What is "transthyretin"

n. A protein found in human blood; specifically, a serum and cerebrospinal fluid carrier of the thyroid hormone thyroxine.

Transthyretin (TTR) is a transport protein in the serum and cerebrospinal fluid that carries the thyroid hormone thyroxine (T) and retinol-binding protein bound to retinol. This is how transthyretin gained its name: transports thyroxine and retinol. The liver secretes transthyretin into the blood, and the choroid plexus secretes TTR into the cerebrospinal fluid.

TTR was originally called prealbumin (or thyroxine-binding prealbumin) because it ran faster than albumin on electrophoresis gels.