The efficacy and safety of testosterone treatment for hypoactive sexual desire disorder in postmenopausal women not receiving estrogen therapy are unknown.

We conducted a double-blind, placebo-controlled, 52-week trial in which 814 women with hypoactive sexual desire disorder were randomly assigned to receive a patch delivering 150 or 300 μg of testosterone per day or placebo. Efficacy was measured to week 24; safety was evaluated over a period of 52 weeks, with a subgroup of participants followed for an additional year. The primary end point was the change from baseline to week 24 in the 4-week frequency of satisfying sexual episodes.

At 24 weeks, the increase in the 4-week frequency of satisfying sexual episodes was significantly greater in the group receiving 300 μg of testosterone per day than in the placebo group (an increase of 2.1 episodes vs. 0.7, P<0.001) but not in the group receiving 150 μg per day (1.2 episodes, P=0.11). As compared with placebo, both doses of testosterone were associated with significant increases in desire (300 μg per day, P<0.001; 150 μg per day, P=0.04) and decreases in distress (300 μg per day, P<0.001; 150 μg per day, P=0.04). The rate of androgenic adverse events — primarily unwanted hair growth — was higher in the group receiving 300 μg of testosterone per day than in the placebo group (30.0% vs. 23.1%). Breast cancer was diagnosed in four women who received testosterone (as compared with none who received placebo); one of the four received the diagnosis in the first 4 months of the study period, and one, in retrospect, had symptoms before undergoing randomization.

In postmenopausal women not receiving estrogen therapy, treatment with a patch delivering 300 μg of testosterone per day resulted in a modest but meaningful improvement in sexual function. The long-term effects of testosterone, including effects on the breast, remain uncertain. (ClinicalTrials.gov number, NCT00131495.)