Transthyretin (TTR) is also known as Prealbumin, ATTR, TBPA, PALB, which belongs to the transthyretin family. Transthyretin / TTR is a serum and cerebrospinal fluid carrier of the thyroid hormone thyroxine (T4) and retinol-binding protein bound to retinol. In cerebrospinal fluid TTR is the primary carrier of T4. TTR also acts as a carrier of retinol (vitamin A) through its association with retinol-binding protein (RBP) in the blood and the CSF. Less than 1% of TTR's T4 binding sites are occupied in blood. TTR misfolding and aggregation is known to be associated with the amyloid diseases.