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': 'Bile acid synthesis is autoregulated by the enzyme: \nSelect and explain. \nA. 7-Alpha hydroxylase, B. 11-alpha hydroxylase, C. Acetoacetyl-CoA thiolase, D. Desmosterol reductase reductase', 'role': 'user'}, {'content': 'Answer: A \nExplanation: 11-alpha hydroxylase Conves 11-deoxycoisol to 11-alpha coisol (the 11-alpha isomer of hydrocoisone) Bile acid synthesis is autoregulated by 7-hydroxylase, the initial enzyme in cholesterol degradation Other enzymes are involved in cholesterol biosynthesis. Ref: Harrison, E-18, P-2462.', 'role': 'assistant'}]