AbstractThe syntheses and biological activities of 4 analogues of the thyrotropin‐releasing hormone (TRH) are described. In these analogues the histidine residue has been replaced byL‐lysine,L‐α,γ‐diaminobutyric acid, β‐(3‐pyrazolyl)‐L‐alanine, and L‐arginine. All analogues exhibited the characteristic biological responses of TRH. For the β‐(3‐pyrazolyl)‐L‐alanine analogue as well as for TRH the bioassays suggest an induction of a strong and rapid resynthesis of thyrotropin (TSH)