Sex hormone levels and breast density are independent risk factors for breast cancer in postmenopausal women, according to a study published in the Journal of the National Cancer Institute.

Breast density and hormone levels are both well-known predictors of breast cancer, but it is unclear whether hormone levels regulate breast density.

Rulla Tamimi, Sc.D., of Brigham and Women’s Hospital in Boston and colleagues measured breast density and estrogen and testosterone levels in postmenopausal women who later developed breast cancer and those who did not. They found that sex hormone levels and breast density are strongly and independently associated with breast cancer risk.

“Thus, levels of circulating sex steroid hormones and mammographic density may increase breast cancer risk through different mechanisms,” the authors write.

SOURCE:
Journal of the National Cancer Institute, July 24, 2007