TESTOSTERONE AND SEXUAL FUNCTION
The prevalent dogma is that androgens regulate libido in women, although a woman’s sexual behavior is greatly affected by environmental, emotional, cultural and hormonal factors. The effects of androgens in the brain are mediated directly through the androgen receptor and through aromatization of testosterone to estradiol. Androgen receptors have been identified in the cortex, pituitary, hypothalamus, pre-optic region, thalamus, amygdala and brainstem.
Testosterone supplementation is associated with increased well-being, energy, appetite and
improved somatic and psychological scores in surgically menopausal women. For instance, in
one study of surgically menopausal women, supraphysiologic doses of testosterone enanthate
alone or in combination with estrogen, increased sexual desire, fantasies and arousal more than
estrogen alone.
In another study, testosterone and estradiol implants increased sexual activity, satisfaction, pleasure and frequency of orgasm more than estrogen implants alone. In a recent, well-designed, placebo-controlled, randomized clinical trial, women who underwent hysterectomy and oophorectomy and were on estrogen replacement were randomized to placebo patches or testosterone patches designed to nominally deliver 150 or 300 μg of testosterone daily for 12 weeks each. Although both dose-regimens of testosterone significantly increased serum testosterone levels, only the higher dose that increased mean serum free-testosterone levels into the upper end of the normal female range was associated with improvements in frequency of sexual activity, pleasure orgasm, sexual fantasies, masturbation and positive well-being.
Tutten et al reported that oral administration of testosterone undecanoate increased vaginal vasocongestion as measured by vaginal plethysmography during exposure to a potent visual stimulus in a small number of women with hypothalamic amenorrhea.
In a placebo-controlled, crossover study, daily administration of 50 mg DHEA daily for four months in women with adrenal insufficiency improved several aspects of sexual function and sense of well-being. It is unclear whether these effects were direct effects of DHEA on the brain or indirect effects due to the conversion of DHEA to testosterone. In contrast, a cross-sectional study did not show correlation between sexual function and gonadal steroids.
Thus, it appears likely that supraphysiologic doses of testosterone that increase serum testosterone levels above the physiologic range for healthy, young women may improve some aspects of sexual function in a subset of women with low androgen levels. However, we do not know whether physiologic replacement doses that increase serum testosterone levels into the midrange for young, menstruating women would produce meaningful improvements in sexual function and activity in healthy, older women with low testosterone levels.