Naturally high oestrogen levels may lower women's bowel cancer risk

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Researchers from Imperial College London studied a group of 1,200 women from the Women’s Health Initiative clinical trial [2] to look at the levels of sex hormones, like oestrogen, in their blood and whether they went on to develop bowel cancer.

In the UK one in 19 women will develop bowel cancer in their lifetime.

Women with the highest levels of oestrone, the main form of oestrogen after menopause, had a 56 per cent lower risk of developing the disease, compared with women with the lowest levels.

They also found that women with the highest levels of sex hormone-binding globulin (SHBG) – a protein which carries sex hormones around the body – were two and a half times more likely to develop bowel cancer than women with the lowest levels.

This may be because SHBG binds and inactivates hormones so they cannot act on the body.

The researchers only studied women who were not receiving hormone replacement therapy (HRT) so they could find how natural levels of the hormones affected cancer risks.

Bowel cancer is the fourth most common cancer in the UK, with around 41,600 people – and around 18,400 women - diagnosed with the disease each year. Around 95 per cent of cases are in people aged 50 and over.

Lead author Dr Neil Murphy, epidemiologist from Imperial College London, said: “This important research is the first time we’ve seen strong links between sex hormones, SHBG and the risk of developing bowel cancer – which raises a lot of questions. We need more research to look into these links more closely, but our results offer intriguing insights into the biology of this common cancer.

“By tracking older women’s hormone levels we could find those at higher and lower risk of bowel cancer, and we may one day be able to tailor the amount of screening women are offered based on this information.”

Professor Matt Seymour, NCRI clinical research director, said: “Bowel cancer survival has doubled in the last 40 years thanks to scientists translating their findings into better treatment. But much more needs to be done. And research like this which aims to understand the biology of the disease and the role hormones play could reveal vital new clues to help doctors and scientists tackle the disease.”

The work was funded by the US National Institutes of Health and the National Heart, Lung, and Blood Institute.

Reference

1. Murphy N, Strickler H et al. A prospective evaluation of endogenous sex hormone levels and colorectal cancer risk in postmenopausal women. Journal of the National Cancer Institute 2015. doi: 10.1093/jnci/djv210
2. Women’s Health Initiative. Department of Health and Human Services, National Institutes of Health.

klíčová slova: bowel cancer, oestrogen, oestrone, sex hormone-binding globulin (SHBG), hormone replacement therapy (HRT)