Correlation of serum magnesium with serum levels of 25-hydroxyvitamin D in hemodialysis patients

Introduction 25-hydroxyvitamin D (25-OH vitamin D) is the main circulating metabolite of vitamin D (1). While the biological active form of vitamin D is 1,25(OH)2 vitamin D, synthesized in the kidney, it is broadly accepted that the measurement of circulating 25(OH) vitamin D offers better evidence with respect to the patients’ vitamin D status (1,2). Recently, various studies have shown the role of plasma 25(OH) vitamin D levels in mineral metabolism dysregulation in chronic renal failure. It has been found that a moderate reduction in plasma 25(OH) vitamin D levels plays a role in the development of secondary hyperparathyroidism in patients on hemodialysis, while a greater reduction in plasma 25(OH) vitamin D levels is related to osteomalacia and with the risk of emerging osteoporosis. It has been also found that, plasma 25(OH) vitamin D deficiency has been associated with adverse cardiovascular outcomes in epidemiologic studies. Magnesium is the dominant intracellular cation (1-3). Magnesium acts as a catalyst or activator for various intracellular enzymatic reactions, predominantly those which depend upon ATP, and the magnesium– ATP complex is a key intermediate substrate (4-8). Hypomagnesemia has been associated with cardiovascular risk factors and increased co-morbidity including hypertension, dyslipidemia and atherosclerosis. Various epidemiological investigations and clinical trials have detected an inverse association between blood pressure and serum magnesium (9-12). Also, hypomagnesemia aggravates both atrial and ventricular arrhythmias (912). Changes in serum magnesium may influence some clinical features of patients on hemodialysis (4-12). While, renal excretion is the main route of elimination of magnesium from the body, a positive magnesium balance would be found in patients with kidney failure. However, the magnesium balance may be normal or even decreased in hemodialysis patients. This is possibly due to decreased dietary intake associated with worsened intestinal absorption. Impaired absorption of magnesium appears to be related to deficient synthesis of the active metabolite of vitamin D by the nonfunctioning kidneys (12-17). This study, therefore aimed to find the association of serum magnesium levels, with 25-hydroxyvitamin D levels, in patients on regular hemodialysis.