Thyrotropin-releasing hormone (TRH), also called thyrotropin-releasing factor (TRF) or protirelin, is a tripeptide hormone that stimulates the release of thyroid-stimulating hormone and prolactin by the anterior pituitary. TRH is produced by the hypothalamus and travels across the median eminence to the pituitary via the hypophyseal portal system.

In addition to the brain, TRH can also be detected in other areas of the body including the gastrointestinal system and pancreatic islets. Medical preparations of TRH are used in diagnostic tests of thyroid disorders and in acromegaly.

The sequence of TRH was first determined and the hormone synthesized by Roger Guillemin and Andrew V. Schally in 1969. Its molecular weight is 359.5 Da and its structure is: