1. Reasons for medical safety: There are certain medical risks during iodine-131 treatment after thyroid cancer surgery, which require hospitalization for observation and the management and prevention of complications after iodine-131 treatment. For example, some patients may experience neck discomfort, and even some patients may experience respiratory difficulties due to more residual thyroid tissue and neck enlargement compressing the trachea and laryngeal edema after iodine-131 treatment. Some patients develop a sharp decrease in white blood cells, and some develop acute gastroenteritis and other clinical discomforts that require management and prevention. In addition, some patients need to be hospitalized for observation when combined with other high-risk diseases, so as to avoid aggravation of other high-risk diseases during iodine 131 treatment and the existence of medical safety risks. 2. Reasons for radiation safety: Iodine 131 treatment is to use the thyroid gland’s ability to concentrate iodine, and the given iodine 131 can release beta rays, which can exert radiation biological effects locally to cause destruction and atrophy of thyroid follicular epithelial cells and thyroid cancer cells and reduce secretion to achieve the effect of treating hyperthyroidism or residual thyroid cancer, which is currently one of the important means to treat hyperthyroidism and residual thyroid cancer lesions after surgery. It is one of the important tools for the treatment of hyperthyroidism and postoperative residual thyroid cancer. However, since radioactive iodine 131 not only releases β-rays but also emits γ-rays, which have certain penetrating ability and may cause radiation hazards to patients themselves and their family members, health care workers and other normal people around them, it is necessary for patients to take shielding isolation measures for a certain period of time when high-dose iodine 131 treatment is performed. In addition, there is a large amount of radioactive excretion in the early days (especially within the first 1-3 days) when the patient is treated with iodine 131, and this excretion needs to be treated with a special radioactive sewage treatment system, otherwise it will cause contamination of the surrounding environment. Therefore, patients with hyperthyroidism or thyroid cancer treated with high doses of iodine 131 require short-term hospitalization for radiation safety isolation as well as radiation-borne excretion disposal in order to protect the community at large and reduce radiation contamination of the surrounding environment.