Iodothyronine deiodinase is an enzyme that plays a crucial role in the metabolism of thyroid hormones. It helps convert the inactive form of thyroid hormone, thyroxine (T4), into the active form, triiodothyronine (T3). This conversion is essential for regulating various physiological processes, including metabolism, growth, and development. There are three main types of iodothyronine deiodinase: D1, D2, and D3. Each type has a specific function and location in the body. For example, D1 is found in the liver and kidneys, while D2 is primarily in the brain and pituitary gland. D3 is responsible for inactivating thyroid hormones, ensuring a balanced hormonal environment.