A reliable method for the quantification of thyrotropin-releasing hormone (TRH) in tissue and biological fluids

A reliable technique for purification of crude tissue extracts and analysis for TRH by HPLC, TLC, radioimmunoassay and bioassay is presented. We conclude that authentic TRH is present throughout the mammalian brain and accounts for much of the TRH-like immunoreactivity in several peripheral organs, but that it is not present in urine, placenta, or pineal, and its concentration in blood is some 250-fold less than a value obtained from a direct radioimmunoassay of a sample of blood.