PGlu-3-methyl-His-Pro-NH2 TFA (A-42872 TFA), the modified thyrotropin-releasing hormone (TRH) peptide, enhances binding to pituitary TRH receptors and increases stimulation of thyroid-stimulating hormone (TSH) release from the pituitary. The in vitro permeability of PGlu-3-methyl-His-Pro-NH2 TFA through rat skin is increased in the presence of enhancers Ethanol and Cineole.