PTH and vitamin D deficiency: We iteratively removed from the regression all parameters with statistically non-significant p values (sex, p = 0.238; age, p = 0.418; preoperative TSH, p = 0.425; preoperative calcium, p = 0.471; and EGFR, p = 0.798), building a regression model including only preoperative PTH (p = 0.029, odd ratio 1.012) and vitamin D level (p = 0.029, odd ratio 0.703 for vitamin D insufficiency).