Review Question - QID 216593

A 55-year-old man presents to his primary care physician with persistent symptoms of depression. He started taking fluoxetine 3 weeks ago when he was diagnosed with major depressive disorder after a divorce. Since then, he notes that his symptoms are roughly unchanged. His other medications include albuterol. His temperature is 99.3°F (37.4°C), blood pressure is 132/88 mmHg, pulse is 77/min, respirations are 14/min, and oxygen saturation is 99% on room air. Physical exam reveals a depressed affect. His neurologic exam is non-focal. A serum thyroid stimulating hormone (TSH) resulted from his last visit and is noted to be 4.8 µU/mL (normal: 0.5-5 µU/mL). Which of the following is the most appropriate next step in management?