Although iodine-131 is an effective treatment for hyperthyroidism, the outcome varies from patient to patient. Some patients do not achieve the desired effect with a single treatment, while others may develop hypothyroidism and require short-term or long-term thyroid hormone replacement therapy. In addition, most hyperthyroidism comorbidities improve gradually with remission of hyperthyroidism, while others require other adjuvant treatments. Therefore, patients with hyperthyroidism should be reviewed and followed up regularly after iodine-131 treatment in order to detect and manage problems in a timely manner. The duration of follow-up and follow-up examinations vary among patients with hyperthyroidism. Mild to moderate hyperthyroidism (those without serious comorbidities) can be followed up within one to three months after treatment to initially evaluate the efficacy of treatment. If it is determined that the patient is clinically cured, the follow-up interval can be extended to once a year. The follow-up examinations include: (1) changes in symptoms and signs of hyperthyroidism; (2) changes in laboratory tests such as FT3, FT4, TSH and, if necessary, T3, T4, TPOAb, TgAb and TRAb, ultrasonography and other tests. Usually, within 6 weeks after iodine-131 treatment, hyperthyroidism patients show significant remission and a significant reduction in thyroid volume (significant reduction in neck enlargement), which is the most remarkable sign of iodine-131 treatment. At this time, however, serum thyroid hormone levels may still be high and TSH levels low, and many patients with hyperthyroidism still have a small amount of iodine-131 in their thyroid gland at 6 weeks, so further improvement may follow. Some patients may experience fatigue, drowsiness, weight gain, coldness, cramps, increased menstrual flow and constipation in young and middle-aged women after iodine-131 treatment, which often indicate the possibility of early onset hypothyroidism and should be followed up in a timely manner.