The postoperative levels of PTH were not significantly affected by histological diagnosis or thyroid volume, and the presence of thyroid cancer was not related to an increased risk of low PTH levels after thyroid surgery; however, patients with lymph node metastasis were at higher risk of postoperative hypoparathyroidism (5.2%, p = 0.028). The gene discussed is PTH; the disease is hypoparathyroidism.