1. In order to maintain thyroid function and prevent tumor recurrence after surgery, differentiated thyroid cancer needs to take Eugenol for life; while medullary carcinoma and undifferentiated carcinoma take Eugenol for life after surgery to maintain thyroid function in normal range. 2.Differentiated thyroid cancer must take Eugenol to prevent recurrence, so that the level of thyroxine in the body reaches the stage of subclinical hyperthyroidism (thyrotropin is maintained below 0.05) to be able to play a role. 3. During pregnancy, both the mother and the fetus need thyroxine, and the amount of thyroxine needs to be increased by 30-50%. If the thyroid gland is hypothyroid, it is prone to infertility and miscarriage. This is similar to maintaining thyroid function at the subclinical hyperthyroid stage in order to prevent tumor recurrence.