Estrogen Replacement Therapy (ERT) is therapy to replace estrogen no longer made by a woman's body because she is post-menopausal or her ovaries have been damaged or removed.
For many women, the amount of estrogen produced by the ovaries decreases around the ages of 45 and 50. This decline, which is not noticed by most women, goes on for several years. As women become older, the decline in estrogen levels becomes greater. This drop eventually causes the menstrual period to become less frequent and then stop. Menopause occurs when a woman no longer has her period.
The decreased level of estrogen may also be responsible for the uncomfortable symptoms of menopause. Women may experience hot flashes, mood swings or depression, and a decline in vaginal lubrication. The symptoms vary from woman to woman; some have no unpleasant effects while others find them very severe and require medical attention.
Osteoporosis (or bone loss) is another effect of reduced estrogen levels after menopause. Estrogen, calcium and exercise are needed to build and maintain bone. In women, bone density increases until ages 30 to 35. The loss of bone mass increases after menopause. Bone slowly loses calcium and becomes more brittle. As a result, a woman in her older years is more likely to have bone fractures.
The benefits and risks of long-term estrogen use should be weighed and discussed by each patient and her physician. About 10 percent of all women receiving ERT experience minor side effects. These may include swollen breasts, nausea, headaches, fluid retention and weight gain. A small percentage of women may show an increase in blood pressure while on ERT.
In general, women who have had breast cancer should not take estrogen replacement. Those who have migraine headaches, diabetes, asthma, and a history of blood clots or active liver disease, may also be advised not to undergo ERT. These can often be controlled, however, in patients taking estrogens. The major benefits are preventing osteoporosis and heart disease.
Women taking estrogen should follow instructions carefully and must be checked regularly by a physician. The doctor should be notified about any unexpected vaginal bleeding. Not all women consider the benefits of ERT worth the risks. Eating a balanced diet with enough calcium, getting exercise and not smoking cigarettes can reduce the rate of bone loss.
Estrogen and Risk of Cancer of the Uterus
The use of oral estrogen alone (without the use of oral progestin for part of the cycle, or when used without periodic interruption) has been shown to be associated with the development of cancer of the uterine lining. Used commonly in past decades, this practice has now been essentially replaced with newer, safer methods of estrogen administration.
Estrogen and Risk of Breast Cancer
Research results are conflicting as to whether or not women who use estrogen replacements have a higher risk of breast cancer than those who never used estrogen or those who once used estrogen and have discontinued. Recently, a large study, overseen by the Women’s Health Initiative, focused on the effects of long-term HRT consisting of combination estrogen/progestin. The study found an increased risk of breast cancer in patients taking long-term HRT compared to women not using HRT for five years or more.
Estrogen and Heart Disease
The Women's Health Initiative Study also found that long-term HRT was associated with a higher risk of heart disease, thromboembolism and stroke. This contradicts previous research that suggested a decreased risk or no effect.
Hormone Replacement After Hysterectomy
If you have had a hysterectomy (and are therefore not at risk for uterine cancer) your doctor might prescribe estrogen, which can be taken by pill, patch or cream. Unlike progestin, taking estrogen does not result in a return of monthly periods.
Estrogen tablets (Premarin) are the most commonly prescribed form. The recommended dose is 0.625 mg. Another form of estrogen, ethinyl estradiol, is widely used in Europe and has been prescribed for some American women who have experienced problems with other forms of estrogen. The standard dose is 1 mg. The increased risk of breast cancer is well described in women taking estradiol.
The transdermal patch (Estraderm) delivers estrogen through the skin and is considered safer for women at risk of liver disease or high blood pressure because it bypasses the liver. The patch is affixed to the abdomen, thigh or buttock and is changed twice weekly. Estrogen creams (Premarin) are topical creams for treating vaginal dryness.
Premarin is widely used. The drug, derived from the urine of pregnant mares, is the number one form of estrogen used in hormone replacement therapy. A generic form of Premarin is under development, but there remains a lingering uncertainty about bioequivalency. Many women's advocates believe that generic conjugated estrogens should be made available as a less costly alternative to Premarin.
Need for Individual Therapy
Although the evidence suggests that postmenopausal estrogen may increase risk for some diseases, current data on estrogen's effects argue for an approach in which this hormone's potential risks and benefits are weighed for each woman on an individual basis. When HRT therapy is felt to be necessary, the current recommendation is to initiate therapy with low doses and for as brief a time period as possible.
Those most likely to gain from estrogen-replacement therapy are women who are particularly bothered by symptoms (such as hot flashes) or who are more likely to develop osteoporosis because of certain risk factors - those who have a slim frame, experienced menopause early, are sedentary, or use alcohol or tobacco.
If a woman has undergone a hysterectomy, she is no longer at risk for cancer of the uterus; therefore, hormone-replacement therapy can consist of estrogen alone (without the addition of a progestrogen). The issue of whether or not to initiate therapy is more complicated for a woman whose uterus is still intact. In general, such women are given a combination of estrogen and a progestrogen to avoid increasing their risk for uterine cancer. Many experts recommend periodic biopsies of the uterine lining (endometrium) in this group, so that any evidence of malignancy can be detected early.
The disadvantages and benefits of estrogen therapy must be determined by each woman after discussion with her physician.