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': 'Vitamin D resistant rickets occurs due to all Except \nSelect and explain. \nA. alpha 1 hydroxylase deficiency, B. Renal tubular acidosis, C. Fanconi syndrome, D. Drugs', 'role': 'user'}, {'content': 'Answer: A \nExplanation: The disorder is due to missing or inactive PHEX gene. PHEX inactivates phosphatonins that mediate phosphate wasting. Thus, patients with Vitamin D resistant rickets cannot retain phosphate, leading to renal phosphate wasting. ref - Harrisons internal medicine 20e p2920', 'role': 'assistant'}]