title: Bone mineral density in postmenarchal adolescent girls in the United States: associated biopsychosocial variables and bone turnover markers.
abstract: OBJECTIVE
  During adolescence, bone formation prevails over resorption, resulting in accumulation of 40% of peak bone mass throughout this time period. Although multiple studies have explored bone mass accrual during the early stages of puberty, less is known about factors that may influence bone accrual during later years of adolescence. In the present cross-sectional study we examined relationships among bone mineral density (BMD) and demographic factors, behavioral variables, and bone metabolism markers in postmenarchal adolescent girls.
  
  
  METHODS
  The population was comprised of 389 healthy postmenarchal adolescent girls aged 11-18 years, who were recruited into a prospective study of the effect of depot medroxyprogesterone acetate (DMPA) on bone health in adolescents. At the baseline visit, investigators collected demographic, reproductive health, and lifestyle data, and performed a complete physical examination. Body mass index (BMI) was calculated. Before study initiation, BMD at the lumbar spine, total hip, and femoral neck was measured by dual-energy X-ray absorptiometry (DXA), and markers of bone metabolism (serum bone-specific alkaline phosphatase [BAP], serum osteocalcin, and urinary N-telopeptide [uNTX]) were measured. The baseline data from this study were analyzed to evaluate possible correlates of BMD in postmenarchal adolescent girls. Potential associations between BMD values and other parameters were assessed by analysis of variance and Pearson's correlation coefficient.
  
  
  RESULTS
  Participants enrolled in the study had a mean (+/- SD) chronological age of 14.9 +/-1.7 years (range 11-18), mean gynecologic age of 39.9 +/-23.0 months (range 1-120) postmenarche, and mean BMI of 23.5 +/-4.6 kg/m(2) (range 16.0-42.2). Racial/ethnic distribution was 46% African American, 35% Caucasian, and 19% other races; 9% had previously been pregnant. Positive correlations were observed between lumbar spine BMD and chronological age (r = .301, p < .0001), gynecologic age (r = .349, p < .0001), and BMI (r = .371, p < .0001). Total hip and femoral neck BMD values were significantly higher (p < .05 and p < .05, respectively) in African American participants compared with non-African American participants. Previous history of pregnancy was significantly associated with a lower BMD at the lumbar spine (p < .0001) and the total hip (p < .01) when compared with the BMD of adolescents who had never been pregnant. Cigarette smoking and alcohol use were not associated with significant differences in BMD. Negative correlations were observed between gynecologic age and the levels of BAP (r = -.564, p < .0001), osteocalcin (r = -.349, p < .0001), and uNTX (r = -.281, p < .0001), and between lumbar spine BMD and BAP (r = -.363, p < .0001), osteocalcin (r = -.129, p < .05), and uNTX (r = -.202, p < .001) levels.
  
  
  CONCLUSIONS
  Our data demonstrate that chronological age, gynecologic age, race/ethnicity, BMI, and previous history of pregnancy are markedly associated with BMD in postmenarchal adolescent girls. Bone accretion in the postmenarchal years continues in the face of a slowdown in bone turnover during this time period.
authors.affiliation: Hasbro Children's Hospital and Brown University, Providence, Rhode Island 02903, USA. zharel@lifespan.org
authors.forename: Zeev
authors.initials: Z
authors.lastname: Harel
authors.forename: Melanie
authors.initials: M
authors.lastname: Gold
authors.forename: Barbara
authors.initials: B
authors.lastname: Cromer
authors.forename: Ann
authors.initials: A
authors.lastname: Bruner
authors.forename: Margaret
authors.initials: M
authors.lastname: Stager
authors.forename: Laura
authors.initials: L
authors.lastname: Bachrach
authors.forename: Kevin
authors.initials: K
authors.lastname: Wolter
authors.forename: Carol
authors.initials: C
authors.lastname: Reid
authors.forename: Paige
authors.initials: P
authors.lastname: Hertweck
authors.forename: Anita
authors.initials: A
authors.lastname: Nelson
authors.forename: Dorothy
authors.initials: D
authors.lastname: Nelson
authors.forename: Susan
authors.initials: S
authors.lastname: Coupey
authors.forename: Christine
authors.initials: C
authors.lastname: Johnson
authors.forename: Ronald
authors.initials: R
authors.lastname: Burkman
authors.forename: Henry
authors.initials: H
authors.lastname: Bone
mesh_terms: D000293:Adolescent; D000367:Age Factors; D000704:Analysis of Variance; D015415:Biomarkers; D015992:Body Mass Index; D015519:Bone Density; D001842:Bone and Bones / Q000378:metabolism*; D002648:Child; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008019:Life Style; D017584:Reproductive History; D012959:Socioeconomic Factors; D014481:United States
chemical_list: D015415:Biomarkers