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 is only used by women who no longer have a uterus (those who have had a hysterectomy). Women who still have a uterus most often use estrogen plus progestin.
Estrogen plus progestin increases the risk of both developing and dying from breast cancer [19, 154-158]. When women take these hormones, their risk of having an abnormal mammogram increases within the first year of use [157,159]. And, their risk of breast cancer increases within the first five years of use [157-159].
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. One large study found women who use estrogen plus progestin for five or more years (and are still taking it) more than double their breast cancer risk .
When women stop taking MHT, the risk of breast cancer starts to decline. After about five to 10 years, the risk returns to that of a woman who has never used MHT [19,156-157,159].
MHT also has 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 five years does more harm than good . Although using estrogen plus progestin may lower the risk of endometrial cancer and hip (and other bone) fractures, these benefits are outweighed by increased risks of breast cancer and :
Study findings also show that the use of estrogen plus progestin also increases the risk of other conditions, such as cognitive decline (in women older than 65) and urinary incontinence (at least once a week) .
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 selected diseases with at least five years of estrogen plus progestin (E+P) use versus placebo after eight years of follow-up
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:
Some studies have suggested estrogen alone increases the risk of breast cancer by about 30 percent [19,155,157-158]. However, the Women's Health Initiative trial showed a decreased risk of breast cancer with estrogen alone compared to placebo after an average of seven years of use .
The results from two large cohort studies raise the question of the safety of longer-term use of estrogen alone. As in the Women's Health Initiative, the Nurses’ Health Study found no increased risk of breast cancer among women who used estrogen alone for less than 10 years. But, there was an increase in risk of breast cancer after 20 years of use . The NIH-AARP Diet and Health Study found use of estrogen alone for 10 or more years increased breast cancer risk, especially in women who were thin . Researchers continue to follow the women in these studies to better understand how estrogen alone might affect breast cancer risk.
Findings from early cohort studies and a 2012 randomized clinical trial suggested estrogen alone MHT lowered the risk of heart disease . However, findings from the Women's Health Initiative showed use of estrogen alone MHT for up to seven 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, but the FDA recommends that it be used only at the lowest doses for the shortest time possible .
Learn about alternatives to menopausal hormone therapy for the relief of menopausal symptoms.
For a summary of research studies on menopausal hormone therapy and breast cancer, visit the Breast Cancer Research 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 your 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
Discover the different ways you can help