Hormone replacement therapy

Menopause is the transition from a woman’s childbearing years to her non-childbearing years. This change in hormone levels may cause:

  • hot flashes
  • sleep disturbances
  • mood swings

These symptoms typically continue for several years until menstrual periods stop completely. This often happens in the early 50s but can vary a lot. Women with cancer may enter menopause early as a side effect of chemotherapy or other treatments.

The decision on whether to undergo hormone replacement therapy (HRT) during menopause is personal and should be made in consultation with your doctor. Concerns about cancer, heart disease and stroke should be discussed when considering the risks and benefits of HRT.

Our recommendation

The Canadian Cancer Society recommends that women avoid taking HRT for any reason other than to relieve severe menopausal symptoms that have not responded to other treatment.

If you are thinking about taking HRT, your decision should be made with your doctor based on the risks and benefits associated with taking it. These include:

  • how severe your menopausal symptoms are
  • your individual and family history of heart disease, breast and ovarian cancer, osteoporosis and dementia
  • how long you will be taking HRT

If you and your doctor decide that taking HRT is right for you, the lowest effective dose should be used for the shortest period of time possible to control the menopausal symptoms for which it was started in the first place.

Uses of HRT

During menopause there are changes in a woman’s natural hormones. These changes can cause symptoms such as hot flashes, sleep disturbances and mood swings. Some women take hormone replacement therapy (HRT) to relieve these symptoms.

HRT can be taken as estrogen only or as a combination of estrogen plus progestin (combined HRT). Taking estrogen alone can cause cancer in the lining of the uterus, so women who have had their uterus removed surgically (hysterectomy) may take estrogen alone as they no longer have this cancer risk. Combined HRT is more commonly used by women with an intact uterus.

Combined HRT may help relieve menopausal symptoms, protect against osteoporosis (thinning of the bones) and reduce risk of colon cancer, but research also shows that long-term use of combined HRT (for 5 or more years) also increases the risk of breast cancer, ovarian cancer, heart disease, stroke and pulmonary embolism (blood clots in the lung). The research suggests that the risks of long-term combined HRT use outweigh the benefits for most women.

HRT and cancer

There is convincing evidence that using HRT raises a woman’s risk of cancer. There are other health concerns as well.

Breast cancer
According to the International Agency for Research on Cancer, combined HRT for menopause is a known cause of breast cancer, mainly in women who recently used or are still using the therapy.

In 2002, a large clinical trial in the United States called the Women’s Health Initiative (WHI), which involved 16,600 women aged 50-79, reported a 25% increase in breast cancer risk among women who took combined HRT compared to those who took a placebo. This meant roughly 8 extra cases of breast cancer occurred for every 10,000 women taking combined HRT. Women on combined HRT were also more likely than those taking the placebo to have breast cancer found at a more advanced stage and to die from breast cancer. They were also more likely to have abnormal mammograms.

A number of follow-up studies from the WHI have since been published. The follow-up studies, along with other international research on combined HRT, have provided a better picture of the benefits and risks offered by combined HRT use in menopause. The risk of breast cancer is greatest when combined HRT is used:
  • for 5 years or more (the risk increases the longer a woman uses HRT)
  • by older postmenopausal women, especially those over the age of 60
  • by women who start taking HRT closer to menopause
  • by slim women
  • by women with dense breasts
The WHI also included a clinical trial comparing the use of estrogen-only HRT to a placebo. Over 10,000 postmenopausal women who no longer had a uterus took part. Women who took estrogen and had no family history of breast cancer and no history of benign (non-cancerous) breast disease had a slightly lower risk of breast cancer compared to women who took the placebo.

Ovarian cancer
Overall, studies suggest that both combined and estrogen-only HRT increase a woman’s risk of ovarian cancer but that the risk is low. Research done by the Collaborative Group on Epidemiological Studies of Ovarian Cancer showed that women who took HRT have a higher risk of ovarian cancer. How recently they used HRT was the most important factor in that risk. Women currently using HRT had the greatest increased risk compared to women who used it in the past. The risk went down over time once a woman stopped taking HRT. The Collaborative Group study also showed that the risk increases with the length of time a woman has used HRT.

Colorectal cancer
The research is mixed on the effect of combined HRT on colorectal cancer. Some studies suggest a decreased risk (a protective effect) among users of combined HRT, while others do not. The WHI study found no effect of estrogen-only therapy on colorectal cancer, but some studies suggest a decreased risk (a protective effect) of colorectal cancer in women taking estrogen-only therapy.

Other health concerns
According to the WHI, regular use of combined HRT appears to increase the risk of heart disease, stroke and pulmonary embolism (blood clots in the lungs). Women taking combined HRT were more likely to require endometrial biopsies and need follow-up testing for vaginal bleeding. Using combined HRT regularly seemed to decrease the risk of hip fractures.

The WHI found that women taking estrogen-only HRT had an increased risk of stroke and venous thrombosis (a blood clot in a vein), but they had a decreased risk for bone fractures.

Suggested links on HRT and cancer risk

Reports on the health benefits and risks of HRT
International Agency for Research on Cancer
Monograph 91 on Combined Estrogen-Progestogen Menopausal Therapy

Health Canada
Benefits and Risks of Hormone Replacement Therapy
The Safe Use of Natural Health Products During Menopause

Research on cancer risk of HRT
The Lancet
Menopausal hormone use and ovarian cancer risk: individual participant meta-analysis of 52 epidemiological studies (February 2015)

Journal of the American Medical Association
Hormone Therapy and Ovarian Cancer (July 2009)
Effects on Breast Cancer and Mammograms (June, 2003)
Risks and Benefits of Estrogen Plus Progestin in Healthy Postmenopausal Women (July, 2002)

New England Journal of Medicine
Breast Cancer after Use of Estrogen plus Progestin in Postmenopausal Women (February 2009)

American Journal of Epidemiology
Estrogen plus progestin therapy and breast cancer in recently postmenopausal women (March, 2008)

Alternatives to HRT

Women who decide not to take hormone replacement therapy (HRT) and who experience many menopausal symptoms often seek relief in other ways. Not all of the alternatives to HRT have been scientifically proven, but many women do find them helpful.

What you can do to help sleep troubles

  • Exercise. Being active relieves stress and improves overall well-being which may help you to sleep better.
  • Try relaxation techniques (deep breathing, massage or yoga). These may help reduce your stress levels.
  • Sip a chamomile tea or tea containing valerian at bedtime. Avoid caffeine and alcohol as they can make menopausal symptoms worse.

What you can do to control hot flashes

  • Get as much exercise as you can.
  • Choose light clothing and wear it in layers that can be removed.

What you can do to relieve vaginal dryness

  • Use a water-soluble lubricant or moisturizer available at your pharmacy.
  • Ask your doctor about a vitamin E vaginal suppository or cream to help relieve symptoms.

Not all the above alternatives to HRT have been tested to evaluate side effects. Hormone replacement therapy may still be useful to ease the symptoms of menopause for short-term use over several months – when the alternatives to HRT do not work and the symptoms are severe.

Always check with your doctor before making a decision about hormone replacement therapy, taking any herbal products or making any lifestyle changes.