An 80-year-old woman is admitted to the intensive care unit with sepsis due to a urinary tract infection. While in the ICU she develops atrial fibrillation with rapid ventricular response and is treated with a loading dose of amiodarone. She converts to sinus rhythm and is sent home on amiodarone to prevent recurrences of atrial fibrillation. In the following weeks she develops increasing fatigue, dry skin, and constipation and her internist finds her TSH to be 25. She is in sinus rhythm. What is the best approach in this situation?