title: Effects of aerobic exercise training on estrogen metabolism in premenopausal women: a randomized controlled trial.
abstract: 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.
  
  
  OBJECTIVE
  To examine the effects of 12 weeks of aerobic exercise training on 2-OHE1 and 16alpha-hydroxyestrone (16alpha-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 (VO(2max)), <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 VO(2max) 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 VO(2max) 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), 16alpha-OHE1 (P = 0.411), or the ratio of 2-OHE1 to 16alpha-OHE1 (P = 0.317). At baseline, there was an inverse association between body fat and 2-OHE1 to 16alpha-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 16alpha-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 16alpha-OHE1 ratio.
authors.affiliation: E-488 Van Vliet Centre, Faculty of Physical Education and Recreation, University of Alberta, Edmonton, Alberta, Canada T6G 2H9.
authors.forename: Kristin L
authors.initials: KL
authors.lastname: Campbell
authors.forename: Kim C
authors.initials: KC
authors.lastname: Westerlind
authors.forename: Vicki J
authors.initials: VJ
authors.lastname: Harber
authors.forename: Gordon J
authors.initials: GJ
authors.lastname: Bell
authors.forename: John R
authors.initials: JR
authors.lastname: Mackey
authors.forename: Kerry S
authors.initials: KS
authors.lastname: Courneya
mesh_terms: D015502:Absorptiometry, Photon; D000328:Adult; D000416:Alberta; D000704:Analysis of Variance; D001823:Body Composition; D001827:Body Height; D015992:Body Mass Index; D004032:Diet; D004797:Enzyme-Linked Immunosorbent Assay; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D006894:Hydroxyestrones / Q000378:metabolism*; D010101:Oxygen Consumption / Q000502:physiology; D017697:Premenopause
chemical_list: D006894:Hydroxyestrones