Preoperative Vitamin D Deficiency as a Predictor of Post‐total‐thyroidectomy Hypocalcemia

Objectives: Understand the relationship between preoperative vitamin D deficiency and post‐total‐thyroidectomy hypocalcemia. Methods: Retrospective study examining 264 total and completion thyroidectomies between 2007‐2011. Included patients had a recorded 25OH‐D level within 21 days prior to or 1 day following surgery, were not taking ergocalciferol (D2) at the time of their lab draw, did not have a primary parathyroid gland disorder, and were not taking calcitriol (1,25 dihydroxy‐D3) prior to surgery. Some patients were repleted preoperatively if a low 25OH‐D level was identified. Preoperative 25OH‐D, concurrent neck dissection, integrity of parathyroid glands, final pathology, postoperative parathyroid hormone (PTH), calcium nadir and repletion, and length of stay were examined. Results: In this cohort, a mean of 3 parathyroid glands were identified during surgery. Multinodular goiter and papillary thyroid carcinoma were the most common pathologies. Hypocalcemia, defined as a corrected calcium <8.4 mg/dL, and drain placement were the most common reasons for length of stay >1 night. The average preoperative 25OH‐D for all patients was 24.98 ng/mL and the overall rate of hypocalcemia was 37.5%. Low preoperative 25OH‐D did not predict postoperative hypocalcemia ( P = 0.96), however, it did predict the need for postoperative calcitriol administration (p=0.01). Lower postoperative PTH levels ( P = 0.001) predicted postoperative hypocalcemia. Conclusions. Lower postoperative PTH predicts post total thyroidectomy hypocalcemia. Preoperative 25OH‐D did not predict hypocalcemia as has been previously described although it did predict the use of calcitriol postoperatively. We recommend that 25OH‐D be assessed and, if indicated, repleted preoperatively in patients undergoing total thyroidectomy.