Hyperthyroidism later became hypothyroidism, the causes of this phenomenon are drug factors, disease factors, surgical factors, etc., the patient should follow the doctor’s instructions, as appropriate, to reduce the anti-hyperthyroidism drugs or take the appropriate dose of thyroid hormone medicine. 1. Drug factors: if patients with hyperthyroidism are taking anti-thyroid medication, the dosage may be too large, resulting in a decrease in thyroid hormones, triggering hypothyroidism, at this time, the patient should consult a doctor in a timely manner, and adjust the original treatment program in accordance with the doctor’s instructions. 2. Disease factors: patients with Hashimoto’s thyroiditis, subacute thyroiditis, and other diseases, the early stage of the disease patients will appear transient hyperthyroidism, and then become hypothyroidism. For patients with Hashimoto’s thyroiditis, hypothyroidism needs to be treated by taking levothyroxine tablets; subacute thyroiditis is a self-limiting disease, and usually requires no special treatment. 3. Surgical factors or radioactive iodine treatment: If hyperthyroidism patients undergo thyroidectomy or radioactive iodine treatment, it can also cause hypothyroidism, and the patient should take levothyroxine and other drugs as prescribed by the doctor for life to maintain the body’s thyroxine level. It is recommended that patients go to the hospital in time to identify the cause of the disease and receive treatment as soon as possible.