Transthyretine - a Thyroxine Binding Protein


The thyroid hormones tetraiodothyronine (thyroxine or T4) and triiodothyronine (T3) are essential for a number of metabolic processes. Molecules whose spatial structures allow weak interactions with the polar hormones are generally used as receptors.

Thyroid Hormones

Tetraiodothyronine (Thyroxine)

The tetrameric transthyretine can be considered a thyroxine binding protein. It is found in human blood plasma where it carries out a considerable part of the thyroxine transport. Some 80 % of thyroxine is transported to the brain bound to transthyretine.


There are two binding sites for thyroxine in each tetrameric unit.


Transthyretine also has acceptor sites for retinol (vitamine A).