Circulating levels of sex hormones and their relation to risk factors for breast cancer: a cross-sectional study in 1092 pre- and postmenopausal women (United Kingdom)

Objective: To investigate the relationships between plasma concentrations o f sex hormones and risk factors for breast cancer. Methods: We investigated the relationship of plasma concentrations of estra diol, progesterone, follicle-stimulating hormone (FSH), luteinizing hormone (LH) and sex hormone-binding globulin (SHBG) with breast cancer risk facto rs in 636 premenopausal and 456 postmenopausal women. Risk factor data were obtained from questionnaires and hormone concentrations measured by immuno assays; variations in geometric means were compared using analysis of covar iance. Results: SHBG decreased with increasing body mass index and increasing wais t-hip ratio both in pre- and postmenopausal women. In postmenopausal women only, estradiol increased with increasing body mass index. In premenopausal women, estradiol decreased with increasing physical activity, estradiol wa s higher in current than in ex- and non-smokers, and FSH decreased with inc reasing alcohol intake. No associations were observed between sex hormones and age at menarche, parity, age at menopause, and previous use of oral con traceptives in either pre- or postmenopausal women. Conclusions: Certain factors such as obesity and perhaps waist-hip ratio, p hysical activity and alcohol consumption, but probably not age at menarche and parity, may mediate their effects on breast cancer risk by changing cir culating concentrations of sex hormones.