Taking radioactive 131 iodine to treat hyperthyroidism is convenient to use, has a high one-time cure rate, and is low cost, which is popular among patients. However, some people worry that radiation is harmful and can hurt people’s vitality, cause infertility, etc. What are the facts? We should have a proper understanding of it. The common self-perceived symptoms of hyperthyroidism patients are panic, rapid heartbeat, fear of heat, excessive sweating, short temper, weakness, weight loss, hyperphagia, and increased stool. Some patients may also find themselves with thickening of the neck and protruding eyes. If the above symptoms and signs appear, you should go to the hospital for relevant examination in time. Patients suffering from hyperthyroidism need not panic, as the disease is completely curable. However, it is different from a cold or flu that will be cured within a few days, there is a process. There are three kinds of treatment methods in common use: internal anti-hyperthyroidism medication; surgery; and radioactive iodine 131 treatment. Internal treatment refers to the use of anti-thyroid drugs, such as tabazol, hyperthyroidism, methylthioxypyrimethamine, propylthioxypyrimethamine, etc., which are used to inhibit thyroid hormone synthesis and are effective and simple. The disadvantage of this treatment is the long duration of treatment, which requires at least one and a half years of medication, and the high recurrence rate after stopping medication, which can be more than 50%. Surgery is the most effective treatment for toxic thyroid adenoma. If the adenoma is cleanly removed, there is usually no recurrence of hyperthyroidism in the future. The disadvantage is that it is a surgical procedure after all, which carries certain risks and has a high recurrence rate (30%). Treatment of hyperthyroidism using radioactive 131 iodine is now recognized worldwide as an effective method. When former U.S. President George W. Bush was suffering from hyperthyroidism during his administration, he was finally treated with this method after consultation and discussion by many world-class authoritative medical experts, and received good results. Currently, it is included as the preferred method in some Western countries. Why is isotope therapy so effective? Radioactive 131 iodine has the same physiological and biochemical properties as stable iodine, and the thyroid gland tissue has the same high absorption and concentration capacity for it. Large amounts of concentrated radioactive 131 iodine expose the thyroid gland to radiation, which partially destroys the thyroid tissue, resulting in a decrease in thyroid hormone production and the remission or cure of hyperthyroidism. 131 iodine is an unstable radionuclide that emits γ and β rays during the decay process, with β rays accounting for 99% of the therapeutic effect. Because of the short range of β-rays, 1 mm on average and 2.2 mm on the longest, they have little or no effect on the tissues and organs surrounding the thyroid gland. This shows that radioactive 131 iodine is a safe and easy way to treat hyperthyroidism. Who is suitable for radioactive iodine treatment for hyperthyroidism? It is generally accepted that radioactive iodine therapy is suitable for adult patients of both sexes. The treatment of women of childbearing age and children is a matter of debate. In the early days of using 131 iodine to treat hyperthyroidism, there were concerns about the risk of cancer and leukemia and congenital abnormalities in fetuses. After half a century of clinical practice, these fears have been eliminated. Statistics from more than 1 million patients at home and abroad show no increase in the incidence of leukemia or thyroid malignancies, no more than natural incidence of fetal malformations, and no effect on fertility and offspring development. It is now unanimously accepted that treatment with 131 iodine is contraindicated in patients with hyperthyroidism during pregnancy and lactation because it can cause hypothyroidism in the fetus or infant. Therefore, we believe that 131 iodine is a safe treatment for patients of all ages (including women of childbearing age and children), except for pregnant and lactating women. Treatment of hyperthyroidism with radioactive 131 iodine is performed in the Department of Nuclear Medicine, and most patients can have their disease controlled after treatment and can be cured with a single dose of the drug. A small number of patients require a second treatment. It takes more than 3 weeks after taking 131 iodine for the treatment to begin to take effect, and within 3 months the symptoms gradually improve, the thyroid gland shrinks, and some patients’ proptosis can be reduced. For those who need a second treatment, it should be done after six months, preferably 8-10 months apart. Some patients with hyperthyroidism have protruding eyes, the cause of which is complex and may be related to certain immune disorders in the body. Some patients have been found to have a substance in their serum that is associated with the development of proptosis. Only a few cases of proptosis may be aggravated by 131 iodine treatment, and this should be properly understood. Only a few patients have early reactions within 2 weeks after taking 131 iodine, mainly nausea, vomiting, dizziness and weakness; a few patients have skin rash and itching, which are generally mild and can disappear on their own. Late complications are mainly hypothyroidism, which is caused by insufficient synthesis and secretion or physiological effect of thyroid hormones. 131 iodine treatment causes transient hypothyroidism, which is mild and can disappear on its own after 6-9 months. Another type of hypothyroidism is permanent hypothyroidism, the incidence of which is reported to be 2% to 5% in the first year in China, and increases by 2% to 3% year by year as time goes on. Hypothyroidism is not scary, as long as the right amount of thyroxine is supplemented, normal thyroid function can be maintained. Some scholars believe that hypothyroidism is a natural history of hyperthyroidism and can occur after various treatments and is not unique to 131 iodine treatment.