Menopause is the time in a woman’s life when menstruation ends. It is part of a biological process that begins, for most women, in their mid-thirties. During this time, the ovaries gradually produce lower levels of hormones—estrogen and progesterone.
Estrogen promotes the development of a woman’s breasts and uterus, controls the cycle of ovulation (when an ovary releases an egg into a fallopian tube), and affects many aspects of a woman’s physical and emotional health.
Progesterone controls menstruation and prepares the lining of the uterus to receive the fertilized egg.
“Natural” menopause begins when a woman has her last period, or stops menstruating, and is considered complete when menstruation has stopped for one year. This usually occurs between the ages of forty-five and fifty-five, with variations in timing from woman to woman. Women who undergo surgery to remove both ovaries (oophorectomy) experience “surgical” menopause—an immediate end to hormone production and menstruation.
During menopause, a woman may experience problems such as hot flashes, night sweats, sleeplessness, and vaginal dryness. In addition, some long-term conditions, such as osteoporosis and coronary heart disease, are more common in women in the years after menopause.
By the time the menopause transition is complete, hormone production has decreased significantly. Even though low levels of estrogen are produced by the adrenal glands after menopause, they are only about one-tenth of the level found in premenopausal women. Progesterone is nearly absent in menopausal women.
Why are hormones recommended after menopause?
Menopausal hormone use (hormone replacement therapy, HRT, or post menopausal hormone use) usually involves treatment with either estrogen alone or estrogen in combination with progesterone or progestin, a synthetic hormone with effects similar to those of progesterone.
Estrogen usage, with or without progestin, approximately doubles the estrogen level of a menopausal woman; however, even with hormone treatment, the estrogen and progesterone levels do not reach the natural levels of a premenopausal woman.
Doctors may recommend using hormones to counter some of the problems often associated with menopause or to prevent some long-term conditions that are more common in postmenopausal women, such as osteoporosis.
What are the health benefits of hormone use?
In order to study the benefits and risks of hormone use, researchers commonly conduct two types of human studies: clinical trials and observational studies. In clinical trials, the participants are given either hormones or placebos (look-alike pills that do not contain any medications) to determine the effect of the hormones on various conditions and diseases.
In observational studies, there is no intervention by the investigators; they compare the health status of women taking hormones to women not taking them. The strongest evidence for proving an association between menopausal hormones and a disease or condition comes from clinical trials.
Do the benefits of hormone use after menopause outweigh the risks?
The best evidence for the risks and benefits of postmenopausal hormone use comes from the Women’s Health Initiative (WHI), a large randomized clinical trial of over 16,000 healthy women ages fifty through seventy-nine, in which half of the participants took hormones and the other half took a placebo pill.
The trial, sponsored by the NIH, was halted early when, in July 2002, investigators reported that the overall risks of estrogen plus progestin, specifically “Prempro,” outweighed the benefits. The WHI found that use of this estrogen plus progestin pill increases the risk of breast cancer, heart disease, stroke, and blood clots.
The study also found that there were fewer cases of hip fractures and colon cancer among women using estrogen plus progestin than in those taking a placebo.
Findings from the WHI Memory Study (WHIMS) reported in May 2003, showed that in older women age sixty-five and above, use of estrogen plus progestin doubled the risk of developing dementia; these same women also did more poorly on cognitive function tests compared with those taking placebo.
Additionally, an analysis of the quality of life of a subgroup of WHI participants of the same age found no change in general health, vitality, mental health, depressive symptoms or sexual satisfaction associated with use of estrogen plus progestin.
The risks and benefits of estrogen alone are less clear. The study of women in the WHI taking estrogen alone is scheduled to continue until 2005, and the results of this trial will provide evidence for the associated health effects.
Studies have shown that long-term exposure of the uterus to estrogen alone increases a woman’s risk of endometrial cancer (cancer of the lining of the uterus).
By Alice M. Crawford, MD, PhD