Although we know that estrogens contribute to a general sense of well-being, help maintain the thickness and elasticity of the vaginal lining, and contribute to vaginal lubrication (Frank et al., 2008; Kingsberg, 2002), the role of estrogens in female sexual behavior is still unclear. Some researchers have reported that when postmenopausal women (menopause is associated with marked reduction in estrogen production) or women who have had their ovaries removed for medical reasons receive estrogen therapy (ET), they experience not only heightened vaginal lubrication but also somewhat increased sexual desire, pleasure, and orgasmic capacity (Dow et al., 1983; Kingsberg, 2002). The sexual benefits that often result from ET occur because estrogen provides "mood-mellowing" benefits and thus creates an emotional atmosphere receptive to sexual involvement (Crenshaw, 1996; Wilson, 2003). See Chapter 3 for a more detailed discussion of ET, including the link between ET and breast cancer.
Other investigators have found that ET has no discernible impact on sexual desire, and, when estrogen is administered in relatively high doses, it can even decrease libido (Frank et al., 2008; Levin, 2002). In view of these contradictory findings, the role of estrogens in female sexual motivation and functioning remains unclear.
There is less ambiguity about the role of testosterone in female sexuality. Considerable evidence indicates that testosterone plays an important role as a libido facilitating hormone in females (Davis et al., 2008; Tucker, 2004). Clear evidence exists that there is "a testosterone dependent component of women’s sexuality. . ." (Bancroft & Graham, 2011, p. 717). Numerous experimental evaluations of the effects of testosterone on female sexuality provide evidence of a causal relationship between levels of circulating testosterone and sexual desire, genital sensitivity, and frequency of sexual activity. For instance, many studies have shown that testosterone replacement therapy enhances sexual desire and arousal in postmenopausal women (Frank et al., 2008; Shah & Montoya, 2007).
Other investigations have found that women who received testosterone or estrogen — testosterone therapy after natural menopause or surgical removal of their ovaries (ovariectomy) experienced remarkably greater levels of sexual desire, sexual arousal, and sexual fantasies than women who received estrogen alone or no hormone therapy after surgery (Nusbaum et al., 2005; Tucker, 2004).
Most of the evidence indicating the importance of testosterone in female sexual functioning has come from studies of women with low levels of this hormone because of ovariectomy, adrenalectomy, or natural menopause. One study of considerable interest sought to determine the effects of supplemental testosterone on the physiological and subjective sexual arousal in a group of sexually functional women with normal hormone levels. The investigators found that sublingually administered testosterone (under-the-tongue tablets) caused a significant increase in genital responsiveness within a few hours and that there was a strong and significant association between the increase in genital arousal and subjective reports of "genital sensation" and "sexual lust" (Tuiten et al., 2000).
Other studies have found that when testosterone is administered to women with a history of low sex drive and inhibited sexual arousal, the reported frequencies of sexual fantasies, masturbation, and satisfying sexual interaction with a partner typically increase (Davis, 2008; Nappi et al., 2011). Furthermore, when researchers compared testosterone levels in a group of healthy, sexually functional women with levels in a group of women with a reported lifetime history of low sex drive, they found evidence linking low libido with reduced testosterone levels. Women in the low-libido group were found to have significantly lower levels of testosterone than those in the sexually functional group (Riley & Riley, 2000).