FTH1 and Cowden syndrome 1: Corroborating these experimental findings, patients with CS present with elevated serum ferritin, a heteropolymeric protein complex composed of 24 ferritin heavy/ferritin light (FTH/FTL) subunits that can store and convert Fe2+ into inert Fe3+ through the ferroxidase activity of FTH to counteract the disrupted cellular iron homeostasis [17].