Gender differences Next, van Anders looked into the burning question of why men, on average, want sex more often than the average woman. Testosterone and womanly passions Testosterone also plays an important role in the competitive interactions of female mammals, including primates. She then compared low-versus-high testosterone participants and their self-reported levels of desire. But that idea is based on animal studies and studies of men who produce extreme, abnormally low levels of testosterone. What is more, their estradiol level increases when they "win" a contest with another woman that is actually manipulated by experimenters and remains elevated for a day. Often, the desire follows. It may seem strange, but the finding fits with previous evidence, van Anders said. Complicating the picture further, while high-testosterone women may be less interested in slipping between the sheets with a lover, high testosterone is linked to greater interest in masturbation in healthy women, according to research detailed online in May in the journal Archives of Sexual Behavior. Cortisol too high, too low, or rises and falls. Or your thyroid may start to sputter. Experiments have shown that testosterone administration increases self-rated genital sensitivity and objectively-measured sexual arousal in response to an erotic movie. Their other distinguishing features are that they tend to be physically attractive, to have tempestuous romantic lives, and to be highly competitive with other women what might be called the Marilyn Munroe effect. These two facts have led to the belief that testosterone is the reason for the desire, van Anders said. Cortisol, the main stress hormone, can start to climb and rob your other sex hormones. Things get a bit more complicated on the female side. In reality, desire is a lot like hunger, she said. Recent research is closing in on sex hormones androgens as well as estrogens playing a very similar role for women.