Incomplete distal renal tubular acidosis in hypomagnesemia-dependent hypocalcemia.

The mechanism perpetuating hypocalcemia in the presence of hypomagnesemia is unknown. Two patients with this disorder had elevated immunoreactive serum parathyroid hormone levels and incomplete distal renal tubular acidosis. All abnormalities were corrected with magnesium replenishment. Postulated mechanisms include (1) parathyroid hormone activation in the serum or at the site of action dependent on magnesium, and (2) abnormalities in vitamin D metabolism that can be corrected by magnesium replacement.