Effects of pamidronate and calcitriol on the set point of the parathyroid gland in postmenopausal hemodialysis patients with secondary hyperparathyroidism

Background/Aims: Secondary hyperparathyroidism may worsen after the administration of pamidronate in postmenopausal hemodialysis (HD) patients. The aim of this study was to evaluate the short-term effect of coadministration of calcitriol and pamidronate on dynamic parathyroid hormone (PTH) secretion. Methods: Fifteen postmenopausal women undergoing regular HD with serum intact PTH levels of >200 pg/ml were enrolled. The PTH-ionized calcium (iCa) curve was evaluated by the response to hypo- and hypercalcemia induced with 1 and 4 mEq/l of dialysate calcium, respectively. Parameters were compared after pamidronate was administered and after coadministration of pamidronate and calcitriol. Changes in serum levels of maximal serum PTH (PTH_max), basal PTH (PTH_base) and minimal PTH (PTH_min) were evaluated. Results: Pamidronate therapy resulted in a decrease in predialysis basal plasma iCa (p <0.05) and an increase in PTH_max (p <0.01), PTH_base (p <0.01) and PTH_min (p <0.01). The change in serum iCa and PTH was reversed after the coadministration of calcitriol and pamidronate. Conclusion: Our study demonstrated that pamidronate therapy is associated with a reduced plasma iCa and increased PTH secretion. These adverse effects may be reversed by calcitriol. These findings suggest that in considering pamidronate treatment in postmenopausal patients with osteoporosis receiving HD, it might be safer to add calcitriol to prevent the increased PTH secretion.