Testosterone treatment may help rev up a woman's sex drive. Yet measuring blood levels of the sex hormone doesn’t help diagnose women who suffer from low libido.

Researchers compared self-reported sex drive with blood levels of testosterone and other male sex hormones in a randomly selected group of women. While testosterone treatment has been more thoroughly studied in men than in women, it has been used with some success in treating women with low libido.

However researchers found little correlation between testosterone levels in women and sexual drive.

They concluded that assessing male sex hormone, or androgen, levels in the blood is not an effective diagnostic tool for identifying low libido in women. The findings are reported in the July 6 issue of the Journal of the American Medical Association.

“It is not like measuring iron levels in the blood to diagnose anemia,” researcher Susan R. Davis, MD, PhD, tells WebMD. “Female sexual dysfunction is much more complicated. There are plenty of women with normal [sexual desire] who have low testosterone levels, as well as women with normal testosterone levels who have low sexual function.”

Read WebMD's "Testosterone Patch: Women's Answer to Viagra?"

Low Sex Drive: A Common Complaint

Although figures are hard to pin down, it is estimated that anywhere from 8 percent to 50 percent of women report having a low sex drive. The problem becomes more common as a woman ages, as well as when her ovaries are removed -- a source of the sex hormones.

A large number of factors contribute to lack of desire and arousal in women, but experts in the field of women's health have become increasingly interested in the role of testosterone and other male sex hormones in recent years.

Testosterone treatment does help some women reclaim their sex drive, but the value of measuring male sex hormone levels in the blood as a predictor of low sexual function has not been clear.

The study by Davis and colleagues from Monash Medical School in Victoria, Australia, included just more than 1,000 randomly selected women between the ages of 18 and 75. None had been diagnosed with medical conditions or taking medications that reduced sexual desire.

The women completed questionnaires designed to assess sexual desire and arousal. They also provided blood samples, in which testosterone and the steroids androstenedione and DHEA sulfate were measured. These steroids are blood precursors to testosterone.

Neither testosterone nor androstenedione levels were found to have a correlation with sexual desire, arousal, pleasure, ability to achieve an orgasm, or sexual self-image.

Women under the age of 45 who reported low desire, responsiveness, and arousal were three to six times as likely to have low levels of DHEA sulfate as older women with low sexual function. But Davis says that measuring DHEA is not a useful diagnostic tool because many women with normal sexual function also had low levels of the steroid hormone.

Read WebMD's "Why Women Lose Interest in Sex"

Just 1 of Many Factors

Renown women’s health expert and author Judith Reichman, MD, says she is not surprised that measuring blood levels of male sex hormones is of little diagnostic value.

Reichman is a gynecologist who practices at Cedar-Sinai Medical Center in Los Angeles. Her best-selling book I’m Not in the Mood addresses sex problems among women.

“I don’t think anybody really believed that a blood test alone could predict libido,” she tells WebMD. “All kinds of things can and do contribute to the problem, including medications, relationship issues, and stress. You can’t just look at one thing and say, ‘Ah ha, we’ve found it.’”

The FDA failed to approve a testosterone patch for the treatment of low libido late last year, but the hormone is nonetheless increasingly being prescribed to women who complain of low sex drive.

While it seems to help some women it isn’t a panacea, Reichman says.

“I don’t want women to get the idea that if they put on a testosterone patch or take a pill that they will feel like they did when they were 18,” she says. “It just isn’t that simple.”

In addition there may be a risk of the development of side effects associated with testosterone treatment including acne excess body hair and other masculinizing effects, and cholesterol abnormalities.

Read WebMD's "Prescriptions for Sexual Frustration"

By Salynn Boyles, reviewed by Brunilda Nazario, MD

SOURCES: Davis, S. Journal of the American Medical Association, July 6, 2005; vol 294: pp 91-96. Susan Davis, MD, PhD, Women’s Health Program, department of medicine, Monash Medical School, Alfred Hospital, Victoria, Australia. Judith Reichman, MD, gynecologist, Cedar Sinai Medical Center, Los Angeles; and author, I’m Not in the Mood.