A 38-year-old unmarried woman presents with heat intolerance, hyperhidrosis, and weight loss for over 2 months. Physical exam: Grade I thyroid enlargement, no bruit, heart rate 120/min with regular rhythm. Thyroid iodine uptake: 3h 36%; 24h 90%. After discontinuing medication for 6 months, the patient becomes pregnant (2 months) and reports recurrent palpitations and hyperhidrosis. Repeat tests show elevated FT3/FT4 and TSH 0.01 mU/L (0.01 μU/mL), indicating hyperthyroidism relapse. The best management is: