Hyperthyroidism is mostly treated with internal medicine, as well as surgical removal of part of the thyroid gland and radioactive iodine therapy. Each of these treatments has its own advantages and disadvantages. Small amounts of iodine are required for normal thyroid function, but large amounts can inhibit thyroid hormone synthesis or prevent the release of excess thyroid hormone. Therefore, high doses of iodine can be used to stop the overproduction of thyroid hormones. This is especially true when rapid control of hyperthyroidism is needed, such as during a critical episode of hyperthyroidism or before emergency surgery. However, iodine is not used as a routine or long-term treatment for hyperthyroidism. Propylthiouracil or tabazol are the most commonly used drugs to treat hyperthyroidism, reducing thyroid hormone synthesis and decreasing thyroid function. Both drugs are oral preparations. Treatment is started with a high dose, and later the dose is adjusted according to the level of thyroid hormone in the blood. Thyroid function can usually be controlled within 6 weeks to 3 months. Although high doses provide faster control of symptoms, side effects increase. Side effects include allergic reactions (most commonly rash), nausea, loss of taste, and occasionally suppression of bone marrow cell production. Bone marrow suppression causes a significant reduction in white blood cell counts and leaves patients susceptible to life-threatening infections. Propylthiouracil is safer for use in pregnant women compared to the two drugs because it is less likely to cross the placenta and affect the fetus. Metoclopramide is widely used in Europe and is converted to tabazol in the body. Beta-blockers such as tamsulosin may control some symptoms of hyperthyroidism. Beta-blockers have no effect on thyroid function. Radioactive iodine can destroy thyroid tissue and is therefore used to treat hyperthyroidism. Oral radioactive iodine has a high radioactive activity on the thyroid gland, while it has less effect on other tissues of the body. It is important to get the dose right, so that the thyroid function can be restored to normal but not too low. However, in most cases, radioactive iodine treatment eventually leads to hypothyroidism (low thyroid function) and requires thyroid hormone replacement therapy, with oral thyroid hormone tablets being taken daily to replace the body’s lack of need due to excessive destruction and to restore normal thyroid function. About 25% of patients develop hypothyroidism after 1 year of radioactive iodine treatment, and the prevalence increases significantly after 20 years. The ability of radioactive iodine to cause cancer has not been confirmed. Radioactive iodine is contraindicated in pregnant women because it can cross the placenta and destroy the fetal thyroid gland. Thyroidectomy is the surgical removal of a portion of the thyroid gland. Surgery is suitable for young patients, but also for those with a significantly enlarged thyroid and those with allergies or severe side effects to anti-hyperthyroid medications. About 90% of those who undergo surgery are cured permanently. Surgery can also cause hypothyroidism, and thyroid hormone replacement therapy must be given. Complications are rare and include laryngeal nerve palsy and damage to the parathyroid glands (the small glands behind the thyroid that regulate blood calcium).