Hormone replacement therapy can be a godsend for women suffering debilitating menopause symptoms. But what about potential side effects? Lisa Salmon reports

HORMONE replacement therapy (HRT) can have a hugely beneficial effect on unpleasant menopause symptoms, reducing hot flushes, night sweats and mood swings, and improving quality of life for many of the one million UK women who take it.

But there are fears about the therapy's side effects, with the latest research suggesting HRT - which usually involves the replacement of oestrogen and sometimes progesterone - could be associated with an increased risk of hearing loss in postmenopausal women.

Past studies have claimed HRT increases the risk of breast cancer, although more recent reviews have shown the association was exaggerated. Then there's cardiovascular disease; some studies say HRT is protective, others say it increases the risks.

Confused? Here's an outline of the current thinking on some of the benefits and risks of HRT...

Does HRT increase the risk of breast cancer?

There was a sharp decline in the number of menopausal women taking HRT following a 2002 study by the US Women's Health Initiative (WHI) that claimed there was an increased risk of breast cancer with the use of oestrogen plus progesterone HRT.

However, a recent review of the evidence has highlighted serious errors in the WHI report, and Dr Heather Currie, chair of the British Menopause Society (BMS), stresses that the study didn't show any statistically significant increased risk.

She explains it was designed to test the effects of HRT on older women, yet the conclusions applied exaggerated risks to all women. "Clinicians have been struggling for nearly 15 years to disprove some of the information in the report, which was incorrectly deemed as factual," she says.

Current evidence shows the risks are small and, for most women, outweighed by benefits, including symptom control and improved urogenital, bone and cardiovascular health.

Does HRT increase the risk of heart disease?

Despite numerous studies, the effect of HRT on heart disease is unclear. The WHI study found HRT increased the risk of heart disease in healthy postmenopausal women, yet 2012 Danish research found women receiving HRT soon after menopause had a significantly reduced risk of mortality, heart failure, or heart attack.

The National Institute for Health and Care Excellence (NICE) says HRT doesn't increase cardiovascular risk when started in women aged under 60, and it doesn't affect the risk of dying from cardiovascular disease. Yet the British Menopause Society says the ELITE trial, which looked at the effect of starting HRT within six years of the menopause or after 10 years, has shown starting HRT early is beneficial.

So the theory is there's a window of opportunity when early use of oestrogen after menopause may protect against heart disease.

Does HRT cause hearing loss?

Studies have found that while menopause may increase the risk of hearing loss, possibly because of reduced oestrogen levels, postmenopausal HRT might slow hearing decline by replacing oestrogen. Yet this month, new US research has suggested postmenopausal HRT may be associated with a higher risk of hearing loss.

But Dr Currie warns that the research relied on women's self-reported hearing loss and doesn't prove HRT causes it, just that there may be an association. "This should not terrify women and, as we have always said, the decision about HRT should be an individual choice based on the balance of benefits and risks."

Does HRT increase the risk of ovarian cancer?

A 2015 Oxford University analysis of 52 studies found HRT causes a small increase in the risk of ovarian cancer, with one extra case for every 1,000 women taking HRT for five years from the age of 50. Conversely, another 2015 study, from The Institute of Cancer Research, found women with the most common type of ovarian cancer can safely take HRT, and it could even improve their survival chances.

Does HRT prevent osteoporosis?

The major underlying cause of postmenopausal osteoporosis is the loss of bone resulting from oestrogen deficiency. Oestrogen helps increase bone mineral density and can also help prevent osteoporotic fractures in women. Several international medical organisations have stated HRT is effective for preventing osteoporosis-related fractures in at-risk women before the age of 60, or within 10 years after menopause.

Does HRT increase the risk of blood clots and strokes?

A 2015 Cochrane review of existing research confirmed HRT increases the risk of strokes and blood clots, such as deep vein thrombosis. Researchers estimated that for every 1,000 women taking HRT, an extra six would have a stroke and an extra eight experience a blood clot. But Dr Currie points out that the risks are affected by the route of HRT used, with transdermal oestrogen (by patch or gel) showing no increased risk of blood clot, compared with women not taking HRT.


Dr Currie points out that not every menopausal woman wants HRT, and some can't have it because of personal or family medical history (such as breast cancer).

"Many studies have been published over the past 15 years that have highlighted the potential risks of HRT," she says. "As a result, some women and doctors have been reluctant to use it, and women who needed HRT, but avoided it have suffered unnecessarily."

She says recent reanalysis of the data and consideration of further research has led to a better understanding of the risks. "Evidence shows the risks are small and, for most women, outweighed by the benefits if treatment is started before 60, or within 10 years of the menopause."

Dr Currie says the decision to use HRT (or not) should be made by women who've been given clear, evidence-based information by a healthcare professional, including information about complementary therapies, lifestyle and dietary changes.

HRT dosage and duration should be individualised, with an annual evaluation of the pros and cons, she says.

"It's important women find out what treatment options work for them, as the risks and benefits are different for each woman, depending on her medical history, family history, and symptoms."