Raised levels of several hormones can triple the risk of breast cancer in post-menopausal women, a study has shown.
Scientists looked at the combined effect of multiple sex and growth hormones on a woman’s cancer chances.
They found that one hormone at a higher level than normal increased the breast cancer risk by 10% compared with having no elevated hormones.
But the risk for women with five or six hormones at raised levels was doubled, while having seven or eight tripled the odds of getting cancer.
The US researchers compared levels of eight hormones in blood samples collected from 33,000 nurses aged 43 to 69.
The findings, published today in the journal Breast Cancer Research, showed that “ER positive” breast cancers with molecular receptors sensitive to oestrogen were the most influenced by hormone levels.
Study leader Dr Shelley Tworoger, from Brigham and Women’s Hospital in Boston, said: “Elevated oestrogens had the biggest effect on risk, especially for ER positive (oestrogen-sensitive) cancer. However, androgens, and prolactin also contribute to increasing risk of breast cancer.
“Our results suggest that models used to assess breast cancer risk could be improved by taking into account multiple sex hormone and growth hormone levels.”