Hormones and cancer
Our bodies are full of hormones that tell our cells what to do. At high levels, these naturally-occurring hormones can increase our risk of cancer by encouraging cells to grow or divide more quickly than usual.
This section will discuss the links between hormones and cancer. You can find out about different sources of hormones and whether they affect your risk of cancer. These include:
What is a hormone?
Hormones are naturally occurring substances that are produced in specific parts of our bodies and act as chemical messengers. They travel through the blood to control the functions of other tissues and organs.
Some of the best known hormones are oestrogen and testosterone. These are known as ‘sex hormones’ and perform a variety of functions all around our bodies.
How do hormones affect our risk of cancer?
Because they have such important roles, the levels of hormones in our bodies is carefully controlled. If these are too high, they can make our cells grow and divide uncontrollably and stop them from dying when damaged. This can lead to cancer.
Testosterone. At the moment, it isn’t clear if high levels of testosterone in men increases the risk of prostate cancer. But we do know that prostate cancer cells depend on testosterone in order to grow.
Insulin also affects the levels of another group of similar hormones called insulin-like growth factors or IGFs. High levels of IGF-1 could increase the risk of prostate, breast and bowel cancers. Many scientists are studying the links between insulin, IGFs and cancer but at the moment, they are still unclear.
What affects our hormone levels?
Reproductive factors. A woman’s hormone levels change when she goes through her menstrual cycle or has children. These ‘reproductive factors’ are linked to risks of hormone-related cancers, such as breast and womb cancer. They include:
- being pregnant
- having children
- the age at which a woman has her first child
- whether she breastfeeds and for how long
- the age at which she starts menstruating
- the age at which she goes through menopause
We will be adding more information about these reproductive factors and their links to cancer in the near future.
Lifestyle changes. Reproductive factors are very difficult to control. But this doesn’t mean that there is nothing you can do to prevent hormone-related cancers.
Maintaining a healthy bodyweight can help to keep hormone levels under control. This is especially important in women after the menopause, whose ovaries have stopped making hormones. When this happens, fat cells become the main hormone source.
There is also some evidence that drinking too much alcohol and not getting enough physical activity could increase a woman’s levels of oestrogen. This may be why these things also increase the risk of breast cancer.
External sources. Your body makes its own hormones but external sources can also raise or lower your hormone levels. These include:
- Hormone replacement therapy (HRT)
- The contraceptive Pill
- Environmental chemicals that mimic hormones
Drugs that lower hormone levels. Oestrogen and testosterone can fuel the growth of breast and prostate cancer cells respectively. So scientists have designed drugs to fight these cancers by lowering the levels of these hormones or blocking their action.
One of these drugs, tamoxifen, has greatly improved survival rates for breast cancer. It works by blocking oestrogen from interacting with a partner protein, just like a piece of gum can stop a key from fitting in a lock.
Cancer Research UK is funding research to see if drugs that lower hormone levels could help to prevent breast cancer from occurring in the first place. These include tamoxifen and another drug called anastrozole that blocks oestrogen production. You can find more information about these drugs in our website CancerHelp UK.
Question about cancer? Contact our information nurse team