Radioactive iodine-131 treatment for hyperthyroidism is an effective treatment method that is simple, safe, short-course, fast-acting, with high one-time cure rate, low recurrence rate and low cost. Hyperthyroidism (short for hyperthyroidism) is a very common endocrine disease. It is a clinical syndrome in which excessive secretion of thyroid hormones causes increased excitability and hyper-metabolism in the nervous, circulatory and digestive systems of the body. The incidence rate is about 1%, and it is more common in women, with a male to female ratio of about 1:4-6. It can occur in all age groups, with the most common in the 20-40 age group. The etiology and pathogenesis have not yet been fully elucidated. The pathology is diffuse, nodular or mixed goiter and a variety of organ and tissue lesions caused by hyperthyroidism, including a series of pathophysiological changes that occur due to excessive thyroid hormones acting on various organs throughout the body. There are many types of hyperthyroidism, but the common feature is excess thyroid hormones. Patients with hyperthyroidism may experience some conscious symptoms, such as panic, rapid heartbeat, fear of heat, excessive sweating, hyperphagia, increased bowel movements, menstrual disorders, irritability, impatience, fatigue, and weight loss, etc. Some patients may also find themselves with thickened neck and protruding eyes. If the above symptoms and signs appear, it is likely that the patient is suffering from hyperthyroidism and should go to the hospital for relevant examinations in time to make a clear diagnosis. In hospitals, doctors usually arrange for serum T3, T4 (including TT3, TT4, FT3, FT4) and thyroid stimulating hormone (TSH) tests and thyroid scans to understand the shape, location, size, presence or absence of nodules and function of the thyroid gland. The diagnosis of hyperthyroidism can be basically confirmed if increased T3 and T4 levels (some people have only 1 increase), decreased TSH levels and diffuse enlargement or toxic thyroid adenoma are found. If the serum T3 and T4 levels are not significantly increased, further iodine uptake rate of the thyroid gland and thyroxine suppression test and thyroid hormone releasing hormone (TRH) excitation test can be done, which are helpful in the diagnosis of atypical hyperthyroidism. Patients suffering from hyperthyroidism need not panic. There are four kinds of treatment methods in common use: internal anti-hyperthyroidism medication, surgery, radioactive iodine treatment and Chinese herbal medicine. Internal treatment refers to the use of anti-thyroid drugs, such as tabazol, hyperthyroidism, methylthioxypyrimethamine, propylthioxypyrimethamine, etc., which mainly play the role of inhibiting the synthesis of thyroid hormones. This is a commonly used method with positive efficacy and easy method. The disadvantage of this method is the long duration of treatment, which requires at least two years of regular medication, and the high relapse rate (up to 50%) after stopping medication. Surgery is also a treatment for hyperthyroidism, and is particularly effective for toxic thyroid adenomas. If the adenoma is removed cleanly, there is usually no recurrence of hyperthyroidism in the future. The disadvantage is that after all, it is a surgical procedure and carries certain risks, leaving scars on the neck after surgery, and a high recurrence rate (30%), especially in diffuse hyperthyroidism with enlargement of the thyroid gland. Treatment with radioactive iodine is currently recognized worldwide as an effective method. The former president of the United States, George H.W. Bush, suffered from hyperthyroidism during his administration. After consultation and discussion with many world-class medical experts, the final treatment plan was to use radioactive treatment, and received good results. It is now included as the preferred method in many Western countries. Why is isotope therapy so effective? Because iodine is a necessary raw material for the synthesis of thyroid hormones in the thyroid gland, and radioactive iodine and stable iodine have the same physiological and biochemical properties, so the thyroid tissue also has a high absorption and concentration capacity for radioactive iodine. In general, the concentration of iodine in the thyroid gland can reach 25 times of the plasma concentration. In patients with hyperthyroidism, the rate and amount of synthesis of thyroid hormones increase, so the concentration of radioactive iodine is even higher, up to 90%. The effective half-life of iodine in the thyroid gland is 3.5 to 4.5 days on average. The large amount of concentrated radioactive iodine exposes the thyroid gland to radiation, which partially destroys the thyroid tissue, resulting in a decrease in thyroid hormone production and remission or cure of hyperthyroidism. Iodine-131 is an unstable radioactive radionuclide that emits γ and β rays during the decay process, with β rays accounting for 99% of the therapeutic effect. Because beta rays have a short range of 1 mm on average and 2.2 mm on the longest, they can destroy thyroid tissues, but have little or no effect on the surrounding tissues and organs. This shows that radioactive iodine is a safe and easy way to treat hyperthyroidism. Who is suitable for radioactive iodine treatment for hyperthyroidism? It is generally accepted that both male and female adult patients are suitable for iodine-131 treatment. There is some debate about the treatment of women of childbearing age and children. In the early days of iodine-131 treatment for hyperthyroidism, there were concerns about the risk of cancer, leukemia, and congenital abnormalities in the fetus. After half a century of clinical practice, it has been proved that these concerns have been eliminated. Statistics of more than one million patients at home and abroad show no increase in the incidence of leukemia and thyroid malignancies, no more than natural incidence of fetal malformations, and no effect on fertility and offspring development. These have been extensively reported in the literature. It is now unanimously accepted by experts that treatment with iodine-131 is contraindicated in patients with hyperthyroidism during pregnancy and lactation because it can cause hypothyroidism in the fetus or infant. Therefore, we believe that iodine-131 is a safe form of treatment for patients of all ages (including women and children of childbearing age), except for pregnant and lactating women, and should be the treatment of choice for adults. Treatment of hyperthyroidism with radioactive iodine is usually performed in the nuclear medicine department. The nuclear medicine doctor decides the time and dosage of radioactive iodine based on a comprehensive analysis of the patient’s hyperthyroidism symptoms, clinical manifestations, laboratory test results, thyroid gland iodine absorption function and thyroid scan results. Generally speaking, after the diagnosis of hyperthyroidism is confirmed, some preparatory work should be done before treatment with iodine-131, such as controlling certain heavier complications and abstaining from iodine-containing foods or medications. Before and after taking iodine-131, some auxiliary therapeutic agents should be dispensed according to the clinical manifestations, and certain reactions should be noted some time after taking the drug. Most of the patients can be controlled after treatment, and a cure can be achieved with a single dose of the drug. A small number of patients require a second treatment. The effect of iodine-131 starts to appear more than 3 weeks after taking it, and within 3 months the symptoms gradually improve, the thyroid gland shrinks and some patients’ proptosis is reduced. 6-12 months the symptoms are completely eliminated. If a second treatment is needed, it should be done after six months, preferably 8 to 10 months apart. Some patients with hyperthyroidism have protruding eyes, which is called proptosis. The causes are complex and may be related to certain immune disorders in the body, and some people have found that there is a substance in the serum of these patients that is related to the occurrence of proptosis. The occurrence and aggravation of proptosis are not parallel to the condition of hyperthyroidism. Most patients with hyperthyroidism will not have their proptosis aggravated by iodine-131 treatment, but only a few cases may have their proptosis aggravated. This should be properly understood. Hyperthyroid patients generally do not have any reaction after taking iodine-131, and only a few patients experience some side effects. Some reactions that occur within 2 weeks after taking the drug are called early reactions, mainly nausea, vomiting, dizziness, weakness, and in a few patients, rash and itching, which are generally mild and can disappear on their own. Some patients may experience transient exacerbation of hyperthyroidism, which is usually temporary, and very few patients with severe symptoms have to be hospitalized for observation. The main complication in the late stage is hypothyroidism (also known as hypothyroidism). It is caused by insufficient synthesis and secretion or physiological effect of thyroid hormones. One type of hypothyroidism caused by iodine-131 treatment is transient hypothyroidism, which is mild and can disappear on its own after 6 to 9 months, because of the recovery of incomplete thyroid cells damaged by radiation or compensatory proliferation of residual tissues. The other type is permanent hypothyroidism, which is reported to occur in 2-5% of the first year, and increases by 2-3% each year as time goes on. After hypothyroidism occurs, normal thyroid function can be maintained as long as the appropriate amount of thyroxine is supplemented under the guidance of a doctor. Some scholars believe that hypothyroidism is a natural history of hyperthyroidism and can occur after various treatments, and is not unique to iodine-131 treatment. In summary, several methods of treating hyperthyroidism have their own characteristics, and it is necessary to develop the correct treatment plan for the individual patient. In contrast, radioactive iodine-131 treatment for hyperthyroidism is widely applicable, simple, safe and effective, with fewer doses, fewer complications, a high cure rate and low cost, and can be the first choice for most patients.