Iodine-131 radiation therapy can usually treat hyperthyroidism and thyroid cancer, the number of treatments needs to be decided according to the patient’s condition, usually done 1 time, the specific number of treatments is recommended to consult a doctor. The principle of Iodine-131 is that thyroid tissues can ingest the radioactive nuclear substance Iodine-131, and the beta rays it emits can usually be used to treat malignant tumors of the thyroid gland, and reduce the synthesis of thyroid hormones to a certain extent, so as to achieve the purpose of treating hyperthyroidism. 1. Thyroid cancer: Usually the dose of Iodine-131 is relatively large for the treatment of this kind of disease. If after one Iodine-131 treatment, a review in 3 to 6 months reveals that there are still cancer cells or distant metastasis of cancer cells, a second Iodine-131 radiation therapy may be needed. 2. Hyperthyroidism: the dosage of Iodine-131 for this disease is relatively small, the range of beta rays is relatively short, and there is no great harm to tissues other than the thyroid gland, so it is relatively a precise treatment, and the treatment effect of most of the patients is relatively good. To summarize, Iodine 131 radiation therapy can usually treat hyperthyroidism and thyroid cancer, and the number of treatments needs to be decided according to the patient’s condition. It is recommended to go to a specialist in a regular hospital to decide whether or not to undergo Iodine 131 Radiation Therapy and the number of treatments under the doctor’s evaluation.