Bone Abstracts

Objectives: To determine any relationship of serum concentrations of osteoprotegerin (OPG), sRANKL and sRANKL:OPG ratio with idiopathic hypercalciuria (IH) in children, as there is some evidence of increased bone resorption in these patients.

Methods: In a prospective study, twenty four children of median age 6.5 years (range 2.3–16.4) with IH (five had urolithiasis and two nephrocalcinosis) were examined at the time of diagnosis and after 3 months of salt free and adequate Ca diet. Clinically healthy children (n=46) matched for age, sex and season were used as controls (median 8.0 years, range 1.8–16.3). sRANKL (total), OPG, 25(OH)D, and 1.25(OH)₂D, PTH, Ca, Pi, osteocalcin (N-MID OC), ALP and CTX-Crosslaps were determined in serum and Ca, creatinine, oxalate and citrate in urine. Height was recorded and BMI Z-score was assessed.

Results: The BMI Z-score was lower in patients than controls (−0.425±0.641 vs +0.106±1.0, P=0.016), but height did not differ. Although urinary Ca excretion (24 hCa and UCa/UCr) decreased at 3 months (24 hUCa: 6.29±2.0 vs 5.19±2.3 mg/kg, P=0.06; UCa/UCr: 0.30±0.19 vs 0.21±0.12 mg/mg, P=0.014) on average it had not reached control values (2.14±1.08, P<0.0001; 0.10±0.06, P=0.0003). Ucitrate/UCr, UCa/UCitrate and 24 h oxalate did not differ in patients before and after diet or compared to controls. No significant differences were found for serum Ca, Pi, 25OHD, 1.25(OH)₂D, PTH, osteocalcin, ALP, OPG and sRANKL or for the sRANKL:OPG ratio. Only serum concentrations of CTX-Crosslaps were significantly higher in both patient samples (1.63±0.67, P<0.02; 1.56±0.45, P<0.05 than controls (1.24±0.56 pmol/l).

Conclusion: No evident changes in the serum cytokines OPG and sRANKL were noted in children with IH. However, growth might have been affected by increased bone resorption, as indicated by the higher levels of serum CTX-Crosslaps and unaffected formation, since osteocalcin was not found different from controls. Hence, an autocrine role of the above cytokines cannot be excluded.