Bone turnover markers and bone mineral density in children with haemophilia

During childhood growth, bone undergoes modelling involving separate osteoblastic and osteoclastic processes. Markers of bone turnover circulate at high concentrations, parallel the childhood growth curve and correlate with height velocity. The aim of this study was to compare serum markers of bone turnover in children with haemophilia and normal bone mineral density (BMD) vs. those with low BMD. In a cross-sectional study, 69 children with haemophilia were evaluated, 45 children with normal spine BMD vs. 24 with low BMD. Lumbar spine BMD was determined using dual X-ray absorptiometry and Z-scores were calculated. Serum samples of markers of bone turnover, osteocalcin (bone formation) and C-telopeptide of type I collagen (bone resorption) were measured using ELISA. The mean BMD (g cm(-2)) in the normal group was 0.656 +/- 0.15 vs. 0.558 +/- 0.12 in those with low BMD (P = 0.007), osteocalcin levels in children with normal BMD were 9.29 +/- 4.97 vs. 7.06 +/- 2.17 ng mu L(-1) in the low BMD group (P = 0.012). C-telopeptide levels in the normal group were 1.06 +/- 1.4 vs. 0.74 +/- 0.3 ng mL(-1) in the low BMD group (P = 0.169). Our results showed that low osteocalcin levels predominated in the group with low BMD, which indicates a diminished osteoblastic bone formation activity while there were no differences with regard to bone resorption markers. Moreover, osteocalcin levels explain 10% of the variation of lumbar spine Z-score.