Persistent hypomagnesaemia following parathyroid surgery, hypermagnesuria as a possible cause.

A patient who had prolonged hyperparathyroidism with extensive bone involvement developed delayed post-surgical complications of pseudogout and the hungry bone syndrome with persistent hypocalcaemia and hypomagnesaemia. Although urinary calcium excretion was appropriate for the hypocalcaemia, there was severe excessive renal loss of magnesium despite the hypomagnesaemia. Renal magnesium excretion returned to normal only after correction of the hypocalcaemia. Hypermagnesuria may be an important cause of resistant hypomagnesaemia after parathyroid surgery.