title: Associations of birth weight and physical activity with sex steroids in preschool Japanese children.
abstract: OBJECTIVE
  We aimed to assess the association of body size at birth or physical activity with sex steroid levels, independent of body mass among young children.
  
  
  METHODS
  The cross-sectional study was conducted in 2006. Subjects were 230 boys and 198 girls, aged 3-6 years. Birth weight was based on parents' reports. Questions about physical activity focused on outdoor playtime. Urinary estrone, estradiol, testosterone, and 5-androstene-3β,17α diol (3β,17α-AED) levels were measured by liquid chromatography-electrospray ionization tandem mass spectrometry. Urinary dehydroepiandrosterone level was measured with a radioimmunoassay.
  
  
  RESULTS
  After adjustments for age and BMI, girls with lower birth weight had higher testosterone (trend p = 0.038) and 3β,17α-AED (trend p = 0.028). Girls with low birth weight and high birth weight had higher estrone (p = 0.014) and estradiol (p = 0.074) than those who had middle birth weight. Boys who were physically active had lower testosterone (p = 0.028) and 3β,17α-AED (p = 0.003) than those who were not active. Girls who were physically active had lower estrone (p = 0.015).
  
  
  CONCLUSIONS
  Sex steroid levels in childhood might be affected by body size at birth or by physical activity during childhood. These effects might differ by sex.
authors.affiliation: Department of Epidemiology and Preventive Medicine, Gifu University Graduate School of Medicine, Gifu 501-1194, Japan. dr_keiko@gifu-u.ac.jp
authors.forename: Keiko
authors.initials: K
authors.lastname: Wada
authors.forename: Kozue
authors.initials: K
authors.lastname: Nakamura
authors.forename: Yuya
authors.initials: Y
authors.lastname: Tamai
authors.forename: Michiko
authors.initials: M
authors.lastname: Tsuji
authors.forename: Takako
authors.initials: T
authors.lastname: Masue
authors.forename: Kyoko
authors.initials: K
authors.lastname: Ando
authors.forename: Chisato
authors.initials: C
authors.lastname: Nagata
mesh_terms: D001724:Birth Weight; D015992:Body Mass Index; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D005260:Female; D012739:Gonadal Steroid Hormones / Q000652:urine*; D006801:Humans; D007564:Japan; D008297:Male; D009043:Motor Activity
chemical_list: D012739:Gonadal Steroid Hormones