Current concepts of parathyroid hormone and vitamin D metabolism: perturbations in chronic renal disease

Renal osteodystrophy is a serious complication of uremia, characterized pathologically by several alterations in bone structure. Osteitis fibrosa cystica is often present, representing the abnormal bone resorptive effects of secondary hyperparathyroidism; osteomalacia is also present, representing defective mineralization of osteoid matrix. Less commonly, osteosclerosis and osteoporosis are also seen. These pathological processes are the consequence of abnormalities in the metabolism of calcium, phosphorus and collagen, some of which, in turn, are secondary to perturbations in parathyroid hormone and vitamin D metabolism. The major aspects of parathyoid hormone and vitamin D metabolism and the effects of chronic renal disease on the metabolism of these hormones, serve as the subject for this review.