Effects of lowering dialysate calcium concentration on mineral metabolism and parathyroid hormone secretion: a multicentric study.

This prospective study was conducted with the aim of examining the efficacy of lowering dialysate calcium (dCa) in order to: (i) stimulate bone turnover in hemodialysis patients with biochemical signs of adynamic bone disease (ABD) (hypercalcemia, normal alkaline phosphatase and intact parathyroid hormone (iPTH) <150 pg/mL); and (ii) diminish hypercalcemia in patients with secondary hyperparathyroidism (sHPT) (hypercalcemia, high alkaline phosphatase and iPTH > 400 pg/mL), thus permitting the use of calcium-containing phosphorus binders and vitamin D metabolites. Patients were divided into: an ABD-treated group (24 patients), a sHPT-treated group (18 patients), an ABD-control group (12 patients) and a sHPT-control group (11 patients). For the ABD- and sHPT-treated patients, hemodialysis was conducted with dCa 1.5 mmol/L for three months and then with dCa 1.25 mmol/L for an additional three months, while in the control groups hemodialysis was conducted with dCa 1.75 mmol/L during the entire study. Reduction of dCa in patients with ABD caused a slight but insignificant decrease of Ca, but a significant and permanent increase of bone-specific alkaline phosphatase and intact parathyroid hormone level serum levels. Reduction of dCa in patients with sHPT slightly but insignificantly decreased Ca and intact parathyroid hormone level values. Nevertheless, this enabled the calcium-based phosphate binder dose to be raised and vitamin D3 metabolites to be introduced. Logistic regression analysis indicated that milder bone disease (both ABD and sHPT) was associated with more the favorable effect of dCa reduction. Thus, low dCa stimulated parathyroid glands and increased bone turnover in ABD patients, and enabled better control of mineral metabolism in sHPT patients.