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: Medicine
Schilling's test may be used to establish a diagnosis of : 
Select and explain. 
A. Intrinsic factor deficiency, B. Pancreatic Endocrine dysfunction, C. Megaloblastic anemia from folic acid deficiency, D. All of the above
A: Intrinsic factor deficiency
Answer: A: Intrinsic factor deficiency 
Explanation: Answer is A (Intrinsic factor deficiency) Shilling's test is typically done to determine the cause of cobalamine malabsorption (Vitamin B12 malabsorption. A diagnosis of Intrinsic factor deficiency can be established if radiolabelled cobalamine (Vitamin B12) appears in urine after administration of Intrinsic factor. Schilling test is abnormal in conditions that affect cobalamine absorption including Intrinsic Factor Deficiency in Pernicious anemia, Exocrine Pancreatic Dysfunction in Chronic Pancreatitis, Bacterial overgrowth syndrome and Ileal dysfunction.