Free practice questions

Question 1 of 10

An 11-year-old girl has had 1 year of fatigue, constipation, weight gain and cold intolerance. Her height has fallen from the 50th to the 5th percentile. She has a firm, nontender, diffusely enlarged thyroid. TSH is markedly elevated, free thyroxine is low, and anti-thyroid peroxidase antibodies are strongly positive. Which of the following is the most appropriate treatment?