Effects of magnesium supplementation on post-thyroidectomy hypocalcemia: a prospective single-center study

Severe and/or symptomatic hypocalcemia due to hypoparathyroidism is the main contraindication for discharge in patients who have undergone thyroid surgery. Hypomagnesemia may contribute to the onset of hypoparathyroidism and is frequently observed after thyroid surgery in hypocalcemic patients. The impact of prophylactic and postoperative Magnesium supplementation on postoperative hypocalcemia and hypomagnesemia was prospectively evaluated by comparing patients undergoing prophylactic supplementation to a control group of patients who had only received magnesium after evidence of postoperative hypomagnesemia.

One hundred and twenty patients who underwent a total thyroidectomy participated in the study. Seventy-three patients were included in the study group, 47 in the control group. Prior to surgery, patients in the study group were given magnesium orally for 5 days; postoperatively, calcium and magnesium was administered to all patients who displayed hypocalcemia and hypomagnesemia.

Postoperative biochemical hypocalcemia (serum calcium <8.5 mg/dL, regardless of its clinical severity) was found in 60 patients (50%) on D1 and in 58 patients (48.4%) on D2. Among hypocalcemic patients, hypomagnesemia was recorded in 29 at D1 (48%), and in 46 at D2 (79%). A significant positive correlation was found between magnesium, calcium, and parathyroid hormone in the first two postoperative days, while a significant inverse correlation occurred for these same parameters and length of hospital stay (P<0.001). One hundred and five patients (87.5%) were discharged as expected on the second postoperative day (65 in the study group, 40 in the control group, P=0.724), whereas 15 patients (12.5%) required prolonged hospitalization (eight in the study group, seven in the control group, P=0.721). The Study group only showed significantly higher magnesium levels on the first postoperative day (P=0.03).

Although magnesium and calcium levels showed the same trend after thyroidectomy, neither Magnesium prophylaxis nor Magnesium treatment influenced the clinical course of postoperative hypocalcemia.