A 28-year-old woman presents with heat intolerance, hyperhidrosis, increased appetite, and weight loss for over 2 months. Physical examination reveals bilateral exophthalmos, conjunctival congestion, grade II thyroid gland enlargement, and heart rate 100 bpm. FT<sub>3</sub> and FT<sub>4</sub> are significantly elevated. What is the best treatment for this patient?