Melanotan II (MT-2) is a synthetic peptide that mimics the natural alpha-melanocyte-stimulating hormone. It activates various melanocortin receptors in the body, primarily to increase melanin production (skin pigmentation), but also affecting sexual function and appetite.

MT-2 is associated with the following effects:

• Skin Tanning: The primary use for which people seek MT-2 is to achieve a darker, longer-lasting tan with less UV exposure. This is particularly appealing for fair-skinned individuals who burn easily, as the increased melanin production provides some degree of photoprotection.
• Sexual Function Enhancement: MT-2 is known for its aphrodisiac effects, increasing libido and improving erectile function in men (sometimes resulting in spontaneous erections) and sexual desire in women. A related drug, bremelanotide (PT-141), was developed based on this effect to treat female sexual dysfunction.
• Appetite Suppression: It can reduce appetite, leading to decreased food intake and potential weight loss, a side effect some users find desirable.