Magnesium, Calcium and PTH Relationships in Dialysis Patients after Magnesium Repletion

Abstract

Sixteen end-stage renal disease patients who received hemodialysis for 2.9 years with no magnesium in the dialysate were evaluated for serum calcium, magnesium and parathyroid hormone (PTH) status. Eleven of these patients became hypomagnesemic with subnormal total and ultrafiltrable serum Mg concentrations (low-Mg group). The five remaining patients had consistently normal serum Mg concentrations (normal-Mg group). All had normal total and ionized serum Ca. However, the total and ionized serum Ca levels in the low-Mg group were significantly lower than those of the normal-Mg group. Within 2 weeks of Mg repletion (by dialysis against 0.25 mMof Mg), the N-terminal PTH, total and ultrafiltrable serum Mg, and the total and ionized serum Ca increased in the low-Mg group. There was a strong negative correlation between initial serum Mg and the percent change in N-terminal PTH (r = -0.833) at 2 weeks for all patients. There was also a strong positive correlation between initial ionized Ca and total serum Mg for all patients (r = 0.774). Mg repletion decreased the incidence of cramps experienced during dialysis by all patients. These data suggest that Mg-free dialysis in some patients can cause Mg depletion, which is symptomatic and which may suppress the parathyroid gland.

Reviews: Clinical Implications of Disordered Magnesium Homeostasis in Chronic Renal Failure and Dialysis

“…Kenny et al. (72) suggested that a low Mg dialysate might be expected to have a suppressive effect on parathyroid gland function; however, most studies failed to confirm this hypothesis. Several trials on the successful use of Mg salts to control hyperphosphatemia and hypeparathyroidism (73–76) support the hypothesis that hypermagnesemia may have a suppressive effect on PTH secretion in dialysis patients (77,78).…”

Magnesium in Chronic Kidney Disease: Challenges and Opportunities

“…Some studies [48,50] indicated that serum Mg level did not influence PTH in patients on regular HD. Other studies reported a highly significant inverse correlation between Mg and PTH in HD patients [46,47,49,51,52,[55][56][57]65] . Table 1 summarizes data from clinical trials addressing the effect of Mg on serum PTH level in HD patients.…”

Clinical aspects of magnesium physiology in patients on dialysis

“…In patients on HD, there is rapid equilibration between dialysate Mg and the ultrafilterable (nonprotein bound) Mg fraction in the blood; dialysate Mg is thus a major determinant of serum levels . Magnesium‐free dialysate is associated with high rates of hypomagnesemia . Hypomagnesemia can also be induced with dialysate Mg concentrations as high as 0.5 mmol/L .…”