Iodine-induced hyperthyroidism (IIH) refers to hyperthyroidism related to increased iodine intake, also known as iodine-induced hyperthyroidism or iodine-induced thyrotoxicosis (IIT). From the perspective of iodine intake, there are three situations in which iodine-induced hyperthyroidism occurs: the first is caused by one or more large doses of iodine intake, such as taking iodine-containing drugs such as amiodarone or using contrast agents. It can occur in people with normal iodine nutrition and is more likely to occur in people with nodular goiter; the second is the intake of higher doses of iodine, which often occurs in high-iodine areas and occurs due to long-term intake of higher doses of iodine; the third is the intake of normal doses of iodine (which can be iodine intake within the physiological range), which is seen in patients with goiter in iodine-deficient areas (including marginal iodine-deficient areas) after taking iodized salt; patients with goiter in non-iodine-deficient areas after taking iodine; and patients with controlled hyperthyroidism who relapse after taking iodine.