title: Bone Density and Timing of Puberty in a Longitudinal Study of Girls.
abstract: OBJECTIVE
  Primary: To examine the relationship between relative timing of puberty with bone mineral density (BMD) in a group of adolescent girls; Secondary: To determine if family history of breast cancer was associated with bone mineral density.
  
  
  METHODS
  Longitudinal study of girls recruited between 6 and 7 years of age seen every 6 months for 5 years, and subsequently seen annually. BMD of the lumbar spine was measured by dual-energy X-ray absorptiometry (DXA) at mean age of 12.5 years; age- and race-specific Z-scores (BMDz) were calculated. Age of pubertal onset was determined by the first occurrence of breast stage 2, and participants were categorized into race-specific early, on-time and late puberty onset groups.
  
  
  METHODS
  BMDz by timing of pubertal onset, and by family history of breast cancer.
  
  
  RESULTS
  DXA scans were performed on 227 study participants, and a second scan was performed on 114 participants 2 years later. Age of onset of puberty was inversely correlated with BMDz, r = -0.31 (P < .0001). There was no association between BMDz and family history of breast cancer.
  
  
  CONCLUSIONS
  Earlier timing of puberty was associated with higher BMD. The high shared variance of BMD and timing of pubertal onset implies an underlying biologic basis.
authors.affiliation: University of Cincinnati College of Medicine, Cincinnati, OH.
authors.forename: Ashley M
authors.initials: AM
authors.lastname: Cattran
authors.affiliation: Division of General and Community Pediatrics, Cincinnati Children's Hospital Medical Center; and Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH.
authors.forename: Heidi J
authors.initials: HJ
authors.lastname: Kalkwarf
authors.affiliation: Department of Environmental Health, University of Cincinnati College of Medicine, Cincinnati, OH.
authors.forename: Susan M
authors.initials: SM
authors.lastname: Pinney
authors.affiliation: Division of Biostatistics and Epidemiology, Cincinnati Children's Hospital Medical Center; and Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH.
authors.forename: Bin
authors.initials: B
authors.lastname: Huang
authors.affiliation: Division of Adolescent and Transition Medicine, Cincinnati Children's Hospital Medical Center; and Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH. Electronic address: frank.biro@cchmc.org.
authors.forename: Frank M
authors.initials: FM
authors.lastname: Biro
mesh_terms: D015502:Absorptiometry, Photon; D000293:Adolescent; D015519:Bone Density; D001943:Breast Neoplasms / Q000235:genetics / Q000503:physiopathology; D002648:Child; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000502:physiology; D011627:Puberty
keywords: Bone density; Breast cancer; Puberty