question: What is the function of transthyretin in cerebrospinal fluid?
answer: Transthyretin (TTR) is a protein synthesized in the choroid plexus, which forms the blood-cerebrospinal fluid barrier.  TTR is the physiological carrier of thyroxine (T4) and retinol from the blood into the cerebrospinal fluid and their distribution in the brain. The transport of T4 is important for normal development of the brain.