Effect of hypermagnesemia on circulating plasma parathyroid hormone in patients on regular hemodialysis therapy.

This study was designed to assess the influence of magnesium on circulating plasma immunoreactive parathyroid hormone (iPTH) in end-stage renal disease. 20 patients receiving regular hemodialysis therapy underwent plasma measurements of iPTH and 25-hydroxycholecalciferol (25-OHCC) concentrations before and 10 weeks after the magnesium concentration in the dialysate was increased from 0.75 to 1.50 mmol/l. This resulted in a 36% rise in the mean predialysis plasma magnesium concentration from 1.25 to 1.70 mmol/l (p less than 0.001) and a 23% fall in the mean plasma iPTH concentration from 546 to 418 ng/l (p less than 0.001). Mean plasma concentrations for calcium, phosphate, and 25-OHCC also decreased, but these changes were not significant. In conclusion, we have demonstrated that a rise in plasma magnesium concentration from elevated to significantly higher levels reduces circulating plasma iPTH in normocalcemic uremic patients with initially both normal and raised plasma PTH levels.