PTH and Hypocalcemia: After incorporating these variables into multivariate analysis, it was found that non-prophylactic intravenous calcium supplementation(OR 14.360, 95% CI 3.387-60.889, P <0.001), high level of preoperative PTH (OR 1.002, 95% CI 1.000-1.003, P = 0.001) and ALP (OR 1.005, 95% CI 1.002-1.007, P <0.001), and low level of preoperative serum calcium (OR 0.000, 95% CI 0.000-0.021, P <0.001) were risk factors for postoperative severe hypocalcemia (Table 4).