It is very difficult for hypothyroidism to return to normal after iodine 131 treatment. The process of iodine 131 treatment will destroy the thyroid gland, resulting in insufficient synthesis of thyroid hormones, which will easily cause patients to develop radioactive hypothyroidism, which is also the biggest side effect after iodine 131 treatment. Hypothyroidism after Iodine 131 treatment cannot be completely cured, it will be a lifelong disease and patients need to take medication for life. Commonly used drugs such as thyroxine tablets or levothyroxine sodium tablets, the specific use of drugs need to follow the doctor’s instructions. Thyroid function should also be tested regularly to maintain the thyroid function in the normal range. Hypothyroidism after iodine 131 treatment requires prompt medical attention and systematic treatment under doctor’s guidance.