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: Physiology
[{'content': 'All of the following hormones have receptors on the plasma membrane of target tissues except \nSelect and explain. \nA. Thyrotropin, B. Glucagon, C. Estradiol, D. Insulin', 'role': 'user'}, {'content': 'Answer: C \nExplanation: b-Estradiol; 17b-estradiol; the most potent naturally occurring estrogen in mammals, formed by the ovary, placenta, testis, and possibly the adrenal coex; therapeutic indications for estradiol are those typical of an estrogen.Ref: Ganong&;s review of medical physiology; 24th edition; Page no: 403', 'role': 'assistant'}]