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Women's Health



This article is an update of current knowledge of risks and benefits of hormone replacement therapy


  • Hormone replacement therapy (HRT) replaces oestrogen which is reduced after  menopause
  • It effectively treats symptoms of menopause like hot flushes and night sweats
  • HRT is also used to treat osteoporosis and can reduce the rate of fractures
  • Recent research now shows that HRT is not beneficial in reducing heart and vascular disease and in fact slightly increases the risk.
  • Taking HRT for more than four years slightly increases the risk of breast cancer
  • The hormone progesterone should be used in combination with oestrogen for women with a uterus
  • The Women’s Health Initiative study in America (see links below) has provided good data and led to a change in thinking about many aspects of HRT

What is hormone replacement therapy?

Hormone replacement therapy or HRT replaces the declining oestrogen levels in the body after menopause. It is this declining level that results in the symptoms of menopause.

HRT normally contains artificial forms of the sex hormones oestrogen and progesterone that are only produced in small amounts after menopause. These hormones are the same ones found in the oral contraceptive pill. They are prescribed at lower concentrations in HRT.

HRT helps to reduce hot flushes, night sweats and vaginal dryness and can significantly slow the development of osteoporosis (thinning of the bones) with long-term use. It has also been found to reduce the incidence of colon cancer.

Is HRT for me?

The decision to start hormone replacement therapy (HRT) should not be taken lightly. Most women put a lot of thought into whether they need the treatment because it does come with associated risks which need to be weighed against the benefits.

HRT was once commonly thought to protect the heart from disease. It was thought to be beneficial even in menopausal women without symptoms. However, a large American study in 2002 called the Women’s Health Initiative (WHI) has changed the way we think about and use HRT.

The study was conducted in healthy woman with an average age of 63. It was the largest randomised study done with 16,608 participants. Half were randomised to receiving HRT and half to placebo treatment.

The study was stopped after 5.2 years because HRT was associated with increased rates of heart related diseases, stroke and breast cancer.

The study did not look at the risks and benefits of shorter-term HRT use for symptomatic relief, but rather looked at the risks associated with long term, continuous treatment in otherwise healthy, post-menopausal women. The results of the study (after 5.2 years) are summarised below.

The hormone replacement therapy given in the study was 0.625 mg of oestrogen and 2.5 mg of progestogen (the synthetic form of progesterone) compared with a placebo pill. The results showed that in patients randomly assigned to HRT:

·         Heart Attacks increased by 7 per 10,000 per year (from 30 in the placebo group to 37 taking HRT)

·         Strokes increased by 8 per 10,000 per year (from 21 in the placebo group to 29)

·         Breast Cancer increased by 8 per 10,000 per year (from 30 in the placebo group to 38)

·         Thromboembolic events (e.g blood clots) increased by 18 per 10,000 per year (from 16 events in the placebo group to 34)

·         Colorectal cancer decreased by 6 per 10,000 per year (from 16 in the placebo group to 10)

·         Hip Fractures decreased by 5 per 10,000 per year (from 15 in the placebo group to 10)

·         No difference in  endometrial cancer were found between the two groups

·         No difference in overall mortality was found between the two groups in the follow up period.

The increased risk of breast cancer was only observed after 4 years of treatment.

The risks associated with HRT increase as the duration of treatment increases and are reduced when treatment is stopped. The risk of heart attack and stroke decreases more substantially when treatment is stopped compared to the risk of breast cancer, which may remain elevated after treatment.

It is important to recognise that the results from the WHI are not directly applicable to short-term use of HRT.

Since the publication of the WHI, reviews have been conducted which combine data from multiple studies and these show similar results.

This is compelling evidence that long-term, continuous use of HRT does come with risks.

New guidelines published in 2013 suggest that it is the timing of HRT that is important in determining its associated risk. The guidelines suggest that the benefits of HRT outweigh the risks in symptomatic women under 60, within 10 years of menopause. The symptoms of menopause may however come back when treatment is stopped.

One recent study presented in May 2015 suggests that HRT may increase the risk of bleeding from the lower gut by up to 50%. This risk is increased as the length of time on HRT increases.    

Another study has shown that HRT is associated with an increased risk of ovarian cancer. The study suggests that 1 additional ovarian cancer will occur for every 1000 women treated with HRT for 5 years.

A number of studies have shown that HRT increases the risk of gallbladder inflammation even with short-term use. Other studies suggest that this isn’t the case and this outcome has not been reported by the WHI.

The decision to start HRT treatment is clearly an intricate issue and should be made on a case-by-case basis in collaboration with a trusted doctor. Each individual’s personal level of risk should be factored into the decision-making as well as the potential benefits gained from HRT.


Women who decide against HRT may find alternative treatments beneficial. These include supplements such as black cohosh, evening primrose oil, acupuncture, and homeopathic remedies. Some believe phytoestrogens found in some foods (soy milk and tofu) are helpful. However there isn’t a strong evidence base for these treatments.

If HRT is used there are ways to reduce any additional risk of heart disease, including not smoking, being a healthy weight and controlling high blood pressure and cholesterol levels.

HRT should not be taken by women with a history of breast cancer, blood clots, pulmonary embolus or unexplained vaginal bleeding. Caution may be needed with liver and gallbladder disease.

Those at high risk of osteoporosis could consider taking HRT to help prevent fractures. These include women with low body weight, a past history of smoking, premature menopause and a family history of the condition. There are other effective treatments for low bone density.

Which product to choose?

The lowest dose of oestrogen that can control the symptoms of menopause is normally prescribed. Progesterone is included at the end of the monthly cycle in an effort to mimic the body's natural cycle and to reduce the risk of endometrial cancer in women with a uterus.

Women who have had a hysterectomy (uterus removal) do not need treatment with progesterone.

A continuous combination of oestrogen and progesterone may suit many women as this treatment does not result in any regular bleeding (apart from in the first few months). It is usually not recommended until 2 years after the end of periods. It is possible that there will be some bleeding (similar to periods) while on HRT (particularly when starting it). You may want to speak to your doctor about this.

In the WHI, there was a branch of the study that looked at whether oestrogen-only treatment of post-menopausal symptoms came with a lower risk than use of both oestrogen and progesterone. This part of the study was stopped after 7 years as it showed that oestrogen did increase the risk of strokes compared to the placebo group.

HRT can be taken in tablet form, with skin patches that slowly release hormones into your body, and by using implants under the skin. It is believed that oestrogen patches have fewer side effects and cause less deep vein thrombosis than the tablets.

Oestrogen creams applied to the vagina and pessaries can help relieve problems with vaginal dryness and reduce the risk of urinary tract infections. They come with a much lower risk as they act locally and help rebuild the vaginal wall. However, they are not as effective as hormone tablets.

Women should have a breast examination and a breast screening mammogram when they start HRT and continue regular self-examination and regular breast examinations and mammograms (1 to 2 yearly depending on the circumstances).



  • HRT can effectively relieve hot flushes and vaginal dryness
  • Bone loss from osteoporosis is reduced  
  • It can help ease mood swings and improve sleeping patterns
  • It may reduce facial hair
  • It may reduce the risk of colon cancer
  • It may reduce the risk of Alzheimer's disease (research not complete)


  • Some types of HRT may bring back vaginal bleeding ("periods")
  • Side effects include breast tenderness, headaches, bloating and nausea
  • There is an increased risk of breast cancer but no known increased risk of death from breast cancer.
  • There is a slightly increased risk of endometrial cancer unless taken with progesterone
  • The risk of deep vein thrombosis and thromboembolism (blood clots) is increased
  • The risk of heart attack and stroke is increased in the long term
  • The risk of ovarian cancer is increased in the long term
  • Risk of lower gut bleeding may be increased in the long term
  • May increase the risk of gallbladder inflammation (cholecystitis)

See also:

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