This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nutrition & Digestion, Subject name: Biochemistry
All are involved in iron metabolism except: 
Select and explain. 
A. Hepcidin, B. Ferroportin, C. Transthyretin, D. Ceruloplasmin
C: Transthyretin
Answer: C: Transthyretin 
Explanation: Ans. C. TransthyretinHepcidin is the regulator of iron homeostasis. Ferroprotin is their on exporter protein into circulation from intestinal cells. Ceruloplasmin has ferroxidase which convert Fe2+ to Fe3+ so it can serve the purpose of hephaestin in iron metabolism. Transthyretin is a transport protein for Thyroxine and Retinol.