Relationship between serum magnesium and parathyroid hormone levels in hemodialysis patients

Acute magnesium (Mg) infusion decreases patathyroid hormone (PTH) secretion . However, the effect of chronic hypermagnesemia on PTH levels in dialysis patients is not well established. We studied 110 hemodialysis patients (mea n age, 55 +/- 14 years; time on dialysis, 35 +/- 28 months) not receiving v itamin D and undergoing dialysis with an Mg dialysate concentration of 1.2 mg/dL. The primary phosphate binder was calcium carbonate, and 43% of the p atients also needed aluminum hydroxide. During a 6-month period, calcium (C a), phosphorus (P), and total serum Mg were measured every 2 months; intact PTH and aluminum (Al) were measured every 6 months. The mean value of each parameter was computed. Hypermagnesemia (serum Mg > 2.47 mg/dL) was observ ed in 73% of the patients. Mg and Ca were inversely correlated with PTH lev els (r = -0.48; P < 0.001 and r = -0.21; P < 0.05, respectively). After adj usting for Ca and P (partial correlation analysis), Mg and PTH were inverse ly correlated (r = -0.58; P < 0.001). A stepwise multiple regression analys is showed that PTH levels were predicted by Mg (P < 0.001), alkaline phosph atase (P < 0.01), and P levels (P < 0.05; multiple R = 0.57; P < 0.001), wh ereas Ca level, sex (dummy variable), diabetes (dummy variable), time on di alysis, and Al level were not predictive. Patients with inadequately low PT H levels (relative hypoparathyroidism, PTH < 120 pg/mL; n = 52) showed grea ter serum Mg concentrations than the rest(n = 58; 3.01 +/- 0.33 v 2.63 +/- 0.38 mg/dL; P < 0.001). In conclusion, serum Mg concentrations in dialysis patients are independently associated with PTH levels, suggesting that chro nic hypermagnesemia may decrease PTH secretion and/or synthesis. In additio n, chronic hypermagnesemia of dialysis patients may have a role in the path ogenesis of adynamic bone disease. (C) 1999 by the National Kidney Foundati on, Inc.