The treatment strategy for differentiated thyroid cancer consists of a combination of surgery, iodine 131 therapy, and thyroxine suppression therapy. Among them, TSH suppression therapy is necessary after DTC surgery, and levothyroxine supplementation serves two purposes: 1) to correct the deficiency of thyroid hormones after thyroidectomy, and 2) a more important purpose, i.e., to inhibit the growth of differentiated thyroid cancer cells and reduce the recurrence rate of thyroid cancer. Because differentiated thyroid cancer cells, like normal thyroid tissue cells, have TSH receptors expressed on the cell surface. Therefore, differentiated thyroid cancer is stimulated to grow by TSH, and if TSH can be suppressed, tumor cell growth will be inhibited. TSH suppression level is strongly associated with recurrence, metastasis and cancer-related death of differentiated thyroid cancer, and this association is especially clear for those with high-risk DTC. Cancer-related death and recurrence rates were increased with TSH >2 mU/L. Postoperative TSH suppression to <0.1mU/L in patients with high-risk DTC resulted in a significant reduction in tumor recurrence and metastasis, and postoperative TSH suppression to 0.1~0.5mU/L in patients with low-risk DTC significantly improved overall prognosis, while further suppression to <0.1mU/L only increased side effects without improving prognosis. The specific recommendations of the thyroid cancer treatment guidelines for initial TSH suppression after DTC surgery are as follows: 1. For patients with high risk thyroid cancer, TSH <0.1mU/L is recommended. 2. For patients with moderate risk thyroid cancer, TSH control of 0.1-0.5mU/L is recommended. 3. For low risk patients who have received residual thyroid removal therapy and whose serum Tg is below detectable levels, TSH levels can be maintained at the lower limit of the normal reference range. Similar recommendations apply to low-risk patients who have not received residual thyroid removal therapy but whose serum Tg is below detectable levels. 4. Low-risk patients who have received residual thyroid removal therapy and have low serum Tg levels may maintain TSH levels at or slightly below the lower limit of the normal reference range and be continuously monitored for risk of recurrence. Similar recommendations apply to low-risk patients who are not treated with residual thyroid removal but have high serum Tg measurements and need to be monitored continuously. 5. Low-risk patients who have undergone unilobar thyroidectomy may have TSH levels in the low to mid normal reference range and should be monitored continuously. If the patient's TSH level can be maintained at this level, thyroid hormone therapy may also be withheld.