NEW YORK A testosterone gel rubbed on the arms and shoulders could cut heart-disease risk up to 30 percent for middle-aged men whose levels of the hormone are abnormally low, a study suggests.
The gel, however, may increase the risk of prostate cancer and it won't work in the 90 percent of middle-aged men whose testosterone levels are normal, said the study's author, Dr. Per Bjorntorp of the University of Gothenburg in Sweden.
''I've had hundreds of colleagues calling from all over Europe with the intent to start treatment like this, but I have strongly recommended that they not do it, because we don't know enough about the risks with the prostate yet,'' Bjorntorp said in a telephone interview Monday.
In a study appearing in the current issue of the journal Obesity Research, Bjorntorp and his colleagues showed that diabetes risk, blood pressure and cholesterol all dropped in the men whose testosterone levels were restored to normal with applications of the gel.
The men also experienced a slight reduction in weight. ''The weight decrease is not particularly impressive,'' Bjorntorp said. ''This is not a slimming drug, or anything like this. Also, we have signs of increased muscle strength and increased energy.''
Bjorntorp said that perhaps as many as 10 percent of middle-aged men have low testosterone levels. The others are not candidates for the gel. ''In men with normal testosterone levels, it's not active,'' he said.
Dr. Ahmed Kissebah, an obesity expert at the Medical College of Wisconsin in Milwaukee, said that testosterone treatment would not replace the traditional prescription of dieting and exercise to reduce heart-disease risk.
''You're not going to treat this by testosterone or a miracle drug. If this could be an addition, good.''
In the study, 31 men overweight men over age 40 were divided into three groups. One was given the gel. Another was given a related form of testosterone, called dihydrotestosterone. The third was given a placebo gel containing no hormones.
Only the testosterone gel had any effect, Bjorntorp said.