This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: AIIMS 2017, Subject name: Biochemistry
Which is not involved in iron metabolism? 
Select and explain. 
A. Transthyretin, B. Ceruloplasmin, C. Hepcidin, D. Ferropoin
A: Transthyretin
Answer: A: Transthyretin 
Explanation: Transferrin is used for transpoing iron throughout the body BUT Transthyretin (Option a) - transpos Thyroxine & Retinol binding protein. So, it is NOT involved in iron metabolism WITH RESPECT TO OTHER OPTIONS: (Option b) Ceruloplasmin is a Cu containing enzyme also having Ferroxidase activity. Ferroxidase conves Fe +2 to Fe +3 (i.e. Ferrous to ferric). Ferric form of iron is required for transpo by transferrin in plasma. (Option c) Hepcidin regulates iron transpo in circulation. (Option d) Ferritin & Haemosiderin are proteins for iron storage. Haemosiderin has higher iron content than Ferritin.