Diurnal Variations in Serum and Urine Markers of Type I and Type III Collagen Turnover in Children

New serum and urine markers of type I and type III collagen turnover have recently been introduced in children. These markers include the formation markers of type I collagen turnover, serum N-terminal (PINP) and C-terminal (PICP) propeptides of type I procollagen, and serum N-terminal propeptide of type III procollagen (PIIINP), as well as the resorption markers serum cross-linked C-terminal telopeptide of type I collagen (ICTP) and urine cross-linked N-telopeptides of type I collagen (Ntx) and deoxypyridinoline (DPD) (1)(2)(3)(4)(5). The aim of the present study was to assess diurnal variations in serum PINP, PICP, ICTP, PIIINP, and urine DPD and Ntx in children. Two boys and five girls 10.4–14.4 years (mean, 12.2 years) were studied. One boy and three girls were in puberty. Height SD scores varied from −2.5 to 2.2 (mean, 0.6) and weight SD scores from −1.4 to 1.0 (mean, −0.4). The study was approved by the local ethics committee, and informed consent was obtained from all children and their parents. The first sample was urine collected from 2400 to 0800 on the morning of the day of investigation. Thereafter, urine was collected in 4-h intervals until …