Starting from the 1940s, iodine 131 was widely promoted as the mainstream treatment for hyperthyroidism because of its simplicity and effectiveness. However, as time passed, the phenomenon of hypothyroidism and radiation thyroiditis caused by iodine 131 treatment gradually increased, which caused widespread concern in the medical field. With the emergence of safer and more efficient combined Chinese and Western medicine treatment methods, iodine 131 gradually withdrew from the stage of hyperthyroidism treatment. What is Iodine-131? Iodine-131, also known as radioiodine, is an isotope of iodine. There are 78 neutrons in the atomic nucleus, 4 more than the number of neutrons in the nucleus of the stable nuclide of iodine. Iodine-131 is a product of artificial nuclear fission and does not exist in nature under normal circumstances. This nuclide was contained in the radionuclides released by the nuclear leak in Japan. Second, how does iodine 131 treat hyperthyroidism? In nuclear medicine, iodine 131 is used for thyroid disease treatment in addition to direct use in the form of NaI solution for thyroid function check. The radioactive iodine 131 can destroy a part of the thyroid gland, thus reducing the secretion function of the thyroid gland and curing hyperthyroidism, similar to the purpose of subtotal thyroid surgery. What are the advantages of iodine 131 treatment for hyperthyroidism? 1. The treatment process is relatively easy, usually only one oral dose is needed, and only a few patients need to take it again after 2~4 months of treatment. 2. Compared with anti-thyroid medication, Iodine-131 treatment has a higher remission rate and a lower recurrence rate. 3. The treatment has no significant toxic side effects on other tissues in the body (especially the hematopoietic system and liver system); it does not induce tumors, etc. 4. This treatment is especially suitable for hyperthyroidism with toxic side effects after antithyroid drug treatment (such as peripheral blood picture decline, drug allergy, liver function damage, etc.), hyperthyroidism with serious complications, and hyperthyroidism in which the patient is unable or unwilling to undergo surgery. 4. Some types of hyperthyroidism can never be treated with iodine 131 ①Pregnant and lactating women, when the mother ingests 131 iodine, it can enter the thyroid gland of the fetus or baby through the placenta and breast milk, causing cretinism in the fetus and baby. (2) Huge goiter has already produced tracheal compression symptoms, which are often not easily eliminated after taking 131 iodine, and may be aggravated in some cases. ③Patients with severe heart, liver or kidney failure or active tuberculosis. ④Patients under 25 years of age who have not had children (Note: New 2013 guidelines state that it is contraindicated in children under 5 years of age). ⑤ Patients with severe proptosis, which can be aggravated by iodine 131 treatment.