Bone metabolism biomarkers, body weight, and bone age in healthy Brazilian male adolescents
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Eighty-seven male volunteers were grouped according to bone age (BA): 10-12 years (n=25), 13-15 years (n=36), and 16-18 years (n=26), and the following were recorded for each: weight (kg), height (m), BMI (kg/m(2)), calcium intake from three 24-h food recalls (mg/day), puberty evaluation by Tanner stages, bone biomarker (BB) evaluation, serum osteocalcin (OC), bone alkaline phosphatase (BAP), carboxyterminal telopeptide (S-CTx), and bone mineral density (BMD) evaluations by dual-energy X-ray absorptiometry (g.cm(2)) in the lumbar spine, proximal femur, and the whole body. BBs showed similar behaviors, and very high median values were observed for individuals aged 13-15 years (BAP=155.50 IU/L, OC=41.63 ng/mL, S-CTx=2.09 ng/mL). Lower median BB values were observed with advancing BA between 16 and 18 years (BAP=79.80 IU/L, OC=27.80 ng/mL, S-CTx=1.65 ng/mL). Stepwise multiple regression analysis showed body weight associated with BA as independent variables with greater determination power for S-CTx (r(2)=0.40) and OC (r(2)=0.21). For BAP, stepwise analysis showed body weight and whole-body BMD (r(2)=0.34). All predictive models showed significance (p<0.01). A high turnover for both bone formation and resorption biomarkers, particularly from 13 to 15 years of BA, were observed along with very low values in the 16-18 age range. Weight and BA were significant in determining predictive equations of OC and of S-CTx, whereas for BAP, weight and BMD of full body were selected.