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Home > Understanding Breast Cancer > Risk Factors and Prevention > Reproductive Risks > Menopausal Hormone Therapy (Postmenopausal Hormone Use)


Menopausal Hormone Therapy (Postmenopausal Hormone Use)


How Hormones Affect Breast Cancer
Fact Sheet

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 [153].  

There are two main types of MHT used today:

  • Estrogen plus progestin
  • Estrogen alone

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

Risk of breast cancer

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 [155]. 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 [157].  

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].  

Other health risks

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 [160]. 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 [160]:

  • Deep vein thrombosis (blood clots in the large veins)
  • Pulmonary embolism (blood clots in the lungs)
  • Stroke

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) [160].  

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 


Absolute risk 

Relative risk 


Extra cases seen per 10,000 women who take E+P for a year: 


Breast cancer

9 extra


Deep vein thrombosis

4 extra


Pulmonary embolism

4 extra



5 extra



Fewer cases seen per 10,000 women who take E+P for a year: 


Endometrial cancer

3 fewer


Hip fracture

5 fewer


Adapted from findings from the Women's Health Initiative [160].


Estrogen alone

Risk of breast cancer

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 [160].

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 [161]. 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 [162]. Researchers continue to follow the women in these studies to better understand how estrogen alone might affect breast cancer risk.

Other health risks

Findings from early cohort studies and a 2012 randomized clinical trial suggested estrogen alone MHT lowered the risk of heart disease [163]. 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 [160]. Researchers continue to study this issue.

Recommendations for menopausal hormone therapy

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 [153].

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

  • Talk to both sides of your family to learn about your family health history  
  • Talk to your health care provider about your personal risk of breast cancer

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):

  • Lump, hard knot or thickening inside the breast or underarm area
  • Swelling, warmth, redness or darkening of the breast
  • Change in the size or shape of the breast
  • Dimpling or puckering of the skin
  • Itchy, scaly sore or rash on the nipple
  • Pulling in of your nipple or other parts of the breast
  • Nipple discharge that starts suddenly
  • New pain in one spot that doesn't go away

4. Make healthy lifestyle choices


Updated 11/12/13 

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