Menopause hormone therapy (MHT), also referred to as hormone replacement therapy (HRT), is a commonly prescribed treatment offered to women to relieve menopausal symptoms, such as hot flushes, night sweats and mood swings. These symptoms can be debilitating, not only for the woman herself but they can also impact others around her, in work and at home. Despite this, many women have concerns about the potential risks associated with MHT.

This article was included in issue 98 (Autumn 2023) of The Menopause Exchange newsletter.

MHT may be prescribed in a sequential regime, oestrogen daily with progestogen taken for two out of every four weeks to mimic the menstrual cycle, or in a combined regime, where oestrogen and progestogens are taken every day. In this article, we discuss some of the potential risks of MHT, including cancer, stroke, blood clots and cardiovascular disease, and analyse increased risk between women who take MHT and those who don’t.

Understanding the risks

Cancer
One of the main concerns surrounding MHT is its association with cancer. The one that most women tend to worry about is breast cancer. Studies have shown that there may be a small increase in the risk of breast cancer for women using MHT when using combined oestrogen and progestogen therapy. The oestrogen in most prescribed MHT is oestradiol. This is the most potent of the oestrogens made by the ovaries. There are many different types of progestogens, and most are synthetic. It’s the type of progestogen within the MHT that is associated with the small, but real increased risk of breast cancer.

According to data published by NICE guidelines and the British Menopause Society, there will be an extra two cases of breast cancer per 1000 women per year. This risk is considerably less than drinking two or more units of alcohol per day. In women without a uterus, there’s no need to take progestogens, so the risk is even smaller, and studies have shown that there’s no risk with oestrogen taken transdermally (through the skin, e.g. patches, the spray or gels). Studies have also shown that in women who develop breast cancer while on MHT, their chances of survival are higher than if they’re not on MHT.

The risk of endometrial cancer (cancer of the lining of the uterus/womb) is slightly increased with sequential formulations. However, when MHT is taken continuously (oestrogen and progestogen daily), it actively protects the endometrium. Women with a high body mass index (BMI) of over 30 should discuss the dose of progestogen they’re taking with their healthcare professional, as obesity is associated with an increased risk of endometrial cancer whether or not they take MHT.

Stroke and blood clots
Another risk associated with MHT is an increased chance of stroke and blood clots. The risk appears to be slightly higher in women using MHT, particularly in the over-60s. Despite this, the overall risk remains low. However, this risk is only seen in women taking oral MHT (tablets or capsules) with no increased risk with transdermal oestrogen. Progestogens should be prescribed for women with a uterus. In fact, transdermal MHT can be prescribed safely, even if there’s a personal history of clots or strokes.

Cardiovascular disease
Cardiovascular disease, which includes heart attacks and other heart-related conditions such as angina, is a concern for women on MHT. Studies have shown conflicting results regarding the risk of cardiovascular disease associated with MHT. Some research suggests a slightly increased risk, while others indicate no significant difference between MHT users and non-users.

However, we still need to look at the studies more closely and at the timing of starting MHT. Starting HRT within 10 years of a woman’s last menstrual period has been shown to be actively protective.

Overall, the risk of cardiovascular disease is low for women using MHT. But it’s essential that women who have existing cardiovascular risk factors discuss their individual situation with their healthcare professional before starting MHT.

Transdermal or oral MHT risks
Transdermal MHT carries no risk of adverse effects when compared to oral MHT. When MHT is taken orally, it gets broken down in the liver, which can lead to an increased risk of blood clots. In contrast, transdermal MHT bypasses the liver, removing this risk. Additionally, transdermal MHT may be a suitable option for women who can’t, or prefer not to, take hormone therapy orally.

So, does MHT have lots of risks?
MHT is a beneficial treatment for managing menopause symptoms, providing relief and improving quality of life for many women. While there are some risks, these are minimal, and the overall increase in risk for conditions such as cancer, stroke, blood clots and cardiovascular disease is very small. MHT will actively protect women from common diseases associated with aging and poor lifestyle. These include osteoporosis and diabetes, as well as those mentioned above. Exciting studies suggest there’s a possible protective effect from dementia if MHT is started within five years of a woman’s last menstrual period, but we await further definitive research.

It’s crucial that women are given the RIGHT information at the RIGHT time for the RIGHT reasons by healthcare professionals, so they’re able to make an informed choice about their health. MHT isn’t suitable for everyone, and other treatments or lifestyle changes may be recommended for some people. It’s crucial to stay informed and have open discussions with your healthcare professional.

About the author
Dr Joanne Hobson is clinical lead director of The Menopause Consortium, a British Menopause Society menopause specialist, and a member of the Institute of Psychosexual Health.

Created Autumn 2023
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