Radioactive 131 iodine (131I) therapy is one of the three main treatments for hyperthyroidism (internal anti-hyperthyroidism medication; surgery; radioactive iodine therapy), and is currently widely promoted clinically, also involving the treatment of functionally autonomous thyroid nodules, giant goiter, and differentiated thyroid cancer. It uses the thyroid gland’s ability to highly uptake and concentrate iodine and the biological effect of beta radiation released from 131 iodine on the thyroid gland to reduce thyroid hormone secretion by destroying the follicular epithelium to achieve therapeutic purposes. In addition, it also inhibits the production of antibodies in the lymphocytes of the thyroid gland, which enhances the therapeutic effect. Thus, radioactive iodine therapy is popular among patients because of its rapid, easy, safe, low cost and obvious efficacy. In the United States, it is increasingly used, even in children and adolescents. Some countries even consider radioactive iodine therapy as the preferred modality for GD hyperthyroidism. However, some people are concerned that radiation is harmful, that it can harm the “vital energy” of the person, and that it can cause infertility. What are the facts? We should have a proper understanding of it. Wang Hongjiao, Department of Nuclear Medicine, Siping First People’s Hospital The use of radioactive 131 iodine to treat hyperthyroidism is currently recognized as an effective method in the world. When former U.S. President George W. Bush suffered 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. Why is isotope therapy so effective? Radioactive 131 iodine has the same physiological and biochemical properties as stable iodine, and the thyroid tissue has the same high capacity to absorb and concentrate it. A large amount of concentrated radioactive 131 iodine exposes the thyroid gland to radiation, destroying part of the thyroid tissue, reducing the production of thyroid hormones and relieving or curing hyperthyroidism. 131 iodine is an unstable radionuclide that emits γ and β rays during decay, 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. Which patients with hyperthyroidism are suitable for radioactive iodine therapy? The indications for treatment of hyperthyroidism according to the third edition of the National Advanced Textbook of Nuclear Medicine are: 1 hyperthyroidism, 2 allergy to antithyroid drugs, poor efficacy of antithyroid drugs, or relapse after treatment with antithyroid drugs, 3 unwillingness to undergo surgery, or relapse after surgery, or patients with contraindications to surgery, 4 hyperthyroidism with leukocytopenia or thrombocytopenia, 5 hyperthyroidism with atrial fibrillation, 6 hyperthyroidism with Hashimoto’s disease and poor medical treatment. 6 Patients with hyperthyroidism combined with Hashimoto’s disease who are poorly treated with internal medication and have increased iodine uptake in the thyroid gland. The treatment of women of childbearing age and children is now a matter of debate. At the beginning of the treatment of hyperthyroidism with 131 iodine, there were concerns about the risk of cancer, leukemia, and congenital abnormalities in the fetus. However, according to the statistics of more than 1 million patients at home and abroad, no increase in the incidence of leukemia and malignant thyroid tumors has been found, and fetal malformations do not exceed the natural incidence. It is now unanimously accepted by experts that treatment with 131 iodine is contraindicated in patients with hyperthyroidism during pregnancy and lactation, as it can cause hypothyroidism in the fetus or infant. Over the years patients have been treated with iodine 131 and most patients can have their disease under control after treatment and can be cured with a single dose. 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 tumor shrinks, and in some patients the proptosis can be reduced. 6 months to 2 years for all symptoms to be eliminated. If a second treatment is needed, it should be done after 6 months, preferably 8-10 months apart. 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; some patients may have transient exacerbation of hyperthyroidism, which is usually temporary, and very few patients have to be hospitalized for observation. The radiological thyroiditis may occur, which is seen 7 to 10 days after treatment. Late complications are mainly hypothyroidism, which is caused by insufficient synthesis and secretion of thyroid hormones or physiological effects. 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%-5% in the first year in China, and increases by 2%-3% year by year as time lengthens. Hypothyroidism is not terrible, and normal thyroid function can be maintained with the right amount of thyroxine supplementation. In summary, radioactive 131 iodine treatment for hyperthyroidism has the advantages of wide range of adaptation, simple method, safety and effectiveness, low number of doses, and high cure rate at one time. Over the years, our nuclear medicine department has cured tens of thousands of patients with iodine 131, and the word-of-mouth of the cured patients has made our nuclear medicine department’s thyroid treatment center famous in the northeast provinces, and more and more patients are coming here.