Thyroid cancer is the fastest growing solid malignancy in the last 20 years, with an average annual growth rate of 6.2%. Currently, it is the 5th most common malignant tumor in women. It may be due to dietary factors (high iodine or iodine deficiency diet), history of radiation exposure, increased estrogen secretion, genetic factors, or other benign thyroid diseases such as nodular goiter, hyperthyroidism, thyroid adenoma and especially chronic lymphocytic thyroiditis. (1) Papillary carcinoma: It accounts for about 85% of thyroid carcinoma, mainly from lymphatic metastasis, and has low malignancy. (2) Follicular carcinoma: It accounts for 8-10% of thyroid cancer, mainly metastases from blood vessels, and is more malignant. (3) Medullary carcinoma: accounting for about 5% of thyroid cancer, metastases from both lymphatic and vascular sources, and is more malignant than the first two. (4) Undifferentiated carcinoma: accounting for 2-3% of thyroid cancer, metastatic from both lymphatic and vascular sources, and highly malignant. Papillary thyroid carcinoma and follicular carcinoma, also known as differentiated thyroidcarcinoma (DTC), account for about 90% of thyroid cancers. It can be treated with iodine 131. In foreign countries, total bilateral thyroidectomy is preferred for differentiated thyroid cancer. Advantages: 1. It can avoid the risk of recurrence of residual thyroid gland after surgery and the risk of second surgery; 2. Iodine 131 therapy can be performed after total thyroidectomy, which can help to eliminate the thyroid gland completely and facilitate the measurement of serum thyroglobulin (Tg) level to detect the recurrence. However, it must be noted that due to different medical systems, the scope of thyroidectomy for differentiated thyroid cancer is somewhat different among physicians in China, as foreign physicians can be more daring in performing more thorough thyroid surgery for longer-term survival, while domestic physicians are more cautious and reluctant to take too much risk (performing total thyroidectomy increases the risk of damage to the recurrent laryngeal nerve and parathyroid glands). The prognosis for differentiated thyroid cancer is good, and complete surgical resection can achieve a radical result with a ten-year survival rate of about 95%. Even if metastasis occurs elsewhere in the body (more likely sites: lung, brain, bone), thyroid cancer can be treated with iodine 131 after thyroidectomy to achieve remission. Postoperative pathological studies have found that the rate of cervical lymph node involvement in DTC is 20% to 50%, and the rate of micrometastasis is 90%. According to foreign data, the recurrence rate of nail cancer is as high as 32.0% with surgery alone, 11.0% with surgery + oral thyroid hormone, and only 2.7% with surgery + 131 iodine therapy + oral thyroid hormone. According to overseas data, the mortality rate of patients with surgery alone is 3.8-5.2 times higher than that of those treated with surgery + 131 iodine, and the recurrence rate is 4 times higher than that of those treated with surgery + 131 iodine. 131 iodine has an efficiency of 75% in the treatment of metastatic foci of differentiated nail cancer. Complete remission can be achieved in 68% of DTC patients with lymph node metastases and 46% of lung metastases, but only 7% of bone metastases. Therefore, 131 iodine therapy is an essential part of the treatment plan for differentiated nail cancer. According to the latest guidelines and norms for the diagnosis and treatment of thyroid cancer in Europe and the United States, those whose lesions have broken through the envelope or invaded the surrounding tissues or especially those with lymph node metastasis during surgery should be removed as much as possible, and radioactive iodine therapy should be routinely given after surgery to consolidate the curative effect and prevent recurrence. All patients with differentiated nail cancer, such as papillary carcinoma and follicular carcinoma, should be routinely treated with 131 iodine to remove residual thyroid tissue after surgery for long-term benefits; if the metastases have the function of 131 iodine uptake, 131 iodine should also be applied to destroy the metastases. Iodine-131 treatment has the following effects: 1. complete removal of residual thyroid gland to reduce the recurrence and metastasis of thyroid cancer in the future; 2. iodine-131 treatment has both diagnostic and therapeutic functions and can be used for whole body scan to detect and determine whether there are new metastases; 3. after iodine-131 thyroid ablation treatment, blood test for thyroglobulin (Tg) to follow up whether there is recurrence and metastasis. The treatment of differentiated thyroid cancer (DTC) with 131 iodine has a history of more than 60 years, and it has been carried out in China for nearly 50 years. The combination of surgical resection, 131I therapy and thyroid hormone suppression therapy is the ideal treatment option for DTC internationally. After surgery for differentiated thyroid cancer, in order to prevent patients from recurrence, in addition to iodine 131 therapy, one must take Eugenol therapy for life to prevent recurrence. For patients with long-term TSH suppression, a daily intake of calcium and vitamin D should be ensured. Radiotherapy and chemotherapy are very ineffective for thyroid cancer, and radiotherapy is not recommended for patients with DTC, except for local palliative treatment. Radiotherapy may be considered if the patient is older than 45 years old and the cancer is seen to infiltrate outside the thyroid gland by visualization during surgery or if there are microscopic lesions remaining and reoperation is not possible or if the residual thyroid cancer does not respond to radioiodine. Adjuvant chemotherapy is not recommended routinely for patients with DTC. How to supplement and adjust thyroxine (eugenol)? After discharge from the hospital, take 100 micrograms of thyroxine (2 tablets of Eugenol, i.e. 100 micrograms) orally every day, which must be taken on an empty stomach, 20-30 minutes before breakfast, and recheck FT3, FT4 and TSH after 1 month, and again after 3 months, 6 months and 1 year, and adjust the dosage according to the condition of thyroid function. Thyroxine should be taken for life and the dosage may be adjusted during the period, but it should not be stopped. The dosage will be adjusted during pregnancy. Life and diet also require special attention. Studies have found a relationship between iodine, especially a diet high in iodine, and the development of thyroid cancer. It is recommended to avoid a diet high in iodine (not absolutely forbidden by some patients) and avoid seafood, seaweed, nori and other high iodine diets, as well as Chinese herbal medicines such as oysters, kombu, seaweed and summer grass. It is also necessary to get enough rest, avoid fatigue and immunity decline, strengthen nutrition, improve the body’s resistance, and can be properly regulated by Chinese medicine.