This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrinology, Subject name: Pathology
[{'content': 'Long thyroid stimulating agent is \nSelect and explain. \nA. Antibody to thyroid globulin, B. Antibody to thyroid cell receptors, C. Antibody to thyroxine, D. Antibody to thyroid cells', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Answer is option 2, antibody to thyroid receptors. Thyrotropin receptor (TSHR) antibodies that stimulate the thyroid (TSAb) cause Graves\' hypehyroidism and TSHR antibodies which block thyrotropin action (TBAb) are occasionally responsible for hypothyroidism. Unusual patients switch from TSAb to TBAb (or vice versa) with concomitant thyroid function changes. We have examined case repos to obtain insight into the basis for "switching."', 'role': 'assistant'}]