In the past, many women used menopausal hormone therapy (MHT) to relieve hot flashes and other symptoms of menopause. MHT is also known as postmenopausal hormone use and hormone replacement therapy.
Although MHT is approved for the short-term relief of menopausal symptoms, the U.S. Food and Drug Administration (FDA) recommends women use only the lowest dose that eases symptoms for the shortest time needed .
There are two main types of MHT used today:
Estrogen alone raises the risk of uterine cancer, so it's only used by women who no longer have a uterus (those who have had a hysterectomy).
Women who still have a uterus usually use estrogen plus progestin.
Estrogen plus progestin increases the risk of both developing and dying from breast cancer [19,179-183].
When women take these hormones, their risk of having an abnormal mammogram increases within the first year of use . And, their risk of breast cancer increases within the first 5 years of use [182-184].
The risk of breast cancer goes up slightly with each year a woman takes estrogen plus progestin . Small yearly increases in risk can add up over time.
Some large studies have found women who use estrogen plus progestin for 5 or more years (and are still taking it) about double their breast cancer risk [182-183].
When women stop taking MHT, the risk of breast cancer starts to decline.
After about 5-10 years, the risk returns to that of a woman who has never used MHT [19,181-182,184].
MHT may also have a negative impact on other aspects of women's health.
Results from the Women's Health Initiative, a large randomized clinical trial, showed that taking estrogen plus progestin for more than 5 years did more harm than good .
Although using estrogen plus progestin may lower the risk of endometrial cancer and hip (and other bone) fractures, these benefits were outweighed by increased risks of breast cancer and :
Study findings also show the use of estrogen plus progestin increases the risk of other conditions, such as cognitive decline (in women older than 65) and urinary incontinence (at least once a week) .
These findings are based on older forms of estrogen plus progestin MHT. Newer forms of estrogen plus progestin MHT are under study.
Figure 2.2 below shows the absolute risks and relative risks of some health conditions with the use of estrogen plus progestin compared to placebo.
Figure 2.2: Risks of select diseases with about 6 years of estrogen plus progestin (E+P) use versus placebo
Extra cases seen per 10,000 women who take E+P for a year:
Deep vein thrombosis
Fewer cases seen per 10,000 women who take E+P for a year:
Adapted from Women's Health Initiative findings .
Some studies have suggested estrogen alone increases the risk of breast cancer by about 30 percent [19,180,182-183].
However, the Women's Health Initiative showed a decreased risk of breast cancer with estrogen alone compared to placebo after an average of 7 years of use . In this study, most women began using estrogen many years after menopause, rather than at the time of menopause.
The results from two large cohort studies, where most hormone use started at menopause, raise the question of the safety of longer-term use of estrogen alone.
Researchers continue to follow the women in these studies to better understand how estrogen alone might affect breast cancer risk.
Some findings have suggested estrogen alone MHT may lower the risk of heart disease .
However, findings from the Women's Health Initiative showed the use of estrogen alone MHT for up to 7 years had almost no impact on risk .
Researchers continue to study this issue.
If you are considering taking MHT (estrogen plus progestin or estrogen alone), discuss the risks and benefits with your health care provider.
For short-term relief of menopausal symptoms, estrogen plus progestin is an approved MHT. However, the FDA recommends that it be used only at the lowest doses for the shortest time possible .
MHT is usually not given to breast cancer survivors because findings from large randomized controlled trials have shown it increases the risk of [189-190]:
Learn about other ways to treat menopausal symptoms.
For a summary of research studies on menopausal hormone therapy and breast cancer, visit the Breast Cancer Research Studies section.
Susan G. Komen’s breast self-awareness messages
1. Know your risk
2. Get screened
3. Know what is normal for you and see a health care provider if you notice any of these breast changes (see images):
4. Make healthy lifestyle choices
Facts for Life: How Hormones Affect Breast Cancer
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