Early skeletal and biochemical alterations in pediatric chronic kidney disease

Background and objectives The relationship between parathyroid hormone, fibroblast growth factor 23 (FGF-23), and indices of bone turnover and mineralization in children with early CKD is unknown; thus, this study characterizes the features of renal osteodystrophy and their relationship to biochemical markers of mineral metabolism. Design, setting, participants, & measurements Fifty-two patients 2-21 years of age with predialysis CKD underwent tetracycline-labeled bone biopsy. Anthropomorphic measurements and biochemical values were obtained at the time of biopsy. Results Serum phosphorus levels were increased in 4% of patients with stage 3 CKD and 43% of those with stage 4/5 CKD. Parathyroid hormone concentrations were elevated in 36% of patients with stage 2, 71% with stage 3, and 93% with stage 4/5 CKD, whereas FGF-23 values were elevated in 81% of all patients, regardless of CKD stage. Bone turnover was normal in all patients with stage 2, but was increased in 13% with stage 3 and 29% with stage 4/5 CKD. Defective mineralization was present in 29% of patients with stage 2, 42% with stage 3, and 79% with stage 4/5 CKD. Defective skeletal mineralization was associated with lower serum calcium levels and increased parathyroid hormone concentrations. Conclusions Elevated circulating FGF-23 levels and defects in skeletal mineralization early in the course of CKD suggestthat factors other than the traditional markers of mineral deficiencyplaya crucial role in the development of renal bone disease.