Thyroid cancer can be divided into differentiated and undifferentiated types according to histology. Differentiated thyroid cancer can be divided into papillary thyroid cancer and follicular thyroid cancer. Papillary thyroid cancer accounts for 75% of all thyroid cancers, while the latter accounts for 16%. Papillary thyroid cancer is the most widespread, while follicular thyroid cancer is most commonly seen after the age of 20. Thyroid cancer accounts for about 1% of all cancers. According to the statistics of International Cancer Society, the incidence of thyroid cancer is increasing year by year in various countries. According to epidemiological studies, the incidence of thyroid cancer in China is also increasing year by year, according to statistics, thyroid cancer accounts for 10% of all thyroid tumors, and thyroid cancer is more common in women, with a male to female ratio of 1:2.6. Unlike other cancers that occur in the elderly, thyroid cancer occurs more often in young adults, with an average age of onset of about 40 years. Its treatment is mainly surgical. There are still controversies regarding the appropriate scope of surgical resection of the primary lesion of differentiated thyroid cancer, the indications and scope of cervical lymph node dissection, the role of postoperative thyroid residual radioactive iodine removal and thyroxine suppression therapy. Adjuvant therapy after surgery for patients with differentiated thyroid cancer (DTC) includes 131I removal of residual thyroid tissue and TSH (thyroid stimulating hormone) suppressive therapy (i.e. supraphysiologic dose thyroid hormone therapy). Thyroid hormone therapy has important roles: 1. DTC requires supplemental exogenous thyroxine after surgery and iodine-131 has removed all of the thyroid gland to correct the condition of hypothyroidism (low thyroid) caused by insufficient thyroid hormones in the body, maintain the normal metabolism of the body, and reduce the complications of low thyroid. 2. TSH can stimulate the growth of residual thyroid cancer. Using thyroid hormone feedback to inhibit TSH secretion by pituitary gland and keep serum TSH at a low level can reduce the stimulation of TSH on thyroid tissue and its recurrent metastases, reduce DTC recurrence and metastases, and prolong survival. 3. Elevated thyroglobulin (Tg) during TSH suppression therapy suggests DTC recurrence or metastasis, suggesting that such patients need to discontinue thyroxine preparations for further review.