Serum sex hormones and breast cancer risk factors in postmenopausal women

Postmenopausal women with elevated serum estrogens and androgens are at an increased risk of breast cancer. We evaluated associations of serum estrogen and androgen levels with age, anthropometry, and reproductive history to assess whether these characteristics could potentially modify breast cancer risk through hormonal mechanisms. A cross-sectional study was conducted among 133 postmenopausal women who donated blood to the serum bank (Columbia, MO) and served as controls in a previous prospective nested case control study of serum hormones and breast cancer risk. Standard regression methods were used to calculate adjusted means and test for trends in relationships of serum hormone concentrations with breast cancer risk factors. All analyses were performed on the log(e) scale, and all models included assay batch, date, and time of blood collection. Serum levels of estradiol, non-sex hormone binding globulin bound estradiol, estrone, estrone sulfate, and testosterone increased significantly with increasing body mass index (BMI), whereas sex hormone binding globulin levels decreased. After adjusting for BMI, milliparous women tended to have higher testosterone levels compared with parous women (P = 0.05), but there was no evidence of a trend of decreasing testosterone with increasing parity. Dehydroepiandrosterone, its sulfate, and androstenediol decreased significantly with increasing age. Although BMI and parity could potentially modify breast cancer risk through hormonal mechanisms, age-related increases in breast cancer incidence do not appear to be mediated through changes in serum levels of the hormones evaluated.