Sex hormone levels linked to colorectal cancer in post-menopausal women

Researchers have identified links between sex hormone levels in post-menopausal women and their risk of developing colorectal cancer.

A study, led by Imperial College London researchers Dr Neil Murphy and Dr Marc Gunter and published this month in the Journal of the National Cancer Institute , has showed that post-menopausal women who had naturally higher levels of the hormones estradiol and estrone were significantly less likely to develop colorectal cancer.

Conversely, the study also found that women with higher levels of sex hormone-binding globulin (SHBG) – a protein responsible for transporting sex hormones around the body – had a higher risk of developing this type of cancer.

Although colorectal cancer is the third most common cancer, with more than 1 million new patients diagnosed each year, women are statistically less likely to develop the disease than men, and it has been thought that female sex hormones might play a protective role.

So far, however, research into these ideas has proved inconclusive. The new research is the largest study to be carried out in this area and the results obtained strongly support the theory.

Working in collaboration with the Albert Einstein College of Medicine, in New York, the team studied blood samples from 1,203 women recruited into a long-term health study called the Women’s Health Initiative Clinical Trial Study.

The group included 401 women who developed colorectal cancer post-menopause, and 802 women in a control group. The sample selection did not include women who received hormone replacement therapy as their artificially elevated levels of sex hormones could have skewed the results.

Levels of estradiol and estrone were measured in each of the women and they were categorised in groups from high levels to low levels. Women who had the highest levels of these hormones were over 50 per cent less likely to develop colorectal cancer than women in the lowest level group. Women with higher levels of SHBG had a 2.5 fold higher risk of colorectal cancer than those with lower levels.

“Our work has shown strong links between levels of sex hormones and risk of developing colorectal cancer,” says Dr Neil Murphy of Imperial’s School of Public Health. “Because hormone replacement therapy is associated with increased risk of developing other cancers, we wouldn’t advocate using these drugs to protect against colorectal cancer. If future studies confirm our results, however, these findings could be useful as a means of risk stratifying women into high- and low-risk groups for colorectal cancer screening.”

Further research by the team will investigate whether the associations they have identified are replicated in larger study groups. They also plan to look at associations between sex hormones and colorectal cancer in other groups, including pre-menopausal women and men.

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

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Reference: "A Prospective Evaluation of Endogenous Sex
Hormone Levels and Colorectal Cancer Risk in
Postmenopausal Women," Journal of the National Cancer Institute, published online 1 August 2015. Authors: Neil Murphy, Howard D. Strickler, Frank Z. Stanczyk, Xiaonan Xue, Sylvia Wassertheil-Smoller, Thomas E. Rohan, Gloria Y. F. Ho, Garnet L. Anderson, John D. Potter, Marc J. Gunter.