Morphological effects of vitamin D and its analogs on bone.

Recent studies employing analogs of vitamin D in the treatment of clinical and experimental renal osteodystrophy indicate remarkable healing of morphological and biochemical skeletal lesions. After short periods of therapy, 25-hydroxycholecalciferol or 1,25-dihydroxycholecalciferol normalizes most of the histological abnormalities of the human uremic skeleton and significantly suppresses elevated levels of circulating immunoreactive parathyroid hormone. 25-Hydroxycholecalciferol appears to stimulate individual osteoblastic activity but does not increase the number of bone forming cells. Accumulated evidence suggests a direct effect of vitamin D and its metabolites on uremic bone.