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: Medicine
[{'content': 'Which of the following is the most likely effect of insulin at the cellular receptor level? \nSelect and explain. \nA. stimulating tyrosine kinase, B. binding to ion channels, C. binding to intracellular erb A receptors, D. stimulating guanylate cyclase', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Insulin binding to its receptor stimulates tyrosine kinase activity. Other stimulators of protein kinases include platelet-derived growth factor and epidermal growth factor. Tyrosine phosphorylation results from this interaction. Insulin-resistant states can be caused by pre-receptor resistance (mutated insulin, anti-insulin antibodies) or receptor and post receptor resistance.', 'role': 'assistant'}]