Testosterone, the male sex hormone, boosts sexual desire and activities in postmenopausal women, according to a recent study.   But a small review published earlier said the effect of the male hormone therapy on the risk of breast cancer remains uncertain.

Off-label use of testosterone is allowed in the United States although the FDA has not approved this treatment for low sexual function or hypoactive sexual desire disorder particularly in postmenopausal women who experience surgery induced menopause.

The review titled "breast cancer risk in postmenopausal women using testosterone in combination with hormone replacement therapy" was conducted by Bitzer JJ and colleagues of University-Women's Hospital Basel in Basel, Switzerland and published in March 2008 in the journal Maturitas.

The authors searched records in Medline from 1969 through July 2007 and MEBASE and Biosis from 1990 through July 2007 for original reports in English and French.   They found no prospective randomized clinical trials were ever conducted to evaluate the risk of breast cancer from the testosterone treatment.

They found only five studies (two case-control studies, two cohort studies and one retrospective observational study), but the results were inconsistent. The researchers said all studies had severe methodological limitations and formulations and dosages used were not optimal.

They conclude that "at present, there are no valid randomized or observational clinical studies that provide evidence that the addition of testosterone to conventional postmenopausal hormone therapy influences breast cancer risk."

One recent trial conducted by Susan Davis of Monash University in Melbourne, Australia and colleagues showed that use of testosterone patches made by Procter & Gamble for 24 weeks more than doubled monthly sexual episodes at a high dose in women with low sexual desire and activities.

But in the one year trial, published in the November 2008 issue of the New England Journal, breast cancer was diagnosed in four of the 534 postmenopausal women treated with the male hormone compared to none in the 277 placebo recipients.