Diagnosis: Female

By Alice Park

Medical science is learning that sex does make a difference. Men's and women's bodies each have their own health problems, react differently to drugs and often require different treatments. We bring you some of the latest thinking:

IMMUNE COMPLEXITY

A woman's immune system displays an exquisite amount of control that a man's cannot replicate. It's still not clear why, but the female body's defenses tend to mount more aggressive responses to invading marauders; then, during pregnancy, this response is dampened considerably to accommodate the fetus. Perhaps owing to this on-off intensity, women are more prone to developing lupus, rheumatoid arthritis and multiple sclerosis, all conditions in which the immune system attacks healthy tissue. Researchers are just beginning to study why estrogen might cause the defense system to rev into overdrive in these cases.

HABITS OF THE HEART

The classic chest-crushing pain that is the hallmark of a heart attack turns out to be mainly a male symptom. Women's heart attacks, by contrast, tend to show up as shortness of breath, fatigue and jaw pain, stretched out over hours rather than minutes.

Women tend to suffer their first heart attack 10 years older than men. Yet, partly because the women are older, those heart attacks are more often fatal. This is a postmenopausal phenomenon, a trade-off for years of protection from estrogen. Staying bathed in the hormone keeps blood vessels elastic and free of hardened-plaque formations. Estrogen also instructs the liver to churn out more HDL, or good cholesterol, which pulls plaque away from artery walls.

Drugs commonly used to break up clots and stabilize erratic heartbeats are less effective in women than in men. Hormone-replacement therapy-estrogen and progestin-has been shown to help. A U.S.-government study is currently under way that aims to clarify how estrogen works on the heart, brain and breast.

REPRODUCTIVE ORGANS

Advances in diagnostic exams and hormone treatments have drastically cut the incidence of cancer of the uterus, ovaries and cervix over the past five decades. Pap smears that detect abnormal cells in the cervix before they become malignant have contributed to a 75% drop in cervical cancer since the 1950s. Wider use of birth control pills and hormonereplacement therapy (with estrogen and progestin) have decreased the risk of ovarian and uterine cancers. Recent research also suggests that in some cases, a low-fat diet can cut the risk of cervical cancer even further.

RISKS TO THE KNEE

As women participate in more and more sports, orthopedists are noticing a difference in the types of injuries women are prone to. They appear to be more susceptible than men to damaging the ligaments that hold the knee together. Many women basketball players have suffered painful and potentially debilitating tears to the anterior cruciate ligament, which can take months to heal. Doctors think it may have something to do with a woman's wider hips, which place a greater strain on the ligaments joining the thigh to the knee. These ligaments are weaker in women to start with.

SLOWER METABOLISM

Women tend to metabolize a number of drugs differently from men:

--ALCOHOL: It takes fewer drinks for a woman to feel the effects, because the liver breaks down alcohol more slowly, leaving more of it floating in the blood.

--ASPIRIN: The painkiller takes longer to clear a woman's system. Because it keeps platelets from clotting, aspirin should be avoided by pregnant women. It can trigger bleeding in the fetal brain.

--BETA-BLOCKERS: Because drugs like Inderal, prescribed to reduce blood pressure and migraine pain, take longer to metabolize in women than in men, the dosage must be more carefully monitored to avoid side effects.

--TRICYCLIC ANTIDEPRESSANTS: Women taking oral contraceptives may need lower doses of these drugs to treat their depression, since the Pill keeps levels of the drugs in the body high.

MIND AND MOOD

Women are more prone to depression than men, and the reason may have as much to do with biology as it has with stress and other life-style factors. Evidence is mounting that the male and female brains may respond differently to hormones and brain chemicals. Women produce less serotonin, a mood-regulating chemical, than men, and are more sensitive to changes in serotonin levels, which are in turn regulated by estrogen. Women thus respond better to drugs affecting the serotonin system (such as Prozac), while men tend to respond better to drugs that also affect norepinephrine, a neurotransmitter secreted by the adrenal glands and by nerve endings during stress.

Estrogen may stave off the dementia and memory loss of Alzheimer's disease by actually encouraging neurons in the brain to grow new nerve extensions. Postmenopausal women who do not have hormone-replacement therapy have a greater chance of developing Alzheimer's and memory loss than men of the same age, whose testosterone is metabolized into estradiol, a form of estrogen.

BREAST CANCER

Much of the current research is focusing on early detection. Studies show that women with a mutation in either gene BRCA1 or gene BRCA2 have as much as a 56% chance of developing breast cancer by age 70. The predictive power of the genes, however, is still being debated, as scientists try to determine how genes, environment and other factors affect the appearance and growth of tumors.

Treatment options are constantly expanding, thanks to a better understanding of how best to combine surgery, drugs, chemotherapy and radiation. New forms of estrogen-like supplements, initially developed to prevent osteoporosis, appear to prevent the growth of breast tumors as well, and more comprehensive studies show that an old drug, tamoxifen, can cut the risk of cancer as much as 45% over four years.

DIGESTIVE SYSTEM

Even if a man and a woman eat the same thing, it may take the woman much longer to digest it. That leaves women three times as vulnerable to chronic constipation as men and twice as likely to develop intestinal disorders. The sex discrepancy apparently starts with chewing: preliminary studies show that female saliva differs chemically from that of men, perhaps setting the stage for food's slower journey through a woman's digestive system.

CANCER TYPES

Projected number of deaths in 1999

WOMEN

1 Lung & bronchus 68,000 2 Breast 43,300 3 Colon & rectum 28,800 4 Pancreas 14,700 5 Ovary 14,500

MEN

1 Lung & bronchus 90,900 2 Prostate 37,000 3 Colon & rectum 27,800 4 Pancreas 13,900 5 Non-Hodgkin's lymphoma 13,400

FEELING PAIN

Contrary to anecdotal stories, numerous studies have documented that women experience pain more acutely and more frequently than men, indicating that the sexes may detect and dampen pain differently. In a study of dental patients, women responded more favorably than men to a class of pain relievers known as kappa opioids, including pentazocine, suggesting that receptors for inhibiting pain may vary by sex. Moreover, women are less responsive than men to nonsteroidal anti-inflammatory drugs, such as ibuprofen.

BONE LOSS

Women, more than men, experience a significant change in their bones in later life. In postmenopausal women, the skeleton becomes less dense, full of perforations caused by osteoporosis. The reason for the difference: less estrogen after menopause. The hormone slows down bone loss and builds up bone as well. Women past menopause who have estrogen-replacement therapy can prevent as much as 75% of their bone degradation and cut their risk of a hip fracture 50%.