TUESDAY, June 27 (HealthDay News) -- Three new studies suggest that testosterone can be of real help, and potential harm, to women.

Women do have natural, low levels of these "male hormones," and improving deficiencies by using a testosterone patch can boost mood and sexual health, two studies found.

But a third study found that high levels of testosterone can also triple heart risks for older women.

Taken together, the findings underline the fact that "we don't know what really is considered to be a normal or beneficial testosterone level at this point," said Dr. Anne R. Cappola, an assistant professor of medicine and epidemiology at the University of Pennsylvania, and lead researcher on the heart-risk study.

The studies were presented Monday at the annual meeting of the Endocrine Society, in Boston.

Testosterone is usually thought of as a male hormone, but women have it, too. For women with androgen (male hormone) deficiency, supplemental testosterone can improve mood, sexual function and quality of life, researchers from Massachusetts General Hospital in Boston reported.

"We thought of testosterone as being a male hormone and estrogen a female hormone," said lead researcher Dr. Karen Miller, an endocrinologist and assistant professor of medicine at Harvard Medical School in Boston. "But we are learning more and more that things are not as simple as that," she said.

In their study, Miller's team randomly assigned 51 premenopausal women with below-normal or undetectable levels of testosterone to either a placebo or Proctor & Gamble's testosterone patch, Intrinsa, which has not yet received U.S. Food and Drug Administration approval for use by American women.

During the one-year trial, women on the testosterone patch showed improvements in mood, sexual function and quality of life. There was, however, no change in cognitive function, they reported.

"Bringing testosterone levels up to normal, when there are low levels due to a pituitary problem, improves mood and sexual function. There were also improvements in quality of life, including energy level," Miller said.

She cautioned that the study did not deal with women with normal testosterone levels. "Our concern is that supplemental testosterone in women with normal levels would have side effects, like unwanted facial and body hair," she said.

The data are very preliminary, Miller added. "There is no Food and Drug Administration testosterone patch approved for women," she said.

In a second study -- this time by researchers at Monash University in Melbourne, Australia -- investigators gave either the 150 gram/day or 300 gram/day versions of the Intrinsa patch, or a placebo, twice a week to 771 postmenopausal women.

Six months into the study, women on the 300 gram/day patch reported "significantly improved" levels of sexual activity, desire, and other markers of sexual function, as well as lowered anxiety, compared with women taking placebo. Women on the lower-dose (150 grams/day) patch saw only minimal improvements in sexual function, the Australian team reported.

The researchers noted that women on higher-dose Intrinsa did experience "an increase of the frequency of unwanted hair," although this side effect was rated as "mild to moderate in severity." The study was funded by Proctor & Gamble.

Last December, the FDA voted against the approval of Intrinsa for women with low libido, citing insufficient long-term safety data. Thus far, the only such remedies available to women with low libido are off-label, including Estratest (estrogen and methyltestosterone), currently on the market for relief of menopausal symptoms, and some other products that are specifically made for men.

One expert said Miller's study is important, but cause-and-effect remains unclear. "This study adds to other studies that look at androgens in mood and sexual function," said Dr. Glenn D. Braunstein, the chairman of the department of medicine at Cedars-Sinai Medical Center, Los Angeles. "But it is not clear whether this effect is a direct effect of testosterone or one that is mediated through estrogen," he said.

"Women who have an organic cause of low testosterone, and you give them back testosterone -- you get improvement in mood and sexual function. But I don't think you can extrapolate this beyond the type of women in the study. Studies have to be done in women who have low testosterone from other causes," said Braunstein, who has served as a consultant for Proctor & Gamble and was principal investigator on the original Intrinsa trials.

In the third presentation, Cappola's group reported that high testosterone levels in older women are a predictor of cardiovascular disease.

"Older women that have higher testosterone levels, for older women, are more likely to have cardiovascular disease than those who have lower levels," the Philadelphia researcher said.

In this study, Cappola and colleagues measured testosterone levels in 344 women, aged 65 to 98 years. They found that women who had the highest testosterone levels were three times more likely to have heart disease compared with women who had lower testosterone levels.

However, they also found that women with the lowest testosterone levels were also at a higher risk of heart disease compared with women who had testosterone levels in the midrange.

Because another hormone, insulin, has long been tied to cardiovascular risk, the researchers adjusted their findings to take insulin resistance into account. This greatly reduced the association between high testosterone and heart disease, they said.

Cappola believes that women who have high testosterone levels have had them throughout their lives. "But we can't tell whether testosterone is a marker or actually causing the cardiovascular disease," she said. "Insulin resistance may be a part of this, but it doesn't explain everything," she added.

There is nothing to do about this right now, Cappola said. "We don't have good ways, in postmenopausal women, of lowering testosterone levels anyway," she said.

One expert agreed that the findings don't have any implications for treatment right now.

"This study shows the complexity of hormones in the aging population," said Dr. Robert Vigersky, from the Walter Reed Army Medical Center. "However, trying to change testosterone levels in older women is something that is not supported by any of this data," he said.

Vigersky noted that risk of heart disease was seen with both high and low testosterone levels. "What this means diagnostically and interventionally is not clear," he said. "There isn't anything that anyone can take from this from a treatment standpoint," he added.

More information

For more on women and testosterone, head to the Jean Hailes Foundation.