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: Biochemistry
[{'content': 'Progesterone is synthesized from \nSelect and explain. \nA. Pregnenolone, B. 17-Hydroxypregnenolone, C. Pregnanediol, D. Pregnanetriol', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Pregnenolone is conveed to progesterone by the action of two smooth endoplasmic reticulum enzymes, 3a-hydroxysteroid dehydrogenase (3a-OHSD) and D5,4-isomerase.Ref: Harper&;s Biochemistry; 30th edition; Page no: 503', 'role': 'assistant'}]