NORFOLK, Va. — Doctors have begun a clinical trial on a female testosterone gel they hope can help menopausal women who have lost interest in sex.

The treatment, called LibiGel, is one of the first therapies geared toward women with low libidos, as opposed to men (think Viagra and Cialis). Patients apply the gel once a day to skin on their upper arm, delivering testosterone through the skin and into the bloodstream.

“There is a real unmet need here,” said Dr. Frank Morgan, an OB/GYN with Tidewater Physicians for Women, a practice involved in the nationwide study.

An estimated 40 million women suffer from some type of sexual disorder, according to a study published in the Journal of the American Medical Association. The most common is a lack of sexual desire, which can harm a woman's relationships as well as her physical and mental health.

While many things can lead to loss of libido, a low level of testosterone often is to blame. Since the ovaries produce the hormone, a woman's interest in sex may drop after she goes through menopause or has her ovaries removed.