Description

Melanotan (MT) and Melanotan II (MT-II) are both analogs of the alpha-melanocyte stimulating hormone (α-MSH) which is produced within the pituitary gland. Along with other melanocortins, they are responsible for various internal human functions including skin and hair pigmentation, appetite, libido and physical sexual arousal. Whilst these effects have been observed in both sexes, it is worth noting that increases in libido and sexual function are exclusive to MT-II. 

Prompted by ultraviolet (UV) exposure, α-MSH release consequently stimulates production of melanin from the melanocytes within the skin. Melanin, as I'm sure you are aware, is a brown pigment and responsible for the tanning of the skin. Simply put, more α-MSH means more melanin, resulting in greater skin pigmentation.