Collagen‐derived markers of bone metabolism in osteogenesis imperfecta

Abstract

Markers of bone formation [C‐terminal and N‐terminal propeptides of procollagen I (PICP, PINP), osteocalcin and alkaline phosphatase] and bone resorption [C‐terminal cross‐linked telopeptide of collagen I (ICTP) and hydroxypyridinium cross‐links, pyridinoline (Pyr) and deoxypyridinoline (Dpyr)] were measured in 78 osteogenesis imperfecta (OI) patients to investigate bone metabolism in vivo and relate marker concentrations to phenotype and in vitro collagen I defects, as shown by sodium dodecyl sulphate ‐polyacrylamide gel electrophoresis (SDS‐PAGE). PICP and PINP were generally low, and the serum levels were lower in all children and adults with mild OI and a quantitative collagen defect than in patients with severe OI and a qualitative collagen I defect. ICTP, Pyr and Dpyr were generally normal or reduced, but elevated in severely affected adults with a qualitative collagen I defect. The in vivo findings correlated with in vitro results of collagen I SDS‐PAGE. Bone turnover is reduced in OI children and mildly affected OI adults, whereas bone resorption is elevated in severely affected adults. These findings may prove helpful for diagnosis and decision‐making regarding therapy in OI.