Impact of postoperative magnesium levels on early hypocalcemia and permanent hypoparathyroidism after thyroidectomy.

Background: Postoperative hypocalcemia is a common complication of thyroidectomy. Magnesium is known to modulate serum calcium levels and hypomagnesemia may impede correction of hypocalcemia. The purpose of this study was to investigate whether hypomagnesemia after thyroidectomy has any impact on early hypocalcemia and/or permanent hypoparathyroidism.

Methods: We conducted a retrospective review of prospectively maintained databases. Inclusion criteria were total or completion total thyroidectomy with postoperative magnesium levels available. The incidence of postoperative hypocalcemia was correlated with postoperative hypomagnesemia and other risk factors.

Results: Two hundred one cases were included. Twenty-six patients (13%) developed postoperative hypomagnesemia. Hypomagnesemia (p = .002), cancer diagnosis (p = .01), central neck dissection (p = .02), and inadvertent parathyroid resection (p = .02) were significantly associated with hypocalcemia. On multivariate analysis, only hypomagnesemia (p = .005) remained significant. Hypomagnesemia was also a significant predictor of permanent hypoparathyroidism (p = .0004).

Conclusions: Hypomagnesemia is significantly associated with early hypocalcemia and permanent hypoparathyroidism after thyroidectomy. Magnesium levels should be closely monitored in patients with postthyroidectomy hypocalcemia.