Original Article Increased bone resorption in HD patients: is it caused

Background. The receptor activator of nuclear factor kB ligand (RANKL), produced by osteoblasts/stromal cells, is a member of the RANK/RANKL/OPG system, which regulates bone resorption by osteoclasts. Since RANKL and osteoprotegerin (OPG) production in bone is influenced by parathyroid hormone (PTH), we measured serum RANKL and OPG concentrations in haemodialysis (HD) patients, who commonly hyper-secrete PTH. We aimed to determine if clinically demonstrated PTH-enhanced bone resorption is a consequence of increased RANKL synthesis. Methods. RANKL, OPG, osteocalcin, intact PTH, bone-specific alkaline phosphatase, tartrate-resistant acid phosphatase 5b and b-CrossLaps (CTx) were measured in blood samples from 80 HD patients and 50 age-matched controls. HD patients were stratified to tertiles according to their serum PTH levels: 29.3–103.0, 109.7–263.0 and 262.0–1700.0 pg/ml in the first, second and third tertiles, respectively. Results. Mean serum RANKL levels were 1.6 times higher in HD patients than in age-matched controls (1.36±0.39 vs 0.83±0.70 pmol/l; P<0.001). All the measured bone markers significantly differed between patients and controls (P<0.001). Spearman’s tests of correlation showed a statistically significant associa