There's new evidence that women may be able to safely improve their love lives--by taking the principal male sex hormone, testosterone.Studies indicate that a lot of women have problems with their love lives -- a Harvard study involving more than 31,000 women in this month's issue of the journal Obstetrics and Gynecology, for example, found that 40 percent of women have sexual problems.

Previous studies have suggested that testosterone can boost a woman's libido and help make sex more pleasurable. But most of those studies also involved giving women the hormones estrogen and progestin as well and did not follow women for long periods to see if the treatment was safe.

In the new study, published in today's New England Journal of Medicine, Susan Davis of Monash University in Australia asked 814 postmenopausal women with low sex drives to wear a patch that delivered either one of two doses of testosterone or a placebo for a year.

After six months, the women who were getting the testosterone reported a big improvement in their sex lives. Either dose of testosterone significantly increased the women's sex drive, and those getting the higher doses reported a big increase in the frequency of "satisfying sexual episodes" each month -- from about two a month before the treatment to more than four. They also reported more orgasms and pleasure.

There were some downsides. One third of those getting the high dose of testosterone reported the growth of body hair (compared to 23 percent of those on placebo). And even more worrisome, four women were diagnosed with breast cancer, compared to none of those who recived placebo. Researchers say it's unclear whether that had anything to do with the testosterone.

In an editorial accompanying the study, which was sponsored by testosterone patch maker Proctor & Gamble, Julie Heiman of the Kinsey Institute for Sex, Gender and Reproduction at Indiana University said that while the new study provides encouraging new data that testosterone can help women improve their sex lives, more research is needed to make sure it doesn't come at the cost of more breast cancers.