The Who, What, Where, When and Sometimes, Why.

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. The FDA recommends women use the lowest dose of MHT that eases symptoms for the shortest time needed [268].

While there are different types of MHT that contain hormones (for example, vaginal suppositories and hormone patches), here we are talking about oral MHT (pills) and breast cancer risk.

The main types of MHT pills are:

  • Estrogen plus progestin
  • Estrogen alone

Estrogen alone is linked to an increased 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.

Learn about vaginal menopausal hormone therapy and hormone patches.

Estrogen plus progestin MHT

Risk of breast cancer

Women who use estrogen plus progestin MHT have an increased risk of breast cancer [20,269-273].

Within the first year of taking estrogen plus progestin MHT, women have an increased risk of having an abnormal mammogram [274]. Within the first 5 years of use, women have an increased risk of breast cancer increases [271-272,274].

Every year a woman takes estrogen plus progestin, her risk of breast cancer goes up slightly [273]. 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 [271-272].

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 [20,270-271,274].

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 women who took estrogen plus progestin for more than 5 years got more risks than benefits [275].

Although women who used estrogen plus progestin may have had a lower risk of colorectal cancer and hip (and other bone) fractures, those benefits were outweighed by increased risks of breast cancer and [275]:

  • Blood clots in the large veins (deep vein thrombosis)
  • Blood clots in the lungs (pulmonary embolism)
  • Stroke

Study findings also show the use of estrogen plus progestin is linked to an increased risk of other conditions, such as cognitive decline (in women older than 65), urinary incontinence and gallbladder disease [275,651].

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


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

12 extra


Cognitive decline*

23 extra


Pulmonary embolism

9 extra



9 extra



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


Colorectal cancer

6 fewer


Hip fracture

6 fewer


* In women 65 and older

Adapted from Women’s Health Initiative findings [275].


Estrogen alone MHT

Risk of breast cancer

Some studies have suggested women who use estrogen alone MHT have about a 30 percent increase in the risk of breast cancer [20,271-273].

However, the Women’s Health Initiative showed women who used estrogen alone had a decreased risk of breast cancer compared to women who received a placebo after an average of 7 years of use [276]. 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 [277]. However, there was an increased risk of breast cancer among these women after 20 years of use [277].
  • The NIH-AARP Diet and Health Study found women (especially those who were thin) who used estrogen alone for 10 or more years had an increased breast cancer risk [278].

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 is linked to a lower risk of heart disease is under study [275].

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 [268]. 

MHT after a breast cancer diagnosis

MHT is usually not given to women who have had breast cancer because findings from large randomized controlled trials have shown it’s linked to an increased risk of [279-280]:

  • 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):

  • 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 the 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

Download Komen’s Breast Self-Awareness Messages card for more information.

Updated 03/02/21