Subchapter 16C – Endorphin

β-END is an opioid peptide secreted from both corticotropes and melanotropes in the pars distalis and pars intermedia in the pituitary. β-END is substantially acetylated at the N-terminus in the pars intermedia. β-END peptides are generated from a precursor protein called proopiomelanocortin by posttranslational proteolytic cleavage. The presence of β-END in the pars distalis of the human pituitary is still controversial. β-END is also produced in other tissues, such as the hypothalamus. β-END preferentially binds to the μ-opioid receptor, whereas N-acetylated forms do not bind to the receptor. β-END is also related to the functions of peripheral tissues such as the cardiovascular and immune systems, in addition to having central effects.