The thyroid gland has the ability to concentrate iodine and 131 iodine emits beta rays biologically, causing the destruction and atrophy of thyroid follicular epithelial cells and reducing the synthesis and secretion of thyroxine for therapeutic purposes. Usually the patient only needs one dose, and if it is not effective, another dose can be added after six months or a year. The size of the thyroid gland will gradually decrease after treatment, and a small percentage of patients may develop early or late hypothyroidism (requiring thyroid tablets or thyroxine tablets). It is safe and effective, simple, with a high cure rate and a low recurrence rate. Absolute indications Adult Graves’ hyperthyroidism with goiter II or higher; failure of oral antihyperthyroid medication or allergy or liver damage or granulocytopenia or unwillingness to take long-term medication; recurrence of hyperthyroidism after surgery; hyperthyroid heart disease or hyperthyroidism with other causes of heart disease; hyperthyroidism combined with blood leukopenia and/or thrombocytopenia or complete blood cytopenia; elderly hyperthyroidism; hyperthyroidism combined with diabetes mellitus; toxic multinodular Autonomous functional thyroid nodules in combination with hyperthyroidism. Relative indications Adolescent and pediatric hyperthyroidism, failure or recurrence of treatment with ATD or the presence of side effects, refusal of surgery or contraindications to surgery; hyperthyroidism combined with impairment of liver, kidney and other organ functions; infiltrative proptosis. For mild and stable moderate or severe infiltrative proptosis, 131 iodine alone can be used to treat hyperthyroidism. Contraindications: pregnancy, lactation and acute phase of myocardial infarction.