Effect of serum magnesium concentration on renal handling of phosphate in a patient with primary hypomagnesemia.

We examined a case of primary hypomagnesemia with associated hypocalcemia and hyperphosphatemia. It was found, on treatment with magnesium, that there was a significant negative correlation between the serum magnesium level and the percent tubular reabsorption of phosphate, especially when the serum magnesium concentration was above 1.0 mg/dl, in the patient. It is suggested that the serum magnesium concentration might play an important role in urinary phosphate excretion, probably in relation to the parathyroid hormone function.