Testosterone is often cast as the manly hormone, the chemical bestower of virility and the reason for men's high sex drives. But new research turns this conventional wisdom on its head. In healthy men, it turns out, testosterone isn't linked to sexual desire at all. And in women, high testosterone is actually associated with less interest in sex with a partner.
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.
The findings are unique because most studies of sexual desire and hormones use either animal subjects or focus on people with abnormally low or high testosterone who come into clinics for treatment, said study researcher Sari van Anders, a behavioral neuroendocrinologist at the University of Michigan. Healthy individuals are rarely studied, van Anders told LiveScience.
"People have argued that sex research focuses too much on dysfunction and pharmaceutical treatment as opposed to questions like pleasure or relationships or stress," van Anders said. "There is a whole scope of factors that go unstudied." [ Busted! 6 Gender Myths in the Bedroom & Beyond ]
Delving into desire
When people do study factors such as stress and body image regarding people's sex lives, they rarely look at hormonal influences at the same time. That's what van Anders did differently. She recruited volunteers from university classes and community fliers to fill out questionnaires on their relationships, their stress and moods, and their own feelings about their bodies and sexuality. These questions were designed to get at factors that influence people's sex lives: How happy are you, generally? How stressed? Are you self-conscious about your body during sex?
The 196 volunteers (105 men and 91 women) also answered questions about how frequently they had partnered sex and masturbated, and how frequently they had the desire to masturbate or to have sex with a partner.
People tend to think of desire as a single phenomenon, but the desire to have sex may come from a different place than the desire to masturbate, van Anders said.
"When you're feeling sexual desire for a partner there might be other factors that play into that, for example, how you felt about that partner that day, how attracted you feel to that partner, how attractive you feel to that partner, your relationship and things like that," van Anders said. [ 6 Great Things Sex Can Do For You ]
Solitary desire, on the other hand, may be more internal and less influenced by social factors like relationship satisfaction, she said.
Testosterone and libido
Each study participant gave a saliva sample for hormonal analysis. Van Anders measured testosterone as well as cortisol, a hormone released in times of stress (a surefire libido-killer ).
She then compared low-versus-high testosterone participants and their self-reported levels of desire. In men, she found, levels of testosterone had nothing to do with how much guys thought about sex, solitary or partnered.
Multiple studies have found that men generally desire sex more frequently than women. And men also produce more testosterone than women. These two facts have led to the belief that testosterone is the reason for the desire, van Anders said. But that idea is based on animal studies and studies of men who produce extreme, abnormally low levels of testosterone. In men in the healthy range, an extra spurt of the "macho hormone" doesn't seem to influence interest in getting busy. [ Top 10 Aphrodisiacs ]
"In this regular, healthy range of testosterone, it's high enough that the variations aren't what's driving any changes," van Anders said. (There have been studies, though very few, showing similar results.)
Things get a bit more complicated on the female side. Women with higher testosterone reported less desire for partnered sex. It may seem strange, but the finding fits with previous evidence, van Anders said. For example, women in long-term relationships have been shown to have lower testosterone. It could be that their partner desire relates to a need to be close and connected as opposed to simply a need for pleasure, van Anders said.
Alternatively, higher testosterone might reflect higher stress in women. Testosterone is secreted by the adrenal glands, which go into overdrive during stressful times.
Solitary sexual desire, on the other hand, was higher in the higher-testosterone women, such that the 27 women in the study who reported no desire to masturbate at all had lower testosterone than the women who said they sometimes felt desire to masturbate. The finding bolsters the idea that desire for a partner is more influenced by social factors, van Anders said, while solitary desire is more innate.
Next, van Anders looked into the burning question of why men, on average, want sex more often than the average woman. Sure enough, she found that testosterone was not the culprit. Levels of this hormone did not explain the differences in desire between men and women.
The only factor that did link to gender differences was masturbation. Men masturbated more than women and reported more sexual desire (with a partner and solitary). Women masturbated less, and reported less desire.
There's no way to tell from this research whether the desire or the masturbation comes first. But there are intriguing hints that perhaps the difference in masturbation habits could explain the desire gap, van Anders said. Sex therapists often tell low-desire patients to try starting sex or masturbation even if they feel uninterested. Often, the desire follows.
Though female masturbation has become less taboo, it is still somewhat stigmatized compared to male masturbation, van Anders said. It's possible that women simply don't practice revving up their desires as much as men do.
"The idea is that if women don't feel comfortable with their genitals and masturbating, and if they don't think it's okay and refrain from doing it and don't express their desires, after a while, the desire might change as well," van Anders said.
The next step, van Anders said, is to get a better handle on the concept of desire, focusing on social factors and not just pharmaceutical fixes for low libidos. People often think that the desire comes first and drives people to seek out sexual pleasure, she said. In reality, desire is a lot like hunger, she said. You might eat because you're starving, or because you're bored, or because it's 6:30 p.m. and that's when you have dinner.
"When you're saying you desire sexuality with another person, what are you desiring and are people desiring different things sometimes?" van Anders said. "Are some people more desiring to be with their partner, to give their partner pleasure, to have a routine, or for their own pleasure?"
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