Hypomagnesemia associated with hypocalcemia after total thyroidectomy: an observational study.

INTRODUCTION: Serum magnesium is frequently low in patients with hypocalcemia after total thyroidectomy. The aim of the present study was to analyze the variations in serum magnesium and calcium concentrations after total thyroidectomy, and the relationship between both ions. MATERIALS AND METHODS: We conducted an observational study of 142 patients who had undergone total thyroidectomy, measuring serum calcium and magnesium levels preoperatively and on the day following surgery. The incidence of postoperative hypocalcemia was compared with that of postoperative hypomagnesemia. RESULTS: A total of 142, total thyroidectomies were performed: 54 patients (38%) presented with hypocalcemia on the first postoperative day. A marked decrease in blood magnesium in the group of patients with hypocalcemia was observed when compared to those with normal calcemia on the first postoperative day (mean variation respectively, 0.125 ± 0.065 mmol/L versus 0.035 ± 0.020 mmol/L; P = 0.0002). CONCLUSION: Hypomagnesemia is significantly associated with early hypocalcemia following thyroidectomy.