Melanotan II is a super-potent analogue of the peptide hormone alpha-melanocyte-stimulating hormone (a-MSH) that induces skin tanning. It was originally developed at the University of Arizona to treat intolerance to sunlight. Melanotan 2 plays a role in melanogenesis in protecting the skin from UV light by way of uncanny eumelanin production. There are 5 melanocortin receptors each with a different function. MT2 binds primarily to MC4R and MC1R, and weakly to MC3R.

MC1R is found on the melanocytes, stimulation causes darkening of skin and hair. MC2R is found on the adrenal glands, binding to MC2R promotes secretion of adrenal hormones such as cortisol. MC3R involved in appetite control and energy regulation MC4R stimulation causes changes in feeding and sexual behavior, and also affects male erectile function and energy homeostasis.