OBJECTIVE: For the normalization of serum magnesium (Mg) concentration, dialysate Mg concentration tends to be reduced in continuous ambulatory peritoneal dialysis (CAPD) patients. The aim of this study was to evaluate the influence of Mg on parathyroid hormone (PTH). DESIGN: Prospective study of the utilization of Mg-free dialysate for 8 weeks. SETTING: Dialysis service, Itabashi Hospital, Nihon University School of Medicine. PATIENTS: Five stable CAPD patients (1 male; 4 female; age 49.7 +/- 1.3 years; duration of CAPD 27 +/- 9 months). MAIN OUTCOME MEASURES: Serum Mg, serum high sensitive PTH, and Mg content in mononuclear cells were measured at 4-week intervals. RESULTS: In comparison to baseline, serum Mg concentration was significantly reduced at week 4 (p < 0.01) and week 8 (p < 0.01), and serum PTH was significantly increased at week 4 (p < 0.05) and at week 8 (p < 0.05). However, the PTH level at week 8 was lower than that at week 4. Furthermore, the Mg content in mononuclear cells was significantly decreased at week 4 (p < 0.01) and at week 8 (p < 0.01). Serum-ionized calcium and phosphate concentrations did not change. CONCLUSIONS: The removal of Mg by Mg-free dialysate leads to Mg depletion in CAPD patients. In addition, Mg depletion stimulates PTH synthesis or secretion at 4 weeks, but at 8 weeks PTH synthesis or secretion is also influenced by other factors.

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