On the Effect of Magnesium on the PTH Secretion in Uremic Patients on Maintenance Hemodialysis

Abstract

The Mg, Ca and immunoreactive parathyroid hormone (PTH) serum levels were determined in 22 uremic patients on chronic hemodialysis with different Mg concentrations in the dialysate. Baseline levels of PTH, Ca and Mg were obtained over a 4-month-period whilst on Mg dialysis of 1.5 mEq/l. Patients were then divided into three groups: 10 patients were dialyzed for 6 months with 0.5 mEq/l of Mg, 7 patients with 1.5 mEq/l, and 5 patients with 2.5 mEq/l Mg. At the end of the 6-month period with differentiated Mg dialysis the three groups were characterized by significantly different Mg serum levels. On the contrary, no significant changes were observed in the PTH or the Ca serum levels. The results of this study indicate that PTH secretion in uremic patients on regular hemodialysis is not appreciably influenced by the Mg serum levels.

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

“…Increased dialy sate Mg during hemodialysis therapy was reported to decrease serum PTH activity in one study [1], but other authors failed to observe any reduction [12]. Similarly, Kaye [3] did not notice any reduction in the weight of the parathyroid gland after 4 weeks of increased Mg intake in uremic rats.…”

Plasma and Tissue Levels of Magnesium in Chronically Hemodialyzed Patients: Effects of Dialysate Magnesium Levels

“…On the other hand, further investi gations have shown that low sMg suppresses the PTH secre tion both in vitro [17] and in vivo [18][19][20][21][22]. In our patients undergoing chronic hemodialysis with various dMgs (0.25, 0.75, 1.25 mmol/1) the sMg paralleled the dMg changes, and, though the changes of the sMg were statistically significant and maintained for a long time, they were not associated with any significant change in the serum iPTH levels [10,11], A certain relationship between Mg depletion and hypo calcemia has been reported and attributed to multiple fac tors [1,[18][19][20][21][23][24][25][26]. In our patients on low dMg (0.25 mmol/1) the values of the sCa, measured before and after dialysis, were not significantly different from the corre sponding values obtained in the patients on standard dMg (0.75 mmol/1), when in both cases the dialysate Ca concen tration was kept at 1.75 mmol/1 [unpublished observations].…”

“…The excess bMg has been postulated to have an important role in the bone minerali zation defect and, in general, in the pathogenesis of renal osteodytrophy [54,56], Our investigations [10,11] have shown that the reduction of dMg is followed by a significant fall of bMg; this has been found to be associated with an improvment of the histological bone appearances concern ing osteoporosis and, in part, osteomalacia [unpublished observations]; however, not significant changes were ob served in the severity of osteitis fibrosa. This is not surpris ing if we consider that this type of lesion is due to an in creased osteoclastic activity caused by secondary hyper parathyroidism, which is not appreciably affected by the sMg [10,11], Catto et al…”

“…In the uremics of our unit dialyzed with a standard dMg of 0.75 mmol/1 and receiving no Mg-containing drugs, the mean value of sMg was 1.3 ± 0.21 mmol/1, ranging from 0.95 to 1.75 mmol/1 [12,13]. Our previous investigations showed that in chronically dialyzed patients a dMg of 0.25 mmol/1 produces a significant decrease in the sMg as early as 1 month after the beginning of dialysis performed with low dMg [10,11]. In the uremics kept on 0.25 mmol/1 in the dialysate for a prolonged period, the sMg is within normal limits both at the end of each hemodialysis and for 24 h afterwards, remaining slightly higher than normal fora few hours only before the next dialysis [unpublished observa tions].…”

Serum magnesium in association with parathyroid hormone levels in routine hemodialysis patients

“…Hyperphosphatemia, hypermagnesemia and hypocalcemia are detectable in advanced chronic kidney disease. Disturbances in Mg metabolism in chronic renal failure may partly contribute to the development of chronic kidney disease-mineral bone disorder (5,6). It has been supposed that plasma Mg has a principal role to regulate the secretion of PTH.…”