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: Physiology
[{'content': 'Which is not a peptide hormone? \nSelect and explain. \nA. Somatostatin, B. Serotonin, C. Neuropeptide, D. Enkephalin', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Somatostatin is a polypeptide hormone.', 'role': 'assistant'}]