Abstract
OBJECTIVES: To determine the effects of growth, maturation, and whole body bone mineral content (WB-BMC) accrual on biomarkers of bone formation (bone-specific alkaline phosphatase [BSAP]) and resorption (urine deoxypyridinoline/creatinine [DPD]) in healthy children and children with Crohn's disease. STUDY DESIGN: BSAP and DPD were measured at baseline, with growth and dual energy x-ray absorptiometry (DXA) WB-BMC measured at baseline and 6 months in 202 control subjects and 110 subjects with Crohn's disease, ages 5 to 21 years. Multivariable linear regression identified determinants of biomarkers in control subjects and subjects with Crohn's disease. RESULTS: In control subjects, BSAP and DPD were significantly and independently associated with sex, Tanner stage, WB-BMC, height velocity, and WB-BMC accrual rates; these covariates explained 77% to 80% of the variability in the bone biomarkers, respectively. Subjects with Crohn's disease had lower height-for-age (P < .001) and WB-BMC-for-height (P <.05) than control subjects. Crohn's disease was associated with lower BSAP (P < .001) and greater DPD (P < .001), independent of growth, maturation, baseline WB-BMC, and WB-BMC accrual, compared with control subjects. CONCLUSIONS: These data illustrate the potential confounding effects of growth and WB-BMC on bone metabolism biomarkers in children. After adjustment for these effects, Crohn's disease was associated with lower biomarkers of bone formation and greater bone resorption.