TSH (thyroid stimulating hormone) suppression therapy is necessary after surgery for differentiated thyroid cancer (papillary and follicular carcinoma). The purpose is to correct the deficiency of thyroid hormones after thyroidectomy on the one hand, and to inhibit the growth of differentiated thyroid cancer cells on the other hand, and most importantly, to inhibit the growth of differentiated thyroid cancer cells. This is because, like normal thyroid tissue cells, differentiated thyroid cancer cells have receptors for TSH 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 inhibition is achieved by feedback inhibition of TSH secretion by the pituitary gland through exogenous thyroxine supplementation (levothyroxine, also known as eugenol, is commonly used in China). TSH suppression levels are strongly associated with recurrence, metastasis and cancer-related death in differentiated thyroid cancer (DTC), and this association is especially clear for those with high-risk DTC. cancer-related death and recurrence rates are increased with TSH >2mU/L. Postoperative TSH suppression to <0.1mU/L in patients with high-risk DTC resulted in significantly lower 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. Of course, those thyroid cancers that do not express TSH, such as undifferentiated carcinomas, medullary carcinomas, and certain hypodifferentiated DTCs, do not inhibit tumor growth even when TSH is suppressed to very low levels. A side effect of TSH suppression therapy is that supraphysiologic doses of thyroid hormone can cause subclinical hyperthyroidism, and long-term TSH suppression can affect the quality of life of DTC patients, increase cardiac burden and myocardial ischemia (especially in elderly patients), trigger or exacerbate heart rate disturbances (especially atrial fibrillation), and lead to an increased risk of cardiovascular disease-related death. The optimal goal of TSH suppression therapy is to reduce the recurrence and metastasis of DTC and to reduce the side effects caused by exogenous subclinical hyperthyroidism. For individuals, there is no uniform standard and patients should be assessed for their risk of tumor recurrence and risk of side effects to adopt individualized treatment goals. The risk of recurrence after DTC is divided into 3 levels: low, medium and high risk. The low-risk group is required to meet all of the following conditions: no local or distant metastases; all visually visible tumors are cleared; the tumor does not invade surrounding tissues; the tumor is not an aggressive histologic subtype and there is no vascular invasion; whole-body iodine 131 imaging is performed after nail clearance and there is no iodine uptake outside the thyroid bed. The intermediate risk group requires one of the following conditions: microscopic detection of soft tissue invasion around the thyroid gland on pathological examination after initial surgery; metastasis of cervical lymph nodes; tumor is an aggressive histological subtype; tumor invades blood vessels; whole-body iodine 131 imaging after nail clearance, with iodine uptake outside the thyroid bed. The high-risk group requires one of the following conditions: tumor invasion of surrounding tissues or organs visible to the naked eye; incomplete tumor resection with intraoperative tumor residue; distant metastases; high serum thyroglobulin (Tg) levels even after total thyroidectomy; and family history of thyroid cancer. The risk of side effects of TSH suppression therapy was similarly divided into 3 strata: low, intermediate and high risk. The low-risk group meets all of the following conditions: young to middle-aged; asymptomatic; no cardiovascular disease; no arrhythmia; no signs or symptoms of adrenergic receptor agitation (fear of heat, excessive sweating, excessive eating, lethargy, agitation); no risk factors for cardiovascular disease (obesity, hypertension, hyperlipidemia, hyperglycemia); no co-morbidities; premenopausal women; normal bone mineral density; no risk factors for osteoporosis. The intermediate risk group required one of the following: middle age; hypertension; signs or symptoms of adrenergic receptor agonism; smoking; cardiovascular disease risk factors (obesity, hypertension, hyperlipidemia, hyperglycemia); perimenopausal women; reduced bone mineral density; and risk factors for osteoporosis. The high-risk group needs to meet any one of the following: patients with clinical heart disease; elderly; postmenopausal women; with other serious diseases. The duration of TSH suppression treatment after DTC was divided into an initial treatment period within 1 year after surgery and a follow-up period of 5-10 years in the low-risk group for recurrence and a lifetime in the medium- and high-risk group. The target of postoperative TSH suppression therapy for DTC patients based on dual risk assessment: ① In the low risk of recurrence-low risk of side effects group (dual low group), the target value is 0.1-0.5 mU/L during the initial treatment period and 0.5-2.0?mU/L during the follow-up period, after which it depends on the thyroid function. If the thyroid function is normal, no treatment is needed. (ii) In the low recurrence-medium to high risk of side effects group, the target value is 0.5-1.0?mU/L during the initial treatment period and 1.0-2.0?mU/L during the follow-up period, after which replacement therapy is administered according to the thyroid function. In the moderate-high relapse-low side effect risk group, <0.1?mU/L for both the initial and follow-up periods, and preferably 0.04?mU/L for the initial period.4 In the moderate-high relapse-moderate to high side effect risk group, <0.1?mU/L for the initial period and 0.1 to 0.5?mU/L for the follow-up period.5 Those with moderate to high side effect risk for TSH suppression therapy should have individualized TSH suppression to The maximum tolerated level close to the target value should be adjusted dynamically, along with the prevention and treatment of cardiovascular disease and osteoporosis. For individual patients, the achievement of the TSH suppression treatment target is achieved gradually by testing TSH while supplementing with Eugenol, which takes about 3 months. The starting dose of Eugenol should be based on the patient's age, concomitant disease, and the extent of thyroidectomy. In total thyroidectomy, 1.5 to 2.5 μg/kg/day is started directly in young patients, 50 μg/day is the initial dose if over 50 years old and if there is no heart disease and tendency, 12.5 to 25 μg/day is the initial dose if the patient has coronary artery disease or other high risk factors, and the dose is increased slowly with a long adjustment period required and close monitoring of the heart is needed. For patients with resection of one lobe of the thyroid and isthmus a corresponding reduction is required, which can be estimated by volume ratio. During the dose adjustment phase, TSH is measured every 4 weeks or so, every 2-3 months for 1 year after reaching the standard, every 3-6 months for 1-2 years after reaching the standard, and every 6-12 months for 2-5 years. If you miss a dose, you should take a double dose until the whole missed dose is made up. Some patients need to adjust the dosage of Eugenol according to the change of TSH level in winter and summer, the dosage should be increased in winter and reduced in summer. Pay attention to the interval of time between taking the medication and other medications. 1 hour between with vitamins and tonic, 2 hours between with iron and calcium containing food or medication, 4 hours between with milk and soy food, 12 hours between with choleramide or lipid lowering resin.