PTH and Hypocalcemia: Because 25-OHD level plays an essential role in both Ca and PTH regulation, it has been hypothesized that perhaps preoperative 25-OHD level could be a significant factor affecting the risk of hypocalcemia and altering the accuracy of qPTH in predicting hypocalcemia after total thyroidectomy.[16] Our study aimed at addressing these two related issues by evaluating whether preoperative 25-OHD was a significant factor in postthyroidectomy hypocalcemia and examining whether preoperative 25-OHD level affected the accuracy of single qPTH in predicting hypocalcemia.