Comparison of two commonly used antithyroid drugs (ATD), methimazole (MMI) and propylthiouracil (PTU): 1. Both have similar mechanisms of action, inhibiting thyroid peroxidase, a key enzyme in thyroid hormone synthesis, and both have mild immunosuppressive effects; 2. PTU has a short half-life (1h) and is retained in the PTU has a short half-life (1h) and is retained in the thyroid gland for a short period of time, so it needs to be administered once every 6-8 hours, and the patient’s compliance is poor, while MMI has a long half-life (4-6h) and is retained in the thyroid gland for up to 24 hours, so it can be administered once a day with good compliance. PTU is preferred for early hyperthyroidism, severe hyperthyroidism and hyperthyroidism crisis, and MMI is preferred for maintenance treatment of hyperthyroidism; 4. Both PTU and MMI have less amount to pass through the placenta, but PTU has less effect on the fetus, therefore, PTU is preferred for drug treatment of combined hyperthyroidism in pregnancy; 5. MMI is more likely to cause leukocyte drop than PTU, and PTU is more likely to cause liver function damage than MMI.