What is the thyroid gland? The thyroid gland is an important endocrine organ in the human body, located below the thyroid cartilage in front of the neck, on both sides of the trachea, and resembles the shape of a butterfly, connected by two wings (left and right lobes) and the middle part (isthmus), weighing about 20-30 grams, and can move up and down with swallowing. II. What is 131 iodine? 131 iodine (131I) is a radioactive drug, an isotope of iodine, which has the same chemical properties as iodine but differs from ordinary iodine in that it emits gamma rays for imaging and beta rays for treatment, thus playing a diagnostic and therapeutic role. III. What is meant by radioactive iodine therapy (131 iodine therapy)? 131 iodine only accumulates in the thyroid tissue and is not taken up by other tissues. When the thyroid gland is removed, the metastatic foci of thyroid cancer or/and the residual thyroid gland have the function of 131 iodine. When the patient takes a certain amount of 131 iodine (solution or capsule) orally, the residual thyroid gland and metastases can take up 131 iodine to a high degree, and the beta radiation emitted by 131 iodine can effectively remove the residual thyroid tissue and kill the tumor cells. Which thyroid cancer patients need 131 iodine therapy? After total or subtotal thyroid cancer resection, the postoperative pathological type is papillary cancer, follicular cancer or partially hypofractionated cancer. Most patients with thyroid cancer should be treated with radioactive iodine after surgical resection, but postoperative 131 iodine therapy is not recommended for patients with microscopic thyroid cancer without lymph node metastasis and without high risk factors for recurrence. In patients with poor liver and kidney function, low blood count or some patients with advanced severe thyroid cancer such as intracranial hypertension and spinal cord compression due to brain metastasis or bone metastasis, although the cancer lesion can take up and gather a certain amount of radioactive 131 iodine, external radiotherapy is usually required before 131 iodine therapy because 131 iodine therapy may be life-threatening. V. What are the benefits of 131 iodine therapy? 1. 131 iodine can remove the tiny thyroid cancer lesions that are difficult to detect in the thyroid tissue remaining after surgery in order to reduce the recurrence and metastasis rate; 2. 131 iodine-systemic imaging after radioactive iodine treatment can detect new metastases that cannot be detected by other imaging examinations; 3. 131 iodine treatment can monitor the presence of recurrence or metastasis by measuring blood thyroglobulin after 131 iodine treatment, which is both sensitive and accurate and facilitates follow-up. 4. Most of the local or distant metastases (such as lung, bone, brain, etc.) have good results after repeated 131 iodine treatment, which can be seen as the lesions shrink significantly, reduce symptoms and improve the quality of life, and some patients can be cured. VI. Do I need to be hospitalized for 131 iodine treatment? 131 iodine not only releases β-rays, but also emits γ-rays. γ-rays have strong penetrating ability and may cause radiation hazards to the patient himself, the patients in the same ward, as well as to the surrounding medical staff and other normal people. Therefore, inpatient shielding and isolation are required for high-dose 131 iodine treatment. In addition, there is a large amount of radioactive excretion during the early phase of 131 iodine treatment, which requires a special sewage treatment system, otherwise it can seriously pollute the environment. Therefore, the entire early phase of 131 iodine treatment needs to be carried out under radiation isolation conditions. In addition, patients may develop various complications while receiving high doses of 131 iodine treatment, and hospitalization allows early detection and treatment to reduce accidents.