Serum concentrations of carboxyl-terminal propeptide of type I procollagen, amino-terminal propeptide of type III procollagen, cross-linked carboxyl-terminal telopeptide of type I collagen, and their interrelationships in schoolchildren.

We report pediatric age- and sex-specific 95% reference intervals for procollagen type I C-terminal propeptide (PICP), the cross-linked C-terminal telopeptide of type I collagen (ICTP), and procollagen type III N-terminal propeptide (P3NP), measured in plasma from 302 schoolchildren (156 boys, 146 girls) ages 4-19 years. All three markers displayed a significant variation with age (ANOVA P < or = 0.0015). PICP showed no detectable increase during adolescence for either sex, but decreased towards adult concentrations after the age of puberty, with an earlier decrease for girls than for boys (P < 0.01). ICTP and P3NP both increased in pubertal-aged children (P < 0.05), with an earlier increase in girls than in boys (P < 0.05), before decreasing towards adult concentrations (P < 0.01). All three collagen markers were highly correlated with one another (P < 0.001). The patterns observed mirrored the childhood growth curve and reflected the high turnover of bone and soft tissue during childhood growth.