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Objective: During adolescence, bone formation prevails over resorption, and accumulation of 40% of peak bone mass ensues throughout this time period. Multiple studies have explored bone mass accrual during the early stages of puberty, but less is understood concerning factors that may affect bone accrual during later years of adolescence. This cross-sectional study analyzed relationships among bone mineral density (BMD) and demographic characteristics, behavioral variables, and bone metabolism markers in postmenarchal adolescent girls. 
Method: The cohort comprised 389 healthy postmenarchal adolescent girls, aged 11 to 18 years, who were recruited into a prospective study of the effect of depot medroxyprogesterone acetate (DMPA) on bone health in adolescents. Investigators gathered demographic, reproductive health, and lifestyle data and performed a complete physical examination at baseline. Body mass index (BMI) was calculated. 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 prior to the study initiation. The baseline data from this study were examined to assess potential correlates of BMD in postmenarchal adolescent girls. Possible associations between BMD values and other parameters were evaluated by analysis of variance and Pearson’s correlation coefficient. Results: Subjects who entered the study had a mean (± SD) chronological age of 14.9 ± 1.7 years (range, 11–18), gynecologic age of 39.9 ± 23.0 months (range, 1–120) postmenarche, and BMI of 23.5 ± 4.6 kg/m2 (range, 16.0–42.2). Racial/ethnic distribution was 46% African American, 35% Caucasian, and 19% other races; 9% had 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 subjects relative to non–African American subjects. A history of pregnancy was significantly associated with a lower BMD at the lumbar spine (p < .0001) and the total hip (p < .01) relative to the BMD of adolescents who had never been pregnant. Alcohol use and cigarette smoking were not associated with significant differences in BMD. Negative correlations were seen 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: According to our data, in postmenarchal adolescent girls, chronological age, gynecologic age, race/ethnicity, BMI, and previous history of pregnancy are markedly associated with BMD. Bone accretion in the postmenarchal years continues as bone turnover slows during this time period.

Prim Care Companion J Clin Psychiatry 2007;9(3):244-249