Transthyretin, TTR also designated prealbumin,is a major thyroid-hormone binding protein involved ni transporting thyroxine from the bloodstream to the brain. Sequence variants of this protein have been identified in amyloid fibrils from patients with familial amyloidotic polyneuropath (FAP), the most common form of hereditary ststemic amyloidosis. Prealbumin is most abundantly expressed in the choroids plezus and is also found in the liver