title: Racial differences in cortical bone and their relationship to biochemical variables in Black and White children in the early stages of puberty.
abstract: Osteoporotic fracture rates differ according to race with Blacks having up to half the rate of Whites. The current study demonstrates that racial divergence in cortical bone properties develops in early childhood despite lower serum 25-hydroxyvitamin D in Blacks.
  
  
  BACKGROUND
  Racial differences in bone structure likely have roots in childhood as bone size develops predominantly during growth. This study aimed to compare cortical bone health within the tibial diaphysis of Black and White children in the early stages of puberty and explore the contributions of biochemical variables in explaining racial variation in cortical bone properties.
  
  
  METHODS
  A cross-sectional study was performed comparing peripheral quantitative computed tomography-derived cortical bone measures of the tibial diaphysis and biochemical variables in 314 participants (n = 155 males; n = 164 Blacks) in the early stages of puberty.
  
  
  RESULTS
  Blacks had greater cortical volumetric bone mineral density, mass, and size compared to Whites (all p < 0.01), contributing to Blacks having 17.0 % greater tibial strength (polar strength-strain index (SSIP)) (p < 0.001). Turnover markers indicated that Blacks had higher bone formation (osteocalcin (OC) and bone-specific alkaline phosphatase) and lower bone resorption (N-terminal telopeptide) than Whites (all p < 0.01). Blacks also had lower 25-hydroxyvitamin D (25(OH)D) and higher 1,25-dihydroxyvitamin D (1,25(OH)2D) and parathyroid hormone (PTH) (all p < 0.05). There were no correlations between tibial bone properties and 25(OH)D and PTH in Whites (all p ≥ 0.10); however, SSIP was negatively and positively correlated with 25(OH)D and PTH in Blacks, respectively (all p ≤ 0.02). Variation in bone cross-sectional area and SSIP attributable to race was partially explained by tibial length, 25(OH)D/PTH, and OC.
  
  
  CONCLUSIONS
  Divergence in tibial cortical bone properties between Blacks and Whites is established by the early stages of puberty with the enhanced cortical bone properties in Black children possibly being explained by higher PTH and OC.
authors.affiliation: Center for Translational Musculoskeletal Research and Department of Physical Therapy, School of Health and Rehabilitation Sciences, Indiana University, 1140 W. Michigan St., CF-326, Indianapolis, IN 46202, USA. stwarden@iupui.edu
authors.forename: S J
authors.initials: SJ
authors.lastname: Warden
authors.forename: K M
authors.initials: KM
authors.lastname: Hill
authors.forename: A J
authors.initials: AJ
authors.lastname: Ferira
authors.forename: E M
authors.initials: EM
authors.lastname: Laing
authors.forename: B R
authors.initials: BR
authors.lastname: Martin
authors.forename: D B
authors.initials: DB
authors.lastname: Hausman
authors.forename: C M
authors.initials: CM
authors.lastname: Weaver
authors.forename: M
authors.initials: M
authors.lastname: Peacock
authors.forename: R D
authors.initials: RD
authors.lastname: Lewis
mesh_terms: D000293:Adolescent; D000886:Anthropometry / Q000379:methods; D044383:Black People / Q000706:statistics & numerical data*; D001823:Body Composition; D015519:Bone Density / Q000502:physiology*; D002648:Child; D003430:Cross-Sectional Studies; D018483:Diaphyses / Q000000981:diagnostic imaging / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D015675:Osteocalcin / Q000097:blood; D010281:Parathyroid Hormone / Q000097:blood; D011627:Puberty / Q000097:blood / Q000208:ethnology* / Q000502:physiology; D013977:Tibia / Q000000981:diagnostic imaging / Q000502:physiology*; D014057:Tomography, X-Ray Computed / Q000379:methods; D014807:Vitamin D / Q000031:analogs & derivatives / Q000097:blood; D044465:White People / Q000706:statistics & numerical data*
chemical_list: D010281:Parathyroid Hormone; D015675:Osteocalcin; D014807:Vitamin D; C104450:25-hydroxyvitamin D