# What Is Melanotan 2? The Melanocortin Peptide Explained > What is Melanotan 2: a cyclic, truncated analog of alpha-MSH and a non-selective melanocortin agonist. The structure, the names, the receptors, and the honest status. A seven-residue ring, built to outlast the hormone it imitates — described from its structure to its receptors. ## In plain words What is Melanotan 2? It is a lab-made peptide — a short chain of amino acids closed into a ring — that copies a natural body signal called alpha-MSH, the messenger that tells skin to make pigment. Because it is built as a ring, it lasts far longer in the body than the natural signal, which the body breaks down fast. Injected under the skin, it pushes pigment cells to darken the skin without sun. But the same signal touches more than skin: it dampens appetite and, in men, drives erections. People call it Melanotan 2, Melanotan II, MT-2, or MT-II. It is not a medicine — no regulator has approved it for anything — and the version sold online is an unregulated research chemical of unknown purity. Below is the plain structure and biology, then the honest status. ## Melanotan: the name and the family The word 'melanotan' covers a small family of synthetic copies of alpha-MSH. There are two originals: Melanotan I — the linear analog, relatively selective for the pigment receptor MC1R — and Melanotan 2, the cyclic, truncated version that reaches all the melanocortin receptors [3]. A third compound, a spin-off optimized away from pigmentation and toward sexual effects, grew out of the same scaffold [3]. They are related but not interchangeable: Melanotan I has a regulatory approval that Melanotan 2 does not, for a rare light-sensitivity disorder, and the sexual-function spin-off has its own separate approval — neither approval applies to Melanotan 2 [3]. ## Mt2: structure and identity Mt2 — Melanotan 2 — is a cyclic (lactam-bridged) heptapeptide analog of alpha-MSH, sequence Ac-Nle4-cyclo[Asp5-His6-D-Phe7-Arg8-Trp9-Lys10]-NH2, a truncated, cyclized, D-Phe-substituted derivative of the alpha-MSH core designed by Hruby and Hadley in the late 1980s [1][7]. Its molecular formula is C50H69N15O9 and its molecular weight is about 1024.2 daltons (a dalton is the unit of molecular mass); its CAS registry number is 121062-08-6. The lactam bridge — an internal amide bond clasping two side chains into a ring — is the key design move: it constrains the shape, raising potency and resistance to enzymatic breakdown relative to the linear hormone [7]. ## Melanotan ii: which receptors it binds Melanotan II is a non-selective agonist of the melanocortin receptors, reaching MC1R through MC5R [8]. MC1R governs pigmentation; MC4R (with MC3R) governs appetite and sexual function; MC3R governs energy balance; MC5R is linked to gland function [8]. This breadth is the whole story of the compound: a single key that opens five locks, which is why a tanning agent also suppresses hunger and triggers erections. The full signal path is detailed under [melanotan 2 mechanism of action](/mechanism-of-action). ## Where Melanotan is derived from or made Melanotan 2 is entirely synthetic — it is not extracted from any animal or plant. It is built by peptide synthesis as a designed analog of the body's own alpha-MSH, a thirteen-amino-acid peptide cut from the larger precursor protein proopiomelanocortin (POMC) and produced in the pituitary and the skin [8]. The first preparative solution-phase synthesis of Melanotan 2 has been published, and the molecule is made to order in laboratories [7]. The crucial caveat: material sold online is made without oversight, and forensic analyses repeatedly find inaccurate labeling and variable content [14]. ## The honest status Melanotan 2 holds no approved indication in any jurisdiction [1]. It is handled as a research chemical, and selling it for human use is unlawful. Regulators including the US FDA, Australia's TGA, the UK's MHRA, and Ireland's HPRA have warned against tanning products containing melanotan [26]. As a non-approved substance with performance- and physique-altering effects, it also falls under WADA's S0 category and is prohibited in sport at all times. None of this is incidental — it is part of what Melanotan 2 is. --- A cinematic reading of one peptide's published record — its light and its shadow, cited; not a clinic, not a vendor, not a prescription.