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

Abstract

Magnesium (Mg) is the fourth most abundant cation in the body, mainly located within bone and skeletal muscle. The normal total plasma Mg concentration varies in a narrow range, with approximately 60% present as free Mg ions, the biologically active form. The kidney plays a principal role in Mg balance. Approximately 70-80% of plasma Mg is ultrafilterable, and under normal circumstances, 95% of the filtered load of Mg is reabsorbed. As chronic renal failure (CRF) progresses, urinary Mg excretion may be insufficient to balance intestinal Mg absorption and dietary Mg intake becomes a major determinant of serum and total body Mg levels. Until severe reductions in glomerular filtration rate (<30 ml/min), serum Mg levels are usually normal; with lower rates of renal function, serum Mg is increased. Concerning dialysis patients, dialysate Mg plays a critical role in maintaining Mg homeostasis, with serum Mg being largely dependent on the concentration of the ion in the dialysis solution. Magnesium has been implicated in diverse consequences, both beneficial and deleterious, in patients with CRF and dialysis. Potential harmful effects of elevated Mg include altered nerve conduction velocity, increased pruritus, and alterations to osseous metabolism and parathyroid gland function (mineralization defects, contribution to osteomalacic renal osteodystrophy, and adynamic bone disease). Hypermagnesemia also may retard vascular calcification. Low Mg levels have been associated with impairment of myocardial contractility, intradialytic hemodynamic instability, and hypotension. In addition, low Mg has been also linked to carotid intima-media thickness, a marker of atherosclerotic vascular disease and a predictor of vascular events.

Evaluation of Peripheral Vascular Calcification and Serum Magnesium Level in a Group of Egyptian Hemodialysis Patients

“…Both hyper-and hypomagnesemia have deleterious consequences in CRF patients. Elevated Mg levels are associated with pruritus, and have potentially harmful effects on nerve conduction velocity, osseous metabolism and parathyroid gland function [11]. Various studies found a significant inverse correlation between serum Mg and intact parathyroid hormone (iPTH) levels [10].…”

“…Undue suppression of iPTH would result in mineralization defects and adynamic bone disease. Low Mg levels have been associated with impairment of myocardial contractility, intra-dialytic hemodynamic instability, and hypotension [11]. There is also evidence suggesting a significant role for hypomagnesemia in the pathogenesis of cardiovascular diseases in HD patients [12].…”

Vascular Smooth Muscle Cell Differentiation to an Osteogenic Phenotype Involves TRPM7 Modulation by Magnesium

“…44 Clinical studies have also shown protective anticalcification actions of magnesium. 45 In chronic dialysis patients, magnesium carbonate/calcium carbonate, used as a phosphate binder for 18 months, demonstrated a small change in calcium index. 46 Such observations have prompted an interest in using magnesium salts as phosphate binders, not only to treat hyperphosphatemia but also to inhibit development or progression of vascular calcification.…”

Magnesium Content in Daily Food Portions and the Influence of Supplementation

“…A high supply of dietary magnesium in addition to the additional intake through widely advertised and available supplements may constitute a risk of hypermagnesemia. The excessive intake of oral antacids, laxative and cathartics containing magnesium salts or swallowing of sea water may lead to hypermagnesemia (8)(9)(10).…”

“…Concentrated sources of magnesium include antacids, enemas and total parenteral nutrition (5,6). Consequently, the excessive use of preparations containing magnesium salts for medicinal purposes may constitute a health threat (7)(8)(9).…”