It's not known exactly what causes womb cancer, although a number of things can increase your risk of developing the condition.
The risk of womb cancer increases with age. Most cases occur in women aged 40 to 74, with only 1% of cases being diagnosed in women under 40.
Oestrogen levels after the menopause
The risk of developing womb cancer is linked to the body's exposure to oestrogen.
Oestrogen is one of the hormones that regulates the reproductive system in women:
- oestrogen stimulates the release of eggs from your ovaries and causes the cells of the womb lining to divide
- progesterone gets the lining of your uterus ready to receive the egg from the ovaries
The levels of oestrogen and progesterone in your body are usually balanced. If oestrogen is not kept in check by progesterone, it can increase. This is called unopposed oestrogen.
After the menopause, the body stops producing progesterone.
However, there are still small amounts of oestrogen being produced.
This unopposed oestrogen causes the cells of the endometrium to divide, which can increase the risk of womb cancer.
Being overweight or obese
As oestrogen can be produced in fatty tissue, being overweight or obese increases the level of oestrogen in your body. This significantly increases your chances of developing womb cancer.
Women who are overweight are 3 times more likely to develop womb cancer compared with women who are a healthy weight.
Very obese women are 6 times more likely to develop womb cancer compared with women who are a healthy weight.
One way to assess if you are a healthy weight is to calculate your body mass index (BMI).
Women who have not had children are at a higher risk of womb cancer.
This may be because the higher levels of progesterone and lower levels of oestrogen that occur during pregnancy have a protective effect on the lining of the womb.
Women who take tamoxifen – a hormone treatment for breast cancer – can be at an increased risk of developing womb cancer.
However, this risk is outweighed by the benefits that tamoxifen provides in preventing breast cancer.
It's important to visit your GP if you're taking tamoxifen and experience any abnormal vaginal bleeding.
High levels of insulin
Conditions such as hyperinsulinaemia, where your body produces more insulin than normal, can increase the risk of tumours.
Polycystic ovary syndrome (PCOS)
Women with polycystic ovary syndrome (PCOS) are at a higher risk of developing womb cancer, as they have high levels of oestrogen in their bodies.
Women with PCOS have lots of cysts in their ovaries, which can cause symptoms such as irregular or light periods, or no periods at all, as well as problems getting pregnant, weight gain, acne and excessive hair growth (hirsutism).
Endometrial hyperplasia is when the lining of the womb becomes abnormally thicker.
Women with the condition may be at an increased risk of developing womb cancer.
Want to know more?
- Cancer Research UK: womb cancer risks and causes