High hormone levels raise risk of breast cancer

Women past their menopause with high levels of estrogen and testosterone hormones are known to have an increased risk of breast cancer. According to a new study published in BioMed Central's open access journal Breast Cancer Research, the risk of breast cancer increased with the number of elevated hormones. After examining eight different sex and growth hormones researchers established that each additional elevated hormone level increased the risk of breast cancer by 16%. Investigators from the Brigham and Women's Hospital and Harvard Medical School obtained data from nurses' blood samples up to nine years before health information was recorded. The data included the women's breast cancer status and researchers matched diagnosed post-menopausal women with breast cancer to two controls of similar ages. The researchers individually linked the risk of breast cancer to the highest levels of circulating hormones, such as estrogens, i.e. estrone and estrogen, prolactin and androgens, i.e. testosterone, androtenedione, DHEA, or DHEA-sulfate, and discovered increased risks between 50 to 200%. They also discovered that the amount of different hormone levels that were above the normal level increased the risk even further, with the risk for women with one hormone level above normal being 10% higher. The risk doubled for those who had five or six elevated hormone levels and even tripled in women with seven or eight different hormone levels above normal. In women with ER positive disease all risks were slightly higher. Dr Shelley Tworoger, from Brigham and Women's Hospital explained:     "Elevated estrogens had the biggest effect on risk, especially for ER positive cancer. However, androgens, and prolactin also contribute to increasing risk of breast cancer.     These hormones are known to stimulate the growth of breast cancer cells in the lab and, while androgens can be converted to estrogen in the body, these hormones have also been found to stimulate cancer cell growth in the absence of ER.     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."