It is now recognized that magnesium plays an important role in calcium homeostasis. Although the effects of hypomagnesemia have been frequently reported, little has been written to suggest a clinically important role for hypermagnesemia. A case is reported in which severe hypocalcemia, with a low plasma parathyroid hormone (PTH) concentration, resulted from the therapeutic use of magnesium sulfate for toxemia of pregnancy. Following recovery, the parathyroid glands were shown to respond normally to a phosphate load. It is suggested that the hypermagnesemia directly suppressed PTH secretion, resulting in symptomatic hypocalcemia.
(Arch Intern Med 136:688-691, 1976)
Eisenbud E, LoBue CC. Hypocalcemia After Therapeutic Use of Magnesium Sulfate. Arch Intern Med. 1976;136(6):688-691. doi:10.1001/archinte.1976.03630060040009