The structure of the thyroid hormone distributor protein, transthyretin, has been highly conserved during the evolution of vertebrates. Over the last decade, studies into the evolution of transthyretin have revealed the exis-tence of a transthyretin homolog, transthyretin-like protein, in all king-doms. Phylogenetic studies have suggested that the transthyretin gene in fact arose as a result of a duplication of the transthyretin-like protein gene in early protochordate evolution.
