Hypothyroidism can be caused by autoimmune damage, destruction of the thyroid gland, excessive iodine intake, and drug effects. 1. Autoimmune damage: Commonly seen in Hashimoto’s thyroiditis, atrophic thyroiditis, postpartum thyroiditis and other diseases, which may lead to autoimmune damage, thus making the secretion of thyroid hormone too low. 2. Destruction of the thyroid gland: Usually, the thyroid gland is destroyed during surgery of lateral or total removal of the thyroid gland, as well as iodine 131 radiation therapy, resulting in damage to its function, which leads to a decrease in thyroid hormones and hypothyroidism. 3. Excessive intake of iodine: When amiodarone and other drugs with high iodine content are taken for a long period of time for the treatment of the disease, the iodine content of the body may be too high, which may cause the symptoms of hypothyroidism. 4. Drug effects: If long-term use of lithium salts, methylthiouracil, propylthiouracil, carbidazole and other drugs, may lead to the body’s thyroid hormone secretion is too small, and cause hypothyroidism. Hypothyroidism may also be caused by other reasons, such as thyroid cancer, etc. Please consult the hospital in time to avoid delay.