Biochemical markers of bone turnover and the volume and the density of bone in children at different stages of sexual development.

Bone mass and biochemical markers of bone turnover increase significantly during puberty. We studied the possible relationships between markers of bone formation and bone resorption and increases in skeletal size, bone volume, and bone density in healthy children at different stages of sexual development. Serum concentrations of bone specific alkaline phosphatase (BALP) and osteocalcin (bone Gla protein, BGP), urinary levels of pyridinoline (Pyr) and deoxypyridinoline (Dpyr) and computed tomography (CT) measurements of the cross-sectional areas of the vertebrae and the femurs, the apparent density of cancellous bone in the vertebrae, and the volume and the material density of cortical bone in the femurs were determined in 126 boys and 143 girls, ages 7-18 years. Serum levels of BALP and BGP and urinary concentrations of Pyr and Dpyr peaked in early puberty and were lowest in the later stages of puberty. CT measurements for the cross-sectional areas of the vertebrae and the femurs, the femoral cortical bone areas, and the apparent density of cancellous bone increased in all children during puberty, while values for material bone density did not change significantly with the stage of sexual development. BALP and BGP showed significant inverse correlations with the material density of bone (r = -0.23 and -0.24, respectively), but no association with bone volume in the appendicular or axial skeleton. In contrast, Pyr and Dpyr correlated with femoral cross-sectional area (r = -0.24 and -0.33, respectively) and cortical bone area (r = -0.29 and -0.33, respectively), and with the apparent density of vertebral cancellous bone (r = -0.26 and -0.19, respectively), but not with the material density of bone. We conclude that, during puberty, there is a differential association between the two components of bone mass and the markers of bone formation and bone resorption; while markers of bone formation are related to the material density of bone, markers of bone resorption are related to the volume of bone.