaired glucose tolerance (IGT) are intermediate between normal and diabetic.
Progression to overt DM is not straight-forward.[1]

LogoKeyPointsBox.pngAppropriate lifestyle modification in impaired glucose tolerance results in sustained benefit, reducing the progression to frank diabetes mellitus of the same or greater magnitude than using a drug like metformin or rosiglitazone both of which only seem to work while being taken.

The American Agency for Healthcare Research and Quality published a systematic review [1] in September 2005 that showed aggressive lifestyle modification is beneficial. This appears to be the most comprehensive overview of IGT written, to date. This reported, for instance, that aggressive lifestyle interventions resulted in a significantly lower progression to diabetes compared with metformin (4.8 percent versus 7.8 percent per year; relative risk reduction 0.39, 95% CI 0.24 to 0.51), especially in individuals 60 years of age or older.

The Diabetes primary prevention trial and the Diabetes protection study, large scale European and American studies suggest that when we identify impaired glucose tolerance (IGT), starting metformin is a reasonable idea, with the aim of slowing or avoiding the progression to actual diabetes mellitus.

The DREAM study has established that treating 7 patients with impaired fasting glucose or impaired glucose tolerance by Rosiglitazone for 3 years will prevent 1 from progressing to diabetes so rosiglitazone is likely to be beneficial. [2] Ramipril did not have such benefit, even if it normalised blood glucose so is unlikely to be benefical.[3]

Whether one can identify insulin resistance (or even IGT!) by eye and whether metformin is justifiable in that case is another matter. At pence per day, and with a small appetite suppressant effect, pretreating with metformin fat people who are not formally diabetic yet is not wholly stupid. Evidence for its effectiveness is deficient and we do not have cost effectiveness analysis yet compared to rosiglitazone. Appropriate lifestyle modification is much more cost effective and as its benefit is sustained, more clinically effective, than any drug on present evidence.


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