Melanotan II (MT2) is a stimulating peptide which induces skin tanning. Melanocyte Stimulating Hormones (MSH) are a class of peptide hormones produced in the intermediate lobe of the pituitary gland that stimulate pigment cells (melanocytes) in the skin and hair to produce and release melanin which leads to darker skin and hair. Melanotan II increases melanin production via stimulation of skin pigment cells called melanocytes.