By Jimmy Downs

Friday Jan 11, 2013 (foodconsumer.org) -- A new study in Breast Cancer Research and Treatment has confirmed a long-known fact that high plasma levels of sex hormones promote the development or growth of breast cancer in postmenopausal women.

High sex hormones make women look attractive to men (and some women too). But exposure to high levels of both endogenous and exogenous sex hormones can increase risk of breast cancer and other malignancies.

The current study led by X Zhang from Brigham and Women's Hospital and Harvard Medical School in Boston, MA, USA and colleagues shows that women in the highest quartile of levels of estradiol, free estradiol, testosterone, free testosterone, and dehydroepiandrosterone sulfate had their risk for breast cancer increased by 50 to 110%, compared with those in the lowest quartile.

The study finds also that sex hormone-binding globulin was inversely associated with risk of breast cancer, meaning that high sex hormone-binding globulin reduced the risk.

Data used in the study came from 707 cases of breast cancer and 1414 controls enrolled in the Nurses' Health Study. Blood samples were drawn in 1989-1990 and again in 2000-2002. 

ER+/PR+ breast cancer was found more sensitive to the influence of sex hormone estradiol than ER-/PR- breast cancer.  Those in the highest quartile of estradiol levels were at 180% increased risk for breast cancer, compared with 10% increase among those with .  Those who had highest amounts of testosterone were 80% more likely to develop breast cancer.

The researchers concluded "One measure of circulating sex hormones in postmenopausal women can predict risk of hormone receptor positive breast cancer for up to 16-20 years."