The action of 1,25 (OH)2D3 on turnover kinetic, remodelling surfaces and structure of trabecular bone in chronic renal failure.

Fibroosteoclasia as well as osteoidosis are reduced by 1,25(OH)2D3 treatment if secondary hyperparathyroidism preexists. Fibrosteoclasia completely disappeared after 6 months therapy in some cases. 1,25(OH)2D3 has no or only a very slight effect on the disturbed mineralization in type II of renal bone disorder (osteoidosis only, no signs of secondary hyperparathyroidism). The appositional rate of the osteoblasts increases under 1,25(OH)2D3 treatment if serum PTH values are raised. 1,25(OH)2D3 seemed to have, in the chosen dosage of this study, a self-limiting effect by reducing the bone-forming cells, i.e. the osteoblasts. This state already represents an overtreatment of the underlying bone disease.