Comparative effect of oral or intravenous calcitriol on secondary hyperparathyroidism in chronic hemodialysis patients.

The suppressive effects of intravenous (IVC) and oral (ORC) 1,25(OH)2D3 (calcitriol) therapies on parathyroid hormone (PTH) secretion were compared in 10 hemodialysis (HD) patients with secondary hyperparathyroidism (SHPT). These patients were randomized to receive either IVC or ORC therapy for 12 weeks, both followed by a 12-week washout period. After the washout, the patients who received IVC then switched to ORC therapy for another 12 weeks, and the patients who received ORC switched to IVC therapy. The mean dose of IVC was 2.45 +/- 0.30 micrograms/dialysis session (approximately equal to 1.05 micrograms/day) and that of ORC was 0.69 +/- 0.07 micrograms/day. A significant reduction in serum levels of intact PTH was observed after 8 weeks and that of C-PTH after 10 weeks of ORC therapy, but both fell after 6 weeks of IVC treatment. There was a concomitant reduction in serum alkaline phosphatase (AP), but it became significant 4 weeks later than in intact PTH. The maximal reductions of serum levels of intact PTH, C-PTH and AP were 74.28, 64.91, 41.97%, respectively, after IVC, and 31.57, 24.39, 22.50%, respectively, after ORC therapy. Serum calcium rose faster during ORC treatment. There were no significant changes in serum levels of phosphorus, magnesium, and albumin throughout the treatment period. We conclude that both IVC or ORC treatments result in a significant decrement in blood levels of PTH in chronic HD patients with SHPT. However, this PTH-suppressive effect is more pronounced with IVC therapy, and cannot be totally explained by either the higher dose or elevated serum calcium.