Follow-up of long-term treatment of predialysis renal bone disease with 1-alpha-hydroxy-derivatives of vitamin D.

Patients with predialysis chronic renal failure and bone disease were treated with 1 alpha-hydroxy-derivatives of vitamin D. The observation period consisted of 22 patient years. All patients showed histological improvement of renal osteodystrophy after the initial 6 months of treatment. Bone resorption indices improved most strongly. There was also a considerable decrease of non-mineralized osteoid and no change in the total trabecular bone volume. Hypercalcemia occurred 24 times in 9 patients. Although in general the 1,25-(OH)2-vitamin D serum levels were increased at the time of hypercalcemia, as compared to the preceding non-hypercalcemic period, no elevation above the normal range occurred. In cases of hypercalcemia two different groups of patients, with suppressed and non-suppressed levels of iPTH respectively, could be distinguished. In both groups different significant correlations between serum 1,25-(OH)2-vitamin D and serum calcium levels were found. If serum iPTH was not suppressed hypercalcemia was more severe. It is concluded that the occurrence and severity of hypercalcemia in patients with chronic renal failure during treatment with 1 alpha-hydroxy-derivatives of vitamin D is related to the presence of parathyroid hormone.