A truncated isoform of the thyrotropin-releasing hormone receptor is expressed in the rat central nervous system as well as in the pituitary gland.

Using the reverse transcription-polymerase chain reaction (RT-PCR), a cDNA encoding the entire rat thyrotropin-releasing hormone receptor (TRH-R) was isolated from normal rat pituitary gland mRNA. In addition, a novel truncated isoform of TRH-R which lacks 52 base pairs (bp) in the carboxyl (C-) terminal tail was isolated. This truncation, probably generated by alternate splicing, causes a frame-shift and results in a truncated TRH-R 25 amino acids shorter and with a different C-terminal amino acid sequence than the longer type receptor. This truncated TRH-R mRNA, along with the longer receptor form, was found to be expressed throughout the rat pituitary gland and brain.