Nephrol Dial Transplant (2002) 17: 6-9
© 2002 European Renal Association-European Dialysis and Transplant Association
Use and indication of vitamin D and vitamin D analogues in patients with renal bone disease
University of Kentucky Medical Center, Division of Nephrology, Bone and Mineral Metabolism, Lexington, Kentucky, USA
Abstract
Vitamin D plays a pivotal role in the pathogenesis and treatment of renal bone disease. Vitamin D levels decline in the early phase of renal failure, however, through a compensatory mechanism parathyroid hormone (PTH) stimulates the production of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3, calcitriol) to return it to normal circulating concentrations. Nevertheless, resistance to calcitriol is observed and may be related to the decreased presence of the heterodimeric, DNA-binding partner for the vitamin D receptor protein. In end-stage kidney disease (ESKD) the circulating levels of calcitriol are invariably low. The indications of vitamin D therapy are the replacement of the missing hormone vs suppression of hyperparathyroidism (HPT) requiring daily low-dose oral vs intermittent ‘pulse’ or oral administration. However, this therapy must be accompanied by careful patient monitoring to avoid hypercalcaemia and low bone turnover. Low bone turnover is not merely a histologic entity, but a clinical condition associated with a high risk of extraosseous calcifications, in particular in the cardiovascular system, leading to increased morbidity. Thus, determination of bone turnover in patients with ESKD is essential. Bone biopsy is the gold standard to assess bone turnover, however, it is not always available and nephrologists rely on PTH levels. The intact PTH assay measures PTH(1–84) and large C-PTH fragments, which may antagonize the PTH(1–84) effects on bone. An assay that measures exclusively PTH(1–84) has recently become available and a calculated PTH(1–84)/C-PTH fragment ratio has been shown to be the best predictor of bone turnover in patients with ESKD not treated with vitamin D or with other medications known to affect bone metabolism. 1,25-dihydroxy-22-oxavitamin D3 (22-oxacalcitriol, OCT) is a vitamin D analogue that could control serum PTH concentrations without deleterious effects on bone.
Keywords: bone turnover; calcitriol; OCT; parathyroid hormone; renal failure; vitamin D analogues
Notes
Correspondence and offprint requests to: H. H. Malluche, MD, University of Kentucky Medical Center, Division of Nephrology, Bone and Mineral Metabolism, Room MN566, 800 Rose Street, Lexington, KY 40536-0298, USA. Email: hhmall{at}uky.edu
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