Effects of aerobic exercise training on estrogen metabolism in premenopausal women: A randomized controlled trial

Background: Regular physical activity may alter estrogen metabolism, a proposed biomarker of breast cancer risk, by shifting metabolism to favor production of 2-hydroxyestrone (2-OHE1). Few studies, however, have examined this question using a randomized controlled trial. Purpose: To examine the effects of 12 weeks of aerobic exercise training on 2-OHE1 and 16 alpha-hydroxyestrone (16 alpha-OHE1) in premenopausal women. Methods: Participants were healthy, regularly menstruating, Caucasian women, 20 to 35 years, body mass index of 18 to 29.9, not using pharmacologic contraceptives, with average or below average fitness [maximal oxygen consumption (VO2max), < 40 mL/kg/min]. Following a baseline menstrual cycle, participants (N = 32), were randomly assigned to a 12-week aerobic exercise training intervention (n = 17) or usual lifestyle (n = 15). Height, body mass, body composition by dual-energy X-ray absorptiometry, and VO2max were measured at baseline and following the intervention. Urine samples were collected in the luteal phase of four consecutive menstrual cycles. Results: The exercise group increased VO2max by 14% and had significant, although modest, improvements in fat and lean body mass. No significant between-group differences were observed, however, for the changes in 2-OHE1 (P = 0.944), 16 alpha-OHE1 (P = 0.411), or the ratio of 2-OHE1 to 16 alpha-OHE1 (P = 0.317). At baseline, there was an inverse association between body fat and 2-OHE1 to 16 alpha-OHE1 ratio (r = -0.40; P = 0.044); however, it was the change in lean body mass over the intervention that was positively associated with a change in 2-OHE1 to 16 alpha-OHE1 ratio (r = 0.43; P = 0.015). Conclusions: A 12-week aerobic exercise training intervention significantly improved aerobic fitness and body composition but did not alter estrogen metabolism in premenopausal women. Interestingly, an increase in lean body mass was associated with a favorable change in 2-OHE1 to 16 alpha-OHE1 ratio.