Thyroxine tablets are taken after thyroidectomy. In clinical practice, thyroidectomy is performed for benign thyroid diseases and malignant thyroid diseases. In benign thyroid diseases such as nodular goiter, thyroid adenoma, and cystic thyroid adenoma, unilateral thyroidectomy is not associated with a decrease in thyroxine levels, and no supplemental medication is required. For malignant thyroid tumors, that is, thyroid cancer, radical resection of thyroid cancer requires total excision of the affected side plus total excision of the isthmus, plus subtotal excision of the contralateral side. After surgery, T3, T4, and free T3 and T4 will be reduced. It is necessary to supplement thyroxine tablets in appropriate amounts according to their reduced levels to avoid hypothyroidism symptoms such as weakness and mucinous edema due to reduced thyroxine levels.