title: Objective habitual physical activity and estradiol levels in obese Latina adolescents.
abstract: BACKGROUND
  Lifetime physical activity (PA) is associated with decreased breast cancer (BC) risk; reports suggest that PA during adolescence contributes strongly to this relationship. PA lowers production of sex hormones, specifically estradiol, or decreases insulin resistance (IR), thereby lowering risk. Overweight Latina adolescents are insulin resistant and exhibit low levels of PA, potentially increasing their future BC risk.
  
  
  METHODS
  37 obese Latina adolescents (15.7 ± 1.1 yrs) provided measures of PA using accelerometry; plasma follicular phase estradiol, sex-hormone binding globulin, total and free testosterone, dehydroepiandrosterone-sulfate (DHEAS); IR using HOMA-IR; and body composition via DEXA. Partial correlations and stepwise linear regressions assessed cross-sectional relationships between sex hormones, IR and PA. Body composition, and age were included a priori as covariates.
  
  
  RESULTS
  Estradiol was negatively associated with accelerometer counts per minute (CPM; r = -0.4; P = .02), percent time spent in moderate PA (%MPA; r = -0.5; P = .006), and percent time in moderate or vigorous PA (%MVPA; r = -0.5; P = .007). DHEAS was positively associated with CPM (r = .4, P = .009), %MPA (r = .3, P = .04), and %MVPA (r = .3, P = .04). Other sex hormones and IR were not associated with PA measures.
  
  
  CONCLUSIONS
  This study is the first to show that higher habitual PA was inversely associated with estradiol in obese adolescents.
authors.affiliation: Dept of Preventive Medicine, University of Southern California, Los Angeles, CA, USA.
authors.forename: Lauren E
authors.initials: LE
authors.lastname: Gyllenhammer
authors.forename: Amanda K
authors.initials: AK
authors.lastname: Vanni
authors.forename: Courtney E
authors.initials: CE
authors.lastname: Byrd-Williams
authors.forename: Marc
authors.initials: M
authors.lastname: Kalan
authors.forename: Leslie
authors.initials: L
authors.lastname: Bernstein
authors.forename: Jaimie N
authors.initials: JN
authors.lastname: Davis
mesh_terms: D061725:Accelerometry; D000293:Adolescent; D001786:Blood Glucose; D015992:Body Mass Index; D001837:Body Weights and Measures; D001943:Breast Neoplasms / Q000097:blood / Q000208:ethnology; D003430:Cross-Sectional Studies; D019314:Dehydroepiandrosterone Sulfate / Q000097:blood; D004958:Estradiol / Q000097:blood*; D015444:Exercise / Q000502:physiology*; D005260:Female; D006630:Hispanic or Latino; D006801:Humans; D007333:Insulin Resistance / Q000502:physiology; D009765:Obesity / Q000097:blood* / Q000208:ethnology / Q000628:therapy*; D012306:Risk; D012738:Sex Hormone-Binding Globulin / Q000032:analysis; D013739:Testosterone / Q000097:blood
chemical_list: D001786:Blood Glucose; D012738:Sex Hormone-Binding Globulin; D013739:Testosterone; D004958:Estradiol; D019314:Dehydroepiandrosterone Sulfate