The correct use of thyroid hormones (such as eugenol or levothyroxine sodium) for lifelong suppressive therapy after radical surgery and 131 iodine nail clearing therapy in patients with differentiated thyroid cancer plays an important role in reducing recurrence. The mechanism is to use exogenous thyroid hormone feedback to inhibit TSH secretion by the pituitary gland, which in turn plays a role in inhibiting DTC cell growth and reducing recurrence and metastasis of DTC. However, not every thyroid cancer patient has the same degree of inhibition, and the dosage of the drug needs to be controlled according to the patient’s condition (i.e. risk level). 1.Low risk patients: maintain TSH at 0.1-0.5 mU/L for 5-10 years, if there is no sign of recurrence TSH can be adjusted within the normal value. 2. Intermediate-high risk patients should have lifelong TSH <0.1 mU/L. Long-term high intake of thyroid hormone may also bring certain side effects, especially the chance of osteoporosis in post-menopausal female DTC patients increases. Patients with coronary angina and tachyarrhythmias are contraindications to thyroid hormone use. Patients with atherosclerosis, cardiac insufficiency, diabetes mellitus and hypertension should be used with caution and the development of their related diseases should be closely monitored. In elderly or DTC patients with cardiovascular disease, L-T4 should be adjusted gradually from a smaller dose to the required dose.