This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Vitamins and Minerals, Subject name: Biochemistry
All of the following proteins are involved in the metabolism of iron, EXCEPT 
Select and explain. 
A. Transthyretin, B. Ceruloplasmin, C. Ferritin, D. Hepcidin
A: Transthyretin
Answer: A: Transthyretin 
Explanation: Transthyretin (formerly known as prealbumin) binds to T4 and forms a complex with retinol-binding protein. It is not involved in iron metabolism. Don't confuse it with Transferrin Ceruloplasmin is a copper containing ferroxidase oxidises any ferrous iron to ferric iron and Aceruloplasminemia leads to hemochromatosis Hepcidin is the main regulator of systemic iron homeostasis Ferritin-is an iron containing protein