Thyroid cancer usually undergoes surgery to remove all or most of the thyroid tissue and requires lifelong thyroxine treatment after surgery. Indicators of thyroid function are monitored after surgery, mainly including T3, T4, free T3, T4, TSH or serum thyroglobulin measurement. Thyroid cancer is a very common malignant tumor of the head and neck. Generally, serum thyroglobulin assay is mainly used to determine the recurrence of well-differentiated thyroid cancer, and if this index is suddenly elevated more, it suggests a possible tumor recurrence. In addition, abnormal indicators such as thyroxine T3 and T4 suggest that the dosage of Eugenol may need to be adjusted.