Disorders of Magnesium, Calcium, and Phosphorus

Magnesium plays a key role in a number of metabolic processes such as energy production, storage, and utilization in the form of adenosine triphosphate and in some enzymatic reactions involved in protein synthesis mechanisms.

Abstract

Magnesium is the fourth most abundant cation in the human body, behind sodium, potassium, and calcium, and the second most common cation in the intracellular fluid (1,2). The normal human body contains 21 to 28 grams of magnesium (3); approximately 53% in the bone, 27% in the muscles, 19% in the nonmuscular soft tissues, and only 1% in the extracellular fluid (4). Normal serum concentrations range from 1.6 to 2.6 mg/dl. Magnesium has been shown to be an essential component in more than 300 critical enzymatic reactions (5). Magnesium plays a key role in a number of metabolic processes such as energy production, storage, and utilization in the form of adenosine triphosphate (ATP) and in some enzymatic reactions involved in protein synthesis mechanisms. Magnesium also plays important roles in the control of neuronal activity, neuromuscular transmission, cardiac excitability, and cardiovascular tone (6). The kidney is the principal organ involved in magnesium regulation (7). During magnesium deprivation, the kidney conserves magnesium. However, if excess magnesium is taken, it is rapidly excreted in the urine. Phosphate depletion is commonly associated with renal magnesium wasting and hypomagnesemia. The administration of phosphate corrects the abnormality. Magnesium is needed to maintain normal potassium and calcium metabolism; hypomagnesemia results in renal potassium wasting and impairment of the secretion of parathyroid hormone (PTH) (8–10) (Figure 1).