Although most DTC patients have a good prognosis and low mortality rate, about 30% of DTC patients will develop recurrence or metastasis, 2/3 of which occur within 10 years after surgery, and those with postoperative recurrence and distant metastasis have a poor prognosis. The purpose of long-term follow-up for DTC patients is to: ① monitor those who are clinically cured for early detection of recurrent tumors and metastases; ② dynamically observe the progress of disease and treatment effect for those who have recurrence or survive with tumors, and adjust the treatment plan; ③ monitor the effect of TSH suppression therapy; ④ dynamically observe the disease of certain concomitant diseases (such as heart disease, other malignant tumors, etc.) of DTC patients. (iv) dynamic observation of certain concomitant diseases (such as heart disease, other malignant tumors, etc.) in DTC patients.