URINARY PYRIDINOLINE AND DEOXYPYRIDINOLINE EXCRETION IN CHILDREN

OBJECTIVE There are few data on urinary markers of collagen breakdown in children. We have determined a normal range for urinary pyridinolin e and deoxypyridinoline in children, assessed the variability in excre tion in individual children and examined the effect of GH treatment on the excretion of these collagen cross-links. DESIGN A cross-sectional study of a group of healthy children and sequential samples from chil dren receiving GH treatment. PATIENTS One hundred and nine healthy chi ldren aged 2-15 years, 8 healthy children aged 4-11 years and 4 childr en receiving GH treatment. MEASUREMENTS Total pyridinoline and deoxypy ridinoline excretion were measured by high performance liquid chromato graphy after initial acid hydrolysis and cellulose extraction steps. S erum parathyroid hormone was measured using a two-site immunoradiometr ic assay and urinary hydroxyproline by Ehrlich's reaction using a colo rimetric assay. Pyridinoline and deoxypyridinoline excretion were expr essed as a ratio against urine creatinine. RESULTS High excretion of p yridinoline (Pyr) and deoxypyridinoline (DPyr) was seen at all ages wi th no apparent relation to age (mean Pyr/Cr 115 nmol/mmol and DPyr/Cr 31 nmol/mmol). No correlation was found with serum parathyroid hormone or urinary hydroxyproline excretion. Marked day to day variation was seen in individual children. A progressive rise in excretion was seen in children receiving GH treatment with no significant correlation to height velocity. CONCLUSIONS There is a high excretion of the pyridini um cross-linking amino acids in children of all ages compared to adult s. However, a high variability exists in single morning urine samples which will limit the usefulness of these markers in growing children.