"Estrogen is a mood elevator, it works in the brain to maintain interest in sex, but it also works at the level of the genitals, helping to increase sensation and just making sex more pleasurable," says Corio.
Without it, she says, not only can desire take a dive, vaginal tissue begins to dry and shrink. As a result, intercourse can become uncomfortable, or even painful. Problems with desire, say experts, are easy to understand.
"Who wants to make love when making love hurts?" asks Goldstein.
Moreover, he says, avoiding sex because of pain only leads to more pain. The old "use or lose it" theory really does apply.
"From a strictly physical standpoint, the less sex you have the more painful it is when you try to have it," he says.
Put the Sizzle in Sex
While estrogen levels are important, the latest research shows that the male hormone testosterone also plays a role in a woman's sex drive. Though present in only tiny amounts, some doctors say it's the seasoning that makes her sex drive sizzle.
Moreover, when levels become erratic, as they do at midlife, that sizzle can fizzle fast.
"There are a lot of physical reasons a woman can experience a decrease in sexual desire. But for many women who are otherwise healthy, a drop in testosterone that occurs at midlife is the reason," says Braunstein, who is one of the nation's leading researchers on testosterone treatment in women.
Complicating matters further, studies show that sometimes the very treatments women take to control midlife symptoms -- such as HRT or low-dose birth control pills -- can actually disrupt desire by robbing the body of testosterone.
"When these hormones are taken orally, they are metabolized by the liver, which in turn puts out a protein that binds to testosterone, causing a deficiency," says Braunstein. This, he says, can also be true for younger women using birth control pills for contraception.
And while in younger women the answer may be to simply switch brands of birth control pills, in women over 40, Braunstein says, adding tiny amounts of testosterone back into the body is the solution.
But not everyone agrees. Goldstein says the jury is still out on whether it really can help or even if it's safe. And the FDA advisory panel ruled that the testosterone patch for women needed more safety data before approval is granted.
Still, many doctors do prescribe testosterone "off label" -- frequently turning to drugs like Estratest, a combination estrogen-testosterone prescription approved for hot flashes and other menopause symptoms. But if you're at all worried about taking estrogen, experts say this is not the drug for you.
Finding Your Mojo Again
Admittedly, there are far more options for men seeking to rediscover their libido than there are for women trying to find theirs. In fact, despite rumors -- and even some early clinical evidence -- that Viagra can encourage both genders to jump in the van and head for the all-night love fest, studies show it had disappointing results in