MSH

MSH (melanocyte-stimulating hormone) is a family of peptide hormones derived from POMC (pro-opiomelanocortin). The most-studied member is alpha-MSH, which acts on the melanocortin receptor family (MC1R through MC5R) to regulate pigmentation, appetite, sexual function, and inflammation.

Synthetic MSH analogs — Melanotan I (afamelanotide) and Melanotan II — bind multiple melanocortin receptors and are studied for their effects on pigmentation (MC1R-mediated) and, in the case of MT-II, for sexual response (MC3R / MC4R-mediated). PT-141 (bremelanotide) is a more selective MC4R agonist developed specifically for sexual-response indications.

Melanocortin signaling overlaps with appetite regulation in the hypothalamus, which is why MSH analogs sometimes produce anorectic side effects. The system is also implicated in inflammatory regulation via MC1R on immune cells.