Evaluation and treatment of postthyroidectomy hypocalcemia

Transient hypocalcemia is reported to occur postoperatively in approximately 7-25% of thyroidectomy patients. Permanent hypocalcemia is seen much less frequently. Although parathyroid insufficiency is most frequently implicated in post-thyroidectomy hypocalcemia, it appears to be a phenomenon of multifactorial etiology. Preoperative hyperthyroidism causing par thyroid suppression and/or thyrotoxic osteodystrophy should also be considered as causes. Factors that increase the chance of extensive dissection such as presence of a large/substernal goiter, thyroid malignancy, or repeat operation increase the likelihood of parathyroid injury and subsequent hypocalcemia. However, an uncomplicated hemithyroidectomy does not exclude the possibility of postoperative hypocalcemia. In the present review, we provide a series of recommendations for the evaluation and treatment of this complex disorder. In brief, our suggestions are: 1) obtain a serum magnesium, phosphorus, and ionized calcium level preoperatively and again at 12 and 24 hours after the procedure, 2) treat a postoperative serum ionized calcium of less than of 1.12 mMol/L in the asymptomatic patient with oral calcium and vitamin D preparations, 3) treat symptomatic hypocalcemia and/or a serum ionized calcium of less than 1.0 mMol/L with intravenous calcium. Calculations to adjust or correct serum calcium for serum albumin tend to overestimate the true serum calcium and are not recommended.