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Selective Estrogen Receptors

Selective Estrogen Receptors

Alternate Names

  • designer estrogens
  • SERMs

Definition

Selective estrogen receptor modulators, or SERMs, are medications that act similarly to estrogen in some tissues of the body and block the effects of estrogen in others. The two most common SERMs used in the United States are raloxifene (i.e., Evista) and tamoxifen (i.e., Nolvadex).

What is the information for this topic?

How does estrogen affect the body? Estrogen is a female hormone. It is made by the ovaries from puberty to menopause. It acts on many different cells in the body such as the brain,the breasts, the bones, the heart and the uterus.
Estrogen is sometimes given to women after menopause to deal with the symptoms she may get from the normal decline in these hormone levels. However, estrogen can cause tissue growth in a woman's breast and uterine lining. If used for more than 5 to 10 years, it may slightly increase the risk of breast cancer.
It may also slightly increase the risk for uterine cancer in some women. Women who take estrogen and do not have their uterus are not at risk for uterine cancer. Women who still have their uterus and take estrogen should also take a progestin. This reduces the risk of uterine cancer to the level of women who do not take estrogen at all.
How does raloxifene affect the body?Raloxifene (i.e., Evista) has an estrogen-like effect on bone. It increases bone density and prevents fractures in the spine related to osteoporosis. It has been approved by the Food and Drug Administration, or FDA, for prevention and treatment of osteoporosis in women after menopause.
Raloxifene also has some positive effects on blood cholesterol. It can lower total cholesterol and LDL, which is also known as "lethal" or "bad" cholesterol. High total cholesterol and LDL cholesterol levels increase a woman's risk of coronary heart disease.
However, raloxifene does not raise HDL, also called the "healthy" or "good" cholesterol, or increase triglycerides like estrogen does. Whether raloxifene will protect women against heart disease is currently being studied.
There is some preliminary information to suggest that raloxifene may be useful in preventing breast cancer. It is not approved by the FDA for this use but is continuing to be studied. Raloxifene does not share estrogen's ability to reduce hot flashes.
Recent research findings about raloxifene include the following:
  • Postmenopausal women treated with raloxifene for 3 years showed about the same rate of overall mental decline as women treated with a placebo. However, the women on raloxifene had less decline in verbal memory and attention.
  • Raloxifene lowers homocysteine levels in postmenopausal women. High homocysteine levels increase the risk of coronary artery disease.
How does tamoxifen affect the body? Tamoxifen (i.e., Nolvadex) is a SERM that is used to treat breast cancer. It may be taken for about 5 years after a breast cancer diagnosis. This treatment helps prevent a recurrence of the cancer. It may also be used to prevent breast cancer in women who have many risk factors for breast cancer.
However, tamoxifen can increase the risk of endometrial or uterine cancer. Women who take tamoxifen should be monitored by their healthcare providers for signs of uterine cancer.
What are the side effects of SERMs? Following are current known side effects of raloxifene:
  • blood clots in the legs and, rarely, in the lungs
  • increased rate of hot flashes
  • leg cramps
Current known side effects of tamoxifen include the following:
  • blood clots in the legs and, rarely, in the lungs
  • hot flashes
  • rarely, uterine cancer
Who should NOT use SERMs?Raloxifene should not be used in women who are at increased risk of developing blood clots. This includes elderly women, bedridden women, and women with a history of blood clots.
In general, tamoxifen is not given to women at increased risk of developing blood clots. However, some women would benefit so much from tamoxifen that their healthcare providers may still recommend that they take the medication.

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