Some melanocortin receptors drive appetite. We've known this for decades. Melanocortin receptor 1 controls skin darkening and natural skin color. We've known t

Some melanocortin receptors drive appetite. We've known this for decades. Melanocortin receptor 1 controls skin darkening and natural skin color. We've known this for decades. Sunlight exposure triggers broad-spectrum melanocortin stimulating hormones. We've known this for decades. *Specifically: alpha-melanocyte stimulating hormone, beta-melanocyte stimulating hormone, and gamma-melanocyte stimulating hormone. They're all byproducts of proopiomelanocortin. Adrenocorticotropic hormone is a coproduct of some melanocyte stimulating hormones, and can optionally be cleaved into more melanocyte stimulating hormones.