1.Breast cancer– current research shows that HRT taken for 5 years or less has very little to no increased risk of breast cancer depending on the type of HRT used.
Oestrogen alone and combined HRT using oestrogen and micronized progesterone has no increased risk (oestrogen alone has actually been shown to reduce risk).
Combined HRT with a progestogen has a very small increased risk over 5 years.
After 5 years the risk of all combined HRT confers a slightly increased risk of breast cancer which reduces on stopping the HRT.
2.Blood clots– tablet form of HRT has been shown to cause a small increased risk of blood clots. This has to be taken into context with other risk factors for blood clots such as smoking and BMI and the pros and cons carefully discussed and in some circumstances a transdermal preparation may be suggested instead.
Some women may have a strong family history of blood clots or may be known to have a medical condition that increases the risk of blood clots in which case transdermal oestrogen would be strongly recommended.
There is good evidence that transdermal oestrogen does not increase clot risk.
Some progestogens are higher risk for blood clots than others and this may also need to be taken into consideration when prescribing HRT.
3.Ovarian cancer- we do not have good studies looking into the risk of ovarian cancer with HRT but one study showed a very small increased risk of 1 in 2,500. Other studies have not shown a significantly increased risk.
4.Heart disease- the relationship between HRT and heart disease has been one of controversy over the years. Current thinking is that there is a ‘window of opportunity’ where HRT is beneficial for the heart (within 10 years of the menopause or < age 60) and after this the effect is likely to be neutral on the heart rather than harmful. However in women who have unstable cardiovascular disease HRT is contraindicated until the heart disease is considered ‘stable’ and even then may require discussion with a heart specialist if restarting HRT is desirable.
5.Endometrial cancer- giving oestrogen alone to a woman with a uterus incurs a significant increased risk of endometrial cancer (cancer of the womb). This is reduced by using a progesterone/progestogen in a combined HRT but the risk is not completely removed and sequential HRT in particular has a very small increased risk of endometrial cancer if given for longer than 5 years.