A lifetime of health differences: gender, hormones, and health

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A lifetime of health differences: gender, hormones, and health

by Ruth Schechter on Sunday, September 19, 2010 - 11:45pm

Marcia StefanickUnderstanding the differences in men’s and women’s physical and mental health is changing dramatically because of research in identifying lifelong patterns of disease. Tracking sex differences in human disease—from shortly after fertilization through childhood, puberty, adulthood, and old age—is providing insights into health issues specific to women, as well as men.

“It is amazing what happens before we are even aware if the fetus is a boy or a girl,” says Marcia Stefanick, PhD, a professor of medicine in the Stanford Prevention Research Center and a Clayman Institute faculty research fellow. “Sex hormones produce significant and irreversible differences in brain structure and function. The sexes are fundamentally different—and that is established long before birth.”

Stefanick chairs the national steering and executive committees for the NIH-funded Women’s Health Initiative, a large-scale study that dashed long-held beliefs that menopausal hormone therapy offered protection against heart disease in addition to its intended use of relieving postmenopausal symptoms. Negative findings for the combination of estrogen and progestin, in particular, were so apparent that this part of the study was stopped about three years early.

The researchers found that postmenopausal women who take combination hormone therapy double their risk of breast cancer—establishing a clear link between hormone use and breast cancer. Menopausal estrogen, alone or with progestin, increases the risk of stroke, though it also reduces the risk of hip fracture, particularly in women 65 and over. The risk of dementia, however, is also increased by estrogen use in this age group.

Stefanick is now eager to identify sex and gender-related gaps in research on the development, diagnosis, and treatment of specific diseases and health outcomes throughout the life cycle, including chromosomal and hormonal influences on growth and development, disorders influenced by metabolism (such as osteoporosis and menopause), and diseases like cancer and cardiovascular disorders.

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“For years, women’s health had been defined primarily as reproductive health. Women were not routinely included in most major medical research studies, and scientists rarely considered biological sex as a variable in their research,” says Stefanick. “But it is apparent that there are clear differences in incidence and manifestation of disease based on sex. Almost every system is affected by estrogen and testosterone—heart, bone, brain, cancer.”

For example, coronary heart disease affects women approximately 10 years later than it does men. Studies have shown that a woman is twice as likely to die within the first 60 days, and female heart attack survivors have a much higher rate of a second incident. This statistic is based not only on biological differences but is also affected by “gendered medicine”—differential medical treatment of men and women, says Stefanick.

In addition, differences in the symptoms of a heart attack—men report primarily chest pain, whereas women report symptoms that include indigestion, fatigue, and pain radiating in other areas of the body—result in less immediate recognition of a woman’s heart attack by both the patient and the medical professional. Certain risk factors also differ: While diabetes can double a man’s risk for heart disease, the disease increases a woman’s risk as much as four times.

Anatomically, women’s hearts, arteries, and blood vessels are smaller than men’s, so it may take less plaque to block their vessels; there also may be differences in how plaque is distributed, says Stefanick, thus requiring different therapeutic choices. iStock_000008654096Small.female-male“There is a real discrepancy in mortality rates between the sexes,” Stefanick says. “We are just beginning to scratch the surface in understanding these differences in terms of health, disease, and treatment over the life span. Some differences arise from simple physiology, but there are many social factors as well. More research on sex differences will get us to the real basic biology of better health for males and females.”