al., 1983). Both estrogen therapy and androgen therapy have been shown to have some effect on the restoration of sexual behavior after surgical ovariectomy (Lieblum et al., 1983; Sherwin et al., 1985). Estrogen replacement in ovariectomized female monkeys has been shown to increase female initiation of sexual behavior (Zehr et al., 1998). At menopause, when there is a naturally occurring decrease in reproductive hormone levels (both estrogens and androgens), a decrease in sexual desire has been generally reported (McCoy and Davidson, 1985). There have been several reports of a general correlation between androgen levels and sexual interest in post-menopausal women (Lieblum et al., 1983; McCoy and Davidson, 1985), but these studies have not determined whether fluctuations in androgen levels in individuals correlate with changes in sexual interest. Estrogen treatment can also lead to an increase in sexual activity in postmenopausal women, but it is difficult to determine if this is an action at the level of the brain or is secondary to increased comfort with intercourse due to increased lubrication of the vagina (Sherwin, 1991). Studies looking for correlations in premenopausal females with circulating levels of androgens and estrogens have been somewhat confusing.
In macaques there is a clear increase in sexual behavior in midcycle (Goy, 1979; Wallen, 1990). Although this could be due to an increase in attractiveness of females to males as estrogen levels rise (Czaja et al., 1977), there is evidence that, when the male’s mobility is limited and the female can control proximity, there is a cyclic increase in the female’s approach to males (Czaja and Bielert, 1975; Pomerantz and Goy, 1983), and females will work harder on an operant task to gain access to males at midcycle (Bonsall et al., 1978). However, whether these cyclic changes in sexual interest are governed by estrogens or androgens is difficult to determine because they rise in concert, androgens being a precursor to the ovarian synthesis of estrogen. A study by Zehr et al. (1998) showing that estrogen replacement alone to ovariectomized female monkeys can stimulate female sexual initiation and earlier studies showing that in the normal menstrual cycle changes in circulating estradiol but not androgen correlate with changes in female sexual initiation (Wallen et al., 1986) support a role for estrogen in governing female sexual behavior.
Several studies in ovariectomized, estrogen-treated monkeys have suggested that adrenal androgens may play a role in modulating female sexual behavior (Baum et al., 1977; Everitt et al., 1972), but such an effect has not been seen in ovary-intact macaques (Lovejoy and Wallen, 1990). Moreover, Wallen et al. (1986) found that ovarian suppression eliminated female sexual initiation, even though the adrenals were intact and functioning. As reviewed by Wallen (2001), hormonal influences on women’s sexuality have been difficult to demonstrate and to interpret due to unwillingness of subjects to be sampled either physiologically or behaviorally and strong