Menopause

5.4. Risks of hormone therapy

Assessing the risks of HT is not simple. This is because there are so many variations on the market, used in different combinations and forms. The longterm use of two particular forms of oestrogen-based therapy is the best studied. One includes so-called conjugated oestrogen (0.625 mg daily) and the other combines the same dose of oestrogen with the progesterone called medroxyprogesterone (2.5 mg daily). These treatments were tested in the USA in around 27,000 for six years. Both of these treatments are commonly prescribed in other countries, including Germany.

Because there have not been direct comparisons between all the different forms of HT, it is not clear whether the harms that happened in this big trial are the same or worse for other forms of HT. So experts have different opinions, in the absence of a clear answer. Internationally, drug regulatory authorities have decided that women would be more protected if it was assumed that all hormone treatments have the same risk of causing harm [36],[47]. One thing is clear though: the potential harms of combined HT are different to those of taking oestrogen alone.

Heart attack and stroke

Many people used to think that HT could protect women from heart attacks. But this hope has faced a strong setback in recent years [35],[44],[48]. There is no known impact on heart attacks for women without a uterus who take oestrogen alone [35]. But women who are taking combined oestrogen therapy have a slightly increased risk of having a heart attack, particularly in the first year they are taking the drugs [35].

If a women has already been taking HT for years without having a heart attack, then her risk is no longer any higher than that of women who did not take HT. The question of whether or not HT might be able to reduce the risk of heart attack in younger women - those around 50 - is still unanswered. However this would not be likely to be a big difference, because heart attacks in healthy women around 50 are uncommon.

The risk of stroke also increases for women who take hormones for the menopause. That is true for both oestrogen alone and combined oestrogen therapy [35].

The numbers of women who have these adverse effects is shown in the table at the end of this article.

Thromboembolism

A serious illness that needs to be taken into account with HT is thromboembolism. This happens when a blood clot gets stuck in a blood vessel, for example in the leg or in the lungs [35]. Here again there are differences between oestrogen alone and combined therapy: women taking oestrogen alone do not have a higher risk of thromboembolism [35]. But for women taking combination HT, the risk starts to increase from the start of treatment and keeps increasing. You can see more in the table on adverse effects at the end of this article.

Breast cancer

Breast cancer is the potential complication from HT that has received the most attention. And again, there are differences depending on whether the treatment is monotherapy or combined oestrogen therapy. For women who take combined therapy for longer than five years, the risk of breast cancer noticeably rises [35]. But for women who are only taking oestrogen because they do not need progesterone to protect their uterus, the picture is not so clear. According to the results of the major trial, there was no increased risk of breast cancer [35]. But international drug regulatory agencies have nevertheless considered that longterm treatment with oestrogen alone might also increase the risk of breast cancer. [36], [37],[38],[39],[40].

Some analysis has suggested that the risk of breast cancer from HT might be higher for European women than it was for the American women in the major trial [49]. One of the reasons for this might be because European doctors prescribe different hormones than their colleagues from the USA, at least in part.

You can read more about the risks of breast cancer in the table at the end of this article.

Other adverse effects

Both forms of oestrogen-based therapy taken for five to seven years increase the risk of gallbladder disease serious enough to need an operation [35]. You can see how often this happens in the table at the end of this article.

The trial also had disappointing results about dementia: HT did not protect women against cognitive impairment or dementia. In fact, if anything, HT might be more likely to have a negative impact on cognitive ability in women older than 65 [35].

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