Brian Palmer, a recent graduate of Mayo Medical School, says he was taught mainly about the male body in his anatomy class. His experience reveals much about the way many women are treated by their doctors.
"We were going through the abdomen and, at the time, [the professor] explained male genitalia as the extension of the abdomen," said Palmer, who is also president of the American Medical Student Association. "And one of the female students raised her hand and asked, 'Are we ever going to learn female anatomy?' "
Palmer says the topic was eventually covered, but women's sex organs were described almost as add-ons.
The field of gender-specific medicine looks at how disease progresses differently in women and men.
"Women are more than just boobs and tubes," said Dr. Marianne Legato, chairwoman of the Partnership for Gender-Specific Medicine at Columbia University. "In fact, we're different in every organ system of the body, including the brain, the heart, the gut -- even our skin is different from that of men in important ways."
Gender-Based Medical Differences
The female brain, according to research, has more intercellular connections, which may be why women are twice as likely to recover the ability to speak after a stroke. The male brain has more depression-fighting serotonin, which helps explain why men are far less likely to suffer depression.
Smoking damages a specific gene in women, making female smokers far more likely to get lung cancer, while female hormones help protect women from pancreatic cancer. Bile has a different composition in women, as well, making them far more likely to have gallstones.
Researchers in gender-specific medicine say their discoveries are revolutionizing health care. Upon learning that many drugs work differently in women, doctors were able to improve treatments for heart disease, diabetes and HIV.
Dr. Mary Young hopes her groundbreaking research at Georgetown's Center for the Study of Sex Differences could one day extend the lives of HIV-positive women.
"Early in the disease ... [the] virus causes more harm in women's bodies than in men's bodies," she said.
Young says HIV-positive women should get medication at an earlier stage than men, but many doctors are unaware of that.
There is such resistance to gender-specific medicine, Legato says, that when she lectures, many male doctors leave the room.
"Many physicians insist that one-size medicine fits all," she said. "Many of them think that the whole idea of gender-specific medicine is nonsense."
But increasingly, hard science is proving them wrong by showing that gender is much more than just an add-on.
ABC News' Jessica Yellin filed this report for "World News Tonight."