title: Timing of peak bone mass: discrepancies between CT and DXA.
abstract: BACKGROUND
  The time of life in which peak bone mass in the axial skeleton is attained has been the subject of considerable controversy, with estimates ranging from the time of sexual and skeletal maturity to the fifth decade of life.
  
  
  OBJECTIVE
  The objective was to examine whether dual energy x-ray absorptiometry (DXA) and computed tomography (CT) values for bone mass and bone density (BD) in the axial skeleton increase after sexual and skeletal maturity.
  
  
  METHODS
  Measurements of vertebral bone mineral density and bone mineral content (BMC) by DXA and vertebral BD and BMC by CT were obtained in 50 sexually and skeletally mature white females at baseline and 3 yr later. CT BMC values were calculated through analysis of vertebral volume in relation to density (BMC = vertebral volume x BD).
  
  
  RESULTS
  Although neither CT BD nor BMC measures changed with time, DXA bone mineral density and BMC values were significantly higher at follow-up (P < 0.0001). Despite strong correlations between DXA and CT bone measures, DXA yielded greater changes in bone values in 47 of 50 subjects.
  
  
  CONCLUSIONS
  Bone acquisition in the lumbar spine as measured by CT reaches its peak by sexual and skeletal maturity. In contrast, bone values by DXA continue to increase after puberty and cessation of longitudinal growth. Increases in DXA measures are likely a reflection of inhomogeneous changes in soft tissues around the spine or of disproportionate increases in the posterior elements of the vertebrae rather than of changes within the vertebral body.
authors.affiliation: Children's Hospital Los Angeles, Los Angeles, California 90027, USA.
authors.forename: Tishya A L
authors.initials: TA
authors.lastname: Wren
authors.forename: Paul S
authors.initials: PS
authors.lastname: Kim
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Janicka
authors.forename: Monique
authors.initials: M
authors.lastname: Sanchez
authors.forename: Vicente
authors.initials: V
authors.lastname: Gilsanz
mesh_terms: D015502:Absorptiometry, Photon; D000293:Adolescent; D000328:Adult; D000375:Aging / Q000502:physiology*; D015519:Bone Density; D001846:Bone Development / Q000502:physiology*; D005260:Female; D006801:Humans; D012741:Sexual Maturation / Q000502:physiology; D013997:Time Factors; D014057:Tomography, X-Ray Computed