HRT pills carry increased risk of blood clots, research shows

BMJ research has found that HRT pills can increase the risk of blood clots – something that patches, gels and creams don’t do

A large-scale study by the BMJ has found that hormone replacement therapy (HRT) pills are associated with a higher risk of rare but serious blood clots (known as venous thromboembolism or VTE).

No increased risk was found for HRT skin patches, gels or creams – while this is comforting, the vast majority of women choosing HRT continue to be prescribed oral preparations.

HRT is used to relieve menopausal symptoms such as hot flushes and night sweats. Different treatments are available depending on the symptoms.

The researchers say these findings provide important information for women and their doctors to help them make the best treatment choices.

There is, alarmingly, is a lack of information on risks associated with different types of HRT.

As a result, Yana Vinogradova, a member of an epidemiological team at the University of Nottingham led by Julia Hippisley-Cox, set out to assess the association between VTE risk and all available types of HRT in the UK between 1998 and 2017.

Using two UK primary care databases (QResearch and CPRD), the two compared HRT prescription records of over 80,000 women aged 40-79 years who developed blood clots (cases) with those of over 390,000 women who did not (controls).

Other relevant factors such as lifestyle, family history of blood clots, and underlying conditions linked to blood clots were also taken into account.

Most HRT tablets were found to be associated with increased VTE risk (nine additional cases per 10,000 women per year) compared with no HRT.

Tablets containing equine oestrogen, including single and combined preparations, were consistently associated with higher risks than tablets containing synthetic oestrogen.

Higher doses of oestrogen were also associated with higher VTE risk. However, no increased VTE risk was found for skin patches, gels and creams.

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This is an observational study, and as such, can’t establish cause. Nevertheless, they say this study “has provided a more detailed picture of the VTE risks for different HRT preparations and can help clinicians and women make treatment choices.”

They suggest greater consideration should be given to transdermal HRT, particularly for women already at an increased VTE risk and in line with recent guidelines.

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