THIAZIDES AND DIABETES RISK

Potassium Changes Mediate Thiazide-Induced Diabetes

NEW YORK (Reuters Health) Dec 05 - The increased risk for diabetes in patients taking thiazide diuretics appears to be mediated by changes in serum potassium levels, according to a report in the December issue of Hypertension.

"It has been speculated for some time that potassium loss from the body due to diuretic use could lead to diabetes," lead author Dr. Tariq Shafi, from Johns Hopkins University, Baltimore, told Reuters Health. In the current study, "loss of potassium from the body with resulting lowering of potassium levels in blood explained most of the risk of diabetes from thiazides."

The results also indicated that if a patient does not develop diabetes within 1 year of starting thiazide therapy, then diabetes that develops afterward is likely not thiazide-induced.

The study featured an analysis of data on 3790 nondiabetic subjects enrolled in the Systolic Hypertension in Elderly Program, a randomized trial involving treatment with chlorthalidone or placebo. Diabetes was defined by use of antidiabetic agents, self report, fasting glucose of 126 mg/dL or higher, or a random glucose of 200 mg/dL or higher.

During 1 year of follow-up, chlorthalidone use doubled the risk of diabetes. After accounting for the change in potassium levels, the risk was markedly reduced, which supports a mediating effect.

Each 0.5-mEq/L drop in serum potassium was independently linked to a 45% increase in diabetes risk (p <>

As noted, beyond 1 year, chlorthalidone use was not significantly associated with diabetes risk, the report shows.

"Thiazide diuretics are very effective for control of blood pressure," Dr. Shafi emphasized. "Clinicians have been reluctant to use it for treatment of hypertension because of the risk of diabetes among other things. Our study suggests that taking adequate amounts of potassium, either in diet or as supplements, might prevent diabetes and will allow the use of these cheap and highly effective medications."

Nonetheless, data from randomized trials are needed to determine if, in fact, preventing potassium loss can cut the risk of diabetes, he said.