It is possible for hyperthyroidism to become hypothyroidism after it has been cured, usually in cases of drug overdose, iodine 131 and surgical treatment. However, not all hyperthyroidism patients will have hypothyroidism after treatment, it should depend on the specific situation. 1. Hypothyroidism caused by medication: Some hyperthyroid patients need to use antithyroid drugs to treat, such as methimazole, propylthiouracil, the use of too large a dose of drugs, hypothyroidism may occur, can be adjusted through the dosage of the drug to alleviate. 2. Hypothyroidism caused by surgical treatment: some hyperthyroidism patients will choose surgical resection to carry out radical treatment, after the surgery due to the destruction of the thyroid tissue, thyroxine secretion is reduced, and then there is a hypothyroidism, this time due to the thyroid gland has been removed, so the need for hormone replacement therapy, you can take levothyroxine sodium. 3. Hypothyroidism after iodine 131 treatment: Iodine 131 treatment also destroys thyroid tissues by radioactivity, and hypothyroidism may also occur. Patients with hyperthyroidism are advised to consult their doctors, improve their examinations and have regular reviews.