TSH suppression therapy after DTC surgery: 1. Overview: 1) TSH suppression therapy refers to the application of thyroid hormones after DTC surgery to suppress TSH at or below the low limit of normal, or even undetectable. The aim is to replenish the deficient thyroid hormone and at the same time inhibit the growth of DTC cells. L-T4 is preferred for medication. The unstable content of dry thyroid tablets may bring TSH fluctuations and should not be taken for a long time. 2) TSH suppression level is closely related to recurrence, metastasis and cancer-related death in DTC, especially for those with high-risk DTC, the association is clearer. cancer-related death and recurrence are increased with TSH>2mU/L. TSH suppression to <0.1 mU/L after high risk DTC was associated with a significant decrease in recurrence and metastasis. Postoperative TSH suppression to 0.1-0.5 mU/L in low-risk DTC resulted in a significant improvement in overall prognosis, but lowering TSH to <0.1 mU/L did not have a greater effect. The growth and proliferation of some hypofractionated DTCs do not depend on TSH, and it is difficult to slow down the progression of the disease by suppressing TSH. 3) Long-term use of supraphysiologic doses of thyroid hormone can cause subclinical hyperthyroidism, especially when TSH <0.1 mU/L needs to be maintained, which may affect the quality of life of patients with DTC and increase the cardiac burden and cardiovascular risk (especially in elderly patients), which can be reversed by reducing the dose. Long-term use of supraphysiologic doses of thyroid hormone increases the incidence of osteoporosis in postmenopausal women and increases the risk of fracture.