MRCP2-1227
A 30-year-old woman presents to the endocrinology clinic with a complaint of unintentional weight loss of 5kg. She denies any changes in her diet or exercise routine but reports feeling warmer, having trouble sleeping, and experiencing a slight tremor in her hands. Her medical history is significant for depression, which is managed with sertraline. Physical examination reveals a BMI of 24 kg/m², a resting tremor, and a large non-tender goiter without palpable nodules or lymphadenopathy. Laboratory tests show an undetectable TSH and a free T4 level of 39 pmol/l, confirming a diagnosis of hyperthyroidism. What is the most appropriate next step in determining the type of hyperthyroidism in this patient?