Vitamin D therapy in patients receiving dialysis.

Secondary hyperparathyroidism is found in a large proportion, but not all patients on dialysis. Calcitriol controls moderate hyperparathyroidism in most patients but only in a proportion of those with advanced hyperparathyroidism. Patients with nodular parathyroid hyperplasia respond less frequently, presumably because of monoclonal growth and diminished calcitriol-receptor expression by parathyroid cells. In patients with nodular parathyroid hyperplasia, parathyroidectomy is an important alternative to calcitriol treatment. A priori reasoning indicates that prophylactic administration of calcitriol (to prevent parathyroid hyperplasia) is a reasonable option, but currently no controlled evidence for long-term efficacy of this approach without side effects is available. Intermittent administration of calcitriol by intravenous or oral routes is effective and, at least in experimental studies, superior to continuous calcitriol. However, in clinical comparisons, no superiority of intravenous versus oral or daily versus intermittent calcitriol has been documented. Calcitriol treatment must be closely supervised to prevent hypercalcemia, hyperphosphatemia, and excessive suppression of parathyroid hormone. Because of an altered dose response relationship, parathyroid hormone levels should not be completely normalized so as to prevent low bone turnover (adynamic bone lesion).