Uremia and Bone metabolic disorders

The increased skeletal resistance to PTH is a common abnormality underlying behind bone and calcium metabolic disorder associated with uremia, however, its presise pathophysiology remains unknown. The shortage of 1, 25-dihydroxyvitamin D is one of the factors to increase skeletal resistance, however, it is not the only patogenesis. Disturbed interaction between PTH and osteoblasts may account for, at least in part. We measured serum levels of osteoclastogenesis inhibitory factor/osteoprotegerin (OCIF/OPG), a natural circulating decoy ligand for osteoclast differentiation factor, in 46 predialysis patients and 21 dialysis patients to elucidate its involvement in the increased skeletal resistance to PTH found in uremia. Serum OCIF levels showed a positive correlation with creatinine levels. Twenty four hours-Ccr and the reciprocal number of serum OCIF level in predialysis patients also showed a clearer positive correlation. The OCIF molecules accumulated in uremic serum preserved the binding affinity to osteoclast differentiation factor. In conclusion, OCIF is a possible candidate for an uremic toxin to cause the increased skeletal resistance to PTH. The increased skeletal resistance to PTH should be the consequence of many factors associated with uremia