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HRT Risks

Recent research about the safety and benefits of HRT has changed medical advice about what HRT can be used for. HRT was recommended for the relief of menopausal symptoms, but it was also sometimes recommended to healthy women (without menopausal symptoms) as a long-term treatment to help prevent osteoporosis and offer protection against heart disease and other problems of ageing, such as Alzheimer’s disease.

The Committee on Safety of Medicines no longer recommends HRT is as safe to use for a long-term treatment because of safety concerns (detailed below). The concerns have been raised by recent studies including the Million Women Study (2003, UK trial) and the Women’s Health Initiative (2002, US trial).

Summary of risks from the Medicines and Healthcare Products Regulatory Agency and the Committee on Safety of Medicines
The increased risks of taking HRT are small. Women who do not take HRT can also develop these conditions. Any risk assessment needs to take into account a range of factors including life-style and family history.

Breast Cancer

• Women who do not take HRT: About 32 in every 1000 women aged 50 (who do not take HRT) will get breast cancer by the time they reach 65.
• Oestrogen only HRT: In women aged 50 who take oestrogen only HRT for five years, about 33.5 in every 1000 will get breast cancer. That is only an extra 1-2 cases. If they take it for ten years this could rise to 37 cases in a 1000. Results from the oestrogen only study form the Women’s Health Initiative released in early 2004 found that women who took oestrogen only HRT had no increased risk of breast cancer.
• Combined HRT started at age 50: The number of cases that would be diagnosed by 65 would be 38 cases in a 1000 after 5 years i.e. an extra 6 cases, and 51 in a 1000 after 10 years i.e. an extra 19 cases. Results from a recent Swedish study found that continuous combined ‘bleed-free’ products carried the highest risk.
• Tibolone: The risks of breast cancer have not been studied for this product but are thought to be between those for oestrogen only and combined HRT.

Cancer of the Womb Lining

Taking oestrogen only HRT makes the womb lining thicken, and this increases the risk of cancer developing. This risk is reduced (but not totally eliminated) by taking progesterone which gets rid of any excess womb lining in the form of a withdrawal bleed. Any abnormal bleeding which begins after starting HRT needs to be investigated.

Ovarian Cancer

Using oestrogen only HRT for more than 5 years may slightly increase the risk of getting this rare but serious cancer. It is not yet known what effect combined HRT has on ovarian cancer.

Heart disease

The latest advice is that HRT does not protect against heart disease as was previously thought. Also products which contain conjugated oestrogen (oestrogen from the urine of pregnant mares) and a type of progestogen called medroxyprogesterone may increase the risk of heart disease in the first year of use.

Stroke

HRT slightly increases the risk of having a stroke. For women in their 50s who do not take HRT about 3 in every 1000 will have a stroke in any 5 year period compared to about 4 in a 1000 women of the same age who take HRT for five years.

Stroke risk goes up with age. For women in their sixties who do not take HRT, about 11 in a 1000 will have a stroke over a 5 year period compared to about 15 in a thousand women who use HRT for five years.

Venous thromboembolism

Harmful clots can develop in the veins. If a clot develops in the deep veins of the legs it is called a Deep Vein Thrombosis (DVT). If a part of the clot breaks off and moves into the lungs it can cause a potential life threatening obstruction called a pulmonary embolism. The term venous thromboembolism (VTE) covers both deep vein thrombosis and pulmonary embolism.

Research shows that women who take HRT are more likely to develop a VTE than those who don’t, especially in the first year of using HRT: for women in their fifties who do not use HRT, about 3 in a 1000 will have a VTE over 5 years compared to 7 in a 1000 women of the same age who use HRT for 5 years.

Dementia

Contrary to what was previously thought, research currently shows that HRT has no beneficial effect on mental functioning and may increase the risk of dementia later in life.

Weighing up the risks

Despite the current safety recommendations, it is important to emphasise that the increase in risks identified by these studies is small (in a study done by the Imperial Cancer Research Fund, reported in the late 1990s, the risks linked to HRT rapidly reduced after stopping HRT and disappeared after five years). Each woman needs to discuss the pros and cons of HRT with their doctor to see if it is suitable for them. Some doctors may agree to prescribe HRT for longer for those women who feel that the benefits of HRT outweigh its risks.

Reducing HRT risk

At the moment some research suggests that oestrogen only products may have a lower breast cancer risk than combination products but this needs to be confirmed by further research. Many women need to take progestogen because they still have a womb. It may be safe to deliver progestogen with the Mirena device, although more research is needed to confirm this. Some doctors believe this might be a better option as the progestogen just acts in the womb rather than affecting the whole body.

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Written by Judy Fairlie and updated by Mary-Claire Mason for Women’s Health
and published in printed format by Women's Health

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