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
Increased calcium levels lead to 
Select and explain. 
A. Increased 1,25 dihydroxycholecalciferol, B. Increased 24,25 dihydroxycholecalciferol, C. Decreased calcitonin, D. Increased parathormone
B: Increased 24,25 dihydroxycholecalciferol
Answer: B: Increased 24,25 dihydroxycholecalciferol 
Explanation: 24,25-dihydroxycholecalciferol; a metabolite in calcium metabolism, formed in the kidney from 25-hydroxycholecalciferol by the activation of a 24-hydroxylase.Ref: Ganong&;s review of medical physiology; 24th edition; page no:-379