Bone metabolism biomarkers, body weight, and bone age in healthy Brazilian male adolescents.

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 x 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-CT x =2.09 ng/mL). Lower median BB values were observed with advancing BA between 16 and 18 years (BA P =79.80 IU/L, O C =27.80 ng/mL, S-CT x =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.