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: Biochemistry
[{'content': 'Form of vitamim D which is measured in serum ? \nSelect and explain. \nA. Cholecalciferol, B. 25 hydroxyvitamin D, C. 1,25 dihydroxyvitamin D, D. 24,25 dihydroxyvitamin D', 'role': 'user'}, {'content': "Answer: D \nExplanation: Ans. is 'b' i.e., 25 hydroxyvitamin DThough, 1, 25 dihydroxyvitamin D (calcitriol) is the active form of vitamin D, its serum measurement does not provide any information about vitamin D status because it is often normal or elevated due to secondary hyperparathyroidism associated with vitamin D deficiency...Measurement of 25 hydroxyvitamin D (calcifedial) in serum provides more accurate information of vitamin D status. The usual values are :-< 20 ng/ml - Deficiency20-29 ng/ml - Insufficiency30-100 ng/ml - Normal> 100 ng/ml - Toxicity", 'role': 'assistant'}]