PTH and Hypocalcemia: Four factors were found to be significantly associated with postoperative hypocalcemia: Lymph node metastasis (P = 0.049, OR = 2.6), total thyroidectomy (P = 0.001, OR = 8.0), 25(OH)D3 level (P = 0.0005), and PTH level (P < 0.001, OR = 12.6).