Iodine-induced hyperthyroidism, also known as iodine-induced thyrotoxicosis, refers to hyperthyroidism associated with increased iodine intake. There are three scenarios in which hyperthyroidism can occur: 1. Iodine-induced hyperthyroidism can result from a single or multiple high-dose iodine intake, such as taking iodine-containing medications like Cordarone or using iodine-based contrast agents. This can happen in individuals with normal iodine levels, but those with nodular goiter are more susceptible. 2. Higher doses of iodine intake, often seen in iodine-rich areas, can lead to iodine-induced hyperthyroidism due to prolonged exposure to elevated iodine levels. 3. Normal doses of iodine, within the physiological range, can cause hyperthyroidism, particularly in iodine-deficient regions. This includes patients with goiter who start taking iodized salt, as well as those in non-iodine-deficient areas with goiter or patients with previously controlled hyperthyroidism who experience a relapse after iodine intake. These three categories represent the primary causes of iodine-induced hyperthyroidism.