Background: The incidence of hypocalcemia after total/completion thyroidectomy was 30 to 40% in recent studies. There is no consensus regarding the role of routine supplement of calcium and vitamin D.
Objective: To study the efficacy of routine oral calcium and vitamin D supplement to prevent postoperative hypocalcemia.
Material and Method: Sixty-eight patients who underwent total/completion thyroidectomy at the Division of Head Neck and Breast Surgery, Siriraj Hospital were included and randomized into two groups: Supplement and Control. Serum ionized calcium and total calcium were measured at 6 hour, and Days 1, 2, 3, 7 and 30 postoperatively. Clinical signs and symptoms of hypocalcemic state were recorded.
Results: The incidences of biochemical hypocalcemia were 74.3% and 96.9%, and of symptomatic hypocalcemia were 28.6% and 33.3%, in Supplement and Control groups, respectively. Most patients had hypocalcemia within the first postoperative days. Symptomatic hypocalcemia was related to ionized calcium less than 4.2 mg/dL or total calcium less than 7.9 mg/dL.
Conclusion: The incidence of post-thyroidectomy hypocalcemia was high. Most occurred within 24 hours but only 30% of these patients became symptomatic. The immediate postoperative calcium supplement may prevent this condition.

Keywords: Calcium, Hypocalcemia, Hypoparathyroidism, Thyroidectomy, Vitamin D