A cross-sectional study on biochemical parameters of bone turnover and vitamin D metabolites in healthy dutch children and young adults

Aim: To provide reference data of biochemical markers of bone turnover and vitamin D metabolites for children and young adults. Methods: Blood samples were taken from 176 healthy Dutch children and young adults (age range 7.6-25.3 years) to assess serum calcium, alkaline phosphatase, inorganic phosphate, osteocalcin, collagen type I cross-linked N-telopeptide, N-terminal propeptide of type I procollagen, 25-hydroxyvitamin D₃, and 1,25-dihydroxyvitamin D₃ levels. Cross-linked telopeptide of type I collagen and carboxy-terminal propeptide of type I procollagen were assessed in 286 subjects (age range 1.4-25.3 years). Results: Calcium and vitamin D levels were independent of age. The peak concentrations for collagen type I cross-linked N-telopeptide, cross-linked telopeptide of type I collagen, carboxy-terminal propeptide of type I procollagen, N-terminal propeptide of type I procollagen, alkaline phosphatase, and osteocalcin were found during puberty, in girls approximately 2.5 years earlier than in boys. Strong correlations were found between the markers of bone turnover, while no correlation was found between the markers of bone turnover and bone mineral density measured by dual-energy X-ray absorptiometry. Conclusions: Single measurements of bone markers cannot predict bone density. Reference data according to gender, age, and Tanner stage are given which allow calculating standard deviation scores adjusted for age and gender.