This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Surgery
[{'content': 'DOC for treating thyrotoxicosis in a pregnant patient? \nSelect and explain. \nA. Methimazole, B. Propylthiouracil, C. Carbimazole, D. Radioactive I-131', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Hyperthyroidism in pregnancy should be aggressively evaluated and treated.\xa0\nIt\xa0is\xa0most\xa0commonly\xa0caused\xa0by Graves\xa0disease ,\xa0but\xa0autonomously\xa0functioning\xa0nodules,\xa0gestational\xa0trophoblastic\xa0disease, thyroiditis, and hyperemesis gravidarum should also be considered.\xa0\nHyperthyroidism is most difficult to control\xa0in the first trimester of pregnancy and easiest to control in the third trimester.\nMethimazole crosses the placenta to a greater degree than propylthiouracil and has been associated with fetal aplasia cutis .\xa0\nTreatment of choice is propylthiouracil.\nRadioiodine should not be used during pregnancy, either for scanning or treatment, because of effects on the fetal thyroid.', 'role': 'assistant'}]