The impact of testosterone treatment on sexual dysfunction was first described in the 1950s in studies of postmenopausal women who received testosterone in combination with estrogen. Although sexual function was not a primary outcome of these trials, improved libido was self-reported by 23–42% of the subjects. Studies performed in the 1980s and 1990s further elucidated the role of testosterone therapy in female sexual behavior.
Another trial compared oral estrogens alone with the combination of estrogen and testosterone (esterified estrogens 1.25 mg and methyltestosterone 2.5 mg once/day) in 20 postmenopausal women taking estrogen at baseline. Objective sexual arousal was measured by using vaginal blood flow velocity and fingertip blood flow. This study did not find a significant impact of testosterone on either vaginal or fingertip blood flow velocity. However, a study of eight premenopausal women receiving a single dose of sublingual testosterone undeconate 0.5 mg in a double-blind, randomized, placebo-controlled, crossover design demonstrated increased vaginal blood flow, self-reported sensations and sexual lust on a visual analog scale within 5 hours of the testosterone dose. A small crossover trial in 10 postmenopausal women without sexual dysfunction demonstrated a benefit for methyltestosterone 5 mg on genital sexual response with increased vaginal blood flow 4.5 hours after the dose. However, the women did not report a subjective increase in sexual response with testosterone.
Testosterone has rarely been evaluated alone in postmenopausal women but has been investigated in several studies as an addition to estrogen therapy. Twenty postmenopausal women with menopausal or sexual symptoms unrelieved by estrogen were enrolled in a small, randomized, double-blind, parallel-group study to evaluate the effects of testosterone in addition to estrogen therapy. Participants were randomly assigned to either esterified estrogens 1.25 mg/day or estrogen plus methyltestosterone 2.5 mg/day for 8 weeks. The Sexual Activity and Libido Scale (11 questions) was completed weekly by each subject. This scale evaluates vaginal dryness, sexual desire, pain with intercourse, clitoral sensation, and sensitivity on a scale from 0–4; vaginal moisture, orgasm, sexual fantasy, sexual response in the last 24 hours as yes or no; and sexual intercourse as none, once, twice, 3 times, or 4 or more times/week. Sexual desire and clitoral sensation were significantly increased from baseline at 8 weeks in the testosterone group. The frequency of sexual activity was significantly increased at week 4; however, this increase was no longer observed at 8 weeks.
A longer (16-wk), double-blind, randomized, parallel-group study comparing esterified estrogens 1.25 mg/day (19 women) with estrogen plus methyltestosterone 2.5 mg/day (18 women) was conducted to determine effects on fat and muscle mass and muscle strength. Sexual function was evaluated as a secondary objective by using three self-report questionnaires. A significant change from baseline was noted on each scale in the estrogen-testosterone group. A significant increase for pleasure/orgasm was noted on the BISF-W and for interest in sex on the SIQ scale in the estrogen-testosterone group.
Sexual function was the primary outcome in one crossover study involving 50 women with surgically induced menopause who were randomly assigned to estradiol 2 mg/day or estradiol and testosterone undecanoate 40 mg/day. McCoy’s sex scale questionnaire, a 14-item scale evaluating the previous 30 days, was used to compare sexual function at baseline and after 6 months of treatment. No significant difference was found between treatment groups for lubrication, pain with intercourse, interest in sex, or sexual thoughts and fantasies.
Although significant improvement from baseline was noted in the testosterone group on: enjoyment, satisfaction with frequency of sexual activity, arousal, frequency and satisfaction of orgasm, and feeling of attractiveness to partner), only the domains of enjoyment, satisfaction with frequency, and interest in sex were significantly improved in the testosterone group compared with the other groups.
Women receiving the formulation with testosterone reported a significant increase in responsiveness, which was more than twice that of women taking estrogen alone. Sexual interest or desire and frequency of desire were also greater in the testosterone combination group, with an increase noted at 4 weeks of therapy and maintained throughout 16 weeks. This study further solidified the role of testosterone in increasing sexual motivation in women with lack of sexual interest or desire.
Testosterone Supplementation for Hypoactive Sexual Desire Disorder in Women
C. Brock Woodis, Pharm.D, Amber N. McLendon, Pharm.D., Andrew J. Muzyk, Pharm.D.
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