Biochemical markers of bone metabolism: Application to understanding bone remodeling in children and adolescents

Markers of bone remodeling have been developed that provide biochemical indices that reflect changes in the rates of bone formation, resorption, and mineralization. These processes are important determinants of bone metabolism, and indicators that correspond to these processes can provide clinically relevant information. Until recently, the best way to measure parameters of bone metabolism was to perform a bone biopsy after administration of two courses of tetracycline. Bone markers offer significant potential advantages over bone biopsy. Some of these markers are protein fragments that are generated during metabolism of type I collagen, the major structural protein of bone, and are formed as this collagen is synthesized or degraded. Other markers, such as osteocalcin and alkaline phosphatase, are released from osteoblasts during bone formation. Although these markers have found significant utility in the evaluation of adults with metabolic bone diseases, their application in children has been limited due to great variability in normal ranges that reflect the changes in skeletal metabolism induced by age, growth rate, gender, and pubertal state.