Hormones like testosterone and estrogen do more than give men and women their characteristic shapes, or determine the placement of body hair. These and other hormones may also help to explain the different health risks that men and women face. Understanding the role sex hormones play in disease and wellness could be the key to successful treatment and prevention.
Heart disease remains the number one killer of both men and women throughout the world. After years of study, scientists recognize that both sexes experience similar risk levels for this disease. The difference is that women tend to develop heart problems later in life than men. Researchers believe that this could suggest a link between hormones and heart disease. Women typically develop cardiovascular conditions after menopause, when estrogen levels decline. Men, who naturally have lower estrogen levels, get the disease much earlier [source: Rosenfeld]. Researchers say this suggests that it may be possible to treat or prevent heart disease in both sexes using hormone-based therapies.
The same is true of autoimmune diseases, such as lupus or multiple sclerosis. Women represent a staggering 79 percent of patients with these autoimmune diseases, and scientists believe that hormones may be to blame. Estrogen, progesterone and other hormones may encourage the female immune system to overreact to certain types of stimuli, which explains why men, who have lower levels of these hormones, are less susceptible to the conditions. This theory is further supported by evidence that women who have autoimmune disorders often experience some relief from them during pregnancy or menstruation, when hormone levels typically fluctuate [source: Ohio State University].
Hormonal differences between the sexes also may explain the enormous disparity in breast cancer statistics. In 2001, more than 192,000 women developed breast cancer, and 40,200 died from the disease. That same year, only 1,500 men were diagnosed with breast cancer, and 400 died. Scientists believe that breast cancer risk is largely a factor of lifetime estrogen exposure [source: Warren et al]. Women naturally have high levels of estrogen, and those who use estrogen replacement therapy after menopause hits double their risks of breast cancer [source: Schechter]. Men with breast cancer often develop it because of an increase in estrogen or decrease in testosterone. This may be caused by obesity or by diseases of the liver or reproductive organs.
Although hormonal influences may seem impossible to counteract, learning more information on their effects also represents a source of hope. As doctors understand more about how diseases impact men and women differently, they can develop more effective methods of treatment based on the unique needs of each sex.
Sure, hormones are essential to the physical differences between the sexes. Different hormones of all sorts also might explain why we behave differently. On a daily basis, men produce about 20 times more testosterone than women [source: Mitchell]. Testosterone levels shoot up when a boy hits puberty, which leads to increased muscle mass, a lower voice, body and facial hair and a growth spurt. Testosterone also jump-starts a young man's libido by spurring the development of the scrotum, penis and prostate. Sperm production also kicks in during puberty. Testosterone often is associated with aggression, but studies have shown that removing it from humans doesn't necessarily lead to a drop in aggressive behavior [sources: Mitchell, University of Zurich].
Hormones are part of the physiological explanation about why men don't seem to shed a tear nearly as frequently as women do. The reason has nothing to do with testosterone, however. It appears that a woman's body has much more prolactin - - about 60 percent more - - than a man's body [source: Hoyt]. Prolactin is the hormone that causes a person to cry. The difference in crying between the sexes may have a few other causes. Men sweat more than women, so one theory proposes that men expel emotional toxins from the body by sweating, and women do so by shedding tears. In addition, a man's tear duct is smaller than a woman's. As a result, a woman can produce more tears than a man.
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