1.Thyroid cancer is divided into differentiated thyroid cancer (papillary or follicular carcinoma), medullary carcinoma and undifferentiated carcinoma. The principle is: differentiated thyroid cancer cells have thyrotropin (TSH) receptor expression on the surface, TSH can stimulate tumor cell growth, and the super physiological dose of L-T4 (eugenol) can inhibit TSH, which can reduce the risk of recurrence. In contrast, undifferentiated carcinoma or medullary carcinoma cells do not have TSH receptor expression on the surface, so it is not necessary to take eugenol to prevent tumor recurrence. Based on the above theory, thyrotropin must be maintained below 0.05 to prevent recurrence of differentiated thyroid cancer, which also plays a role in maintaining thyroid function. In the case of undifferentiated or medullary carcinoma, the purpose of taking eugenol after surgery is not to prevent tumor recurrence, but only to maintain thyroid function at normal levels. The purpose and dose of Eugenol after surgery are different for the two major pathological types and must be treated separately. 4. Eugenol must be taken in the morning after waking up in the morning on an empty stomach, once a day. The dose taken needs to be monitored regularly for nail function.