Influence of serum magnesium on markers of calcium-phosphorus metabolism in patients on regular haemodialysis

Abstract

Secondary hyperparathyroidism is manifested early in the course of chronic kidney disease (CKD). Numerous studies have shown that serum magnesium significantly influences the function of the parathyroid glands. Serum levels of Mg in patients on regular hemodialysis were analyzed to establish their correlation with the levels of Ca, PO 4 , Alkaline phosphatase (ALP) and intact parathyroid hormone (iPTH). A total of 72 test subjects (45 men and 27 women) were divided in two groups: 60 patients with diabetes mellitus and 12 patients without diabetes. Serum Mg levels were recorded immediately before and after intermediate weekly dialysis, using low-flux dialyzers with polysulfone membranes. Student`s ttest and linear regression analysis were used to analyze the available data. In both patient groups a significant disparity (p <0.005) was registered, confirming a positive correlation between serum Mg and serum total Ca, PO 4 , ALP and urea reduction ratio (URR%), much more pronounced with diabetic patients. A strong negative correlation between serum Mg and iPTH was observed. In patients with diabetes mellitus the average iPTH was 93,5 ± 33.12 pg/mL, 41,6% of which have hypermagnesaemia in addition. In non-diabetics the average iPTH was 433.52 ± 94.89 pg /mL; hypermagnesemia was detected in 21,6% of the patients. Higher, compared to the normal levels, of serum magnesium was observed in almost twice as many diabetic patients on hemodialysis in comparison to reference values for iPTH patients on dialysis with stage 5 CKD, according to USA National Kidney Foundation's Kidney Disease Outcomes Quality Initiative (KDOQI). There is a discretely negative correlation between serum magnesium and iPTH, indicative of a suppressive effect of hypermagnesaemia on the synthesis and/or secretion of the parathyroid hormone.