Transthyretin (TTR) is a plasma transport protein for thyroxine and retinol,through the association with retinol-binding protein. It is a homotetrameric protein synthesized mainly in liver,choroid plexus,retinal pigment epithelium,and pancreas.Within the CNS,TTR is the only known protein synthesized solely by the choroid plexus. Mutant and wildtype TTR give rise to various forms of amyloid deposition (amyloidosis). Defects in TTR are the cause of amyloidosis transthyretin-related (AMYL-TTR),hyperthyroxinemia dystransthyretinemic euthyroidal (HTDE) and carpal tunnel syndrome type 1 (CTS1). In addition,positive immunostaining for TTR has been reported as a sensitive diagnostic marker of choroid plexus tumors. (22103483)