Effect of magnesium on phosphorus and calcium metabolism.

Magnesium is an element that occurs ubiquitously in nature. Magnesium and calcium metabolism are closely related. The intestinal absorption and the renal excretion of the two ions are interdependent. The relationship between phosphorus and magnesium metabolism is more difficult to demonstrate. The most frequent causes of hypomagnesemia in children are reduced intake, impaired intestinal absorption, renal loss and genetic diseases. Hypomagnesemia is reflected clinically in the nervous system, and there are neurophysiological and metabolic changes. Severe hypomagnesemia induces secondary hypocalcemia in most experimental animals except rats. Furthermore, severe hypomagnesemia induces functional hypoparathyroidism. In vitro studies have demonstrated that magnesium can modulate parathyroid hormone (PTH) secretion in a similar way to calcium. An acute decrease in magnesium concentration stimulates PTH secretion, and an acute increase in concentration decreases secretion. Magnesium is likely to play an important role in vitamin D metabolism. Some patients with hypocalcemia and magnesium deficiency are resistant to pharmacological doses of vitamin D or may have a form of magnesium-dependent vitamin D-resistant rickets. Phosphate depletion has been observed to be accompanied by an increase in urinary magnesium and calcium. In pediatrics the syndrome of phosphate depletion is observed particularly often in premature babies, who often receive a low-P diet. Magnesium is involved in many of the biochemical reactions that take place in the cell, and particularly in processes involving the formation and utilization of ATP. Thus, at the cellular level, magnesium plays a key role in ionic transport processes.