A

Transthyretin is a plasma protein that transports thyroxine and retinol-binding protein but plays no role in iron handling, whereas ceruloplasmin (a ferroxidase), the iron-regulatory hormone hepcidin, and the iron exporter ferroportin are all central components of iron metabolism [Saraiva et al., 2005, PMID 16236271; Kono et al., 2010, PMID 20655381; Nemeth & Ganz, 2021, PMID 34204327].