Menopausal Hormone Therapy
Menopausal hormone therapy (MHT) is approved by the U.S. Food and Drug Administration (FDA) for the short-term relief of hot flashes and other symptoms of menopause. However, the FDA recommends women use the lowest dose of MHT that eases symptoms for the shortest time needed .
There are 2 main types of MHT:
- Estrogen plus progestin
- Estrogen alone
Estrogen alone raises the risk of uterine cancer. So, it’s only used by women who no longer have a uterus (those who’ve had a hysterectomy).
Women who still have a uterus usually use estrogen plus progestin.
Estrogen plus progestin
Risk of breast cancer
Estrogen plus progestin MHT increases the risk of [20,255-259]:
- Breast cancer
- Breast cancer death
When women take estrogen plus progestin, 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 [257-258,260].
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 [257-258].
When women stop taking estrogen plus progestin, their 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 [20,256-257,260].
Other health effects
Estrogen plus progestin MHT may have other health risks. Results from the Women’s Health Initiative, a large randomized clinical trial, showed 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 :
- Blood clots in the large veins (deep vein thrombosis)
- Blood clots in the lungs (pulmonary embolism)
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 .
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: Risks of select diseases with about 6 years of
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 .
Risk of breast cancer
Some studies have suggested estrogen alone increases the risk of breast cancer by about 30 percent [20,257-259].
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. So, the effect on breast cancer risk may vary by when it’s first used.
The results from 2 large cohort studies, where most hormone use started at menopause, 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 . However, there was an increased risk of breast cancer after 20 years of use .
- The NIH-AARP Diet and Health Study found the 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.
Heart disease benefit – under study
Whether estrogen alone MHT may lower the risk of heart disease is under study [261,264].
Recommendations for MHT
If you are considering 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 it be used only at the lowest dose for the shortest time possible .
MHT after a breast cancer diagnosis
- Local breast cancer recurrence
- Metastasis (distant recurrence)
- Cancer in the opposite breast
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.
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
Download Komen’s Breast Self-Awareness Messages card for more information.