PTH and Hypocalcemia: This article reviews the relationship between postoperative hypocalcemia and its suspected risk factors, including age, sex, serum magnesium, vitamin D, high-risk pathological subtype, parathyroid injury, and parathyroid hormone levels, and assesses the ability of preoperative and postoperative parathyroid hormone levels and changes therein at various time points to predict postoperative hypocalcemia.