# Melanotan 2: The Melanocortin Peptide, Reviewed From the Research > Melanotan 2 is a synthetic non-selective melanocortin-receptor agonist studied for pigmentation, appetite, and sexual function. A plain-English, mechanism-first digest of the published literature, cited. A mechanism-first summary of what the published studies on the melanocortin peptide have actually measured: pigment, appetite, sexual function, and the documented harms. Every quantitative claim is cited. ## The short version **Melanotan 2** is a lab-made copy of a natural body signal called alpha-MSH (a hormone that tells skin cells to make pigment). It is a single small peptide that switches on a whole set of related receptors — the controls for skin color, appetite, and sexual function all at once. That is why people who use it report a tan, less hunger, and changes in sex drive from the same injections. It has never been approved as a medicine or a cosmetic anywhere. The human evidence is thin: a few small early studies in a handful of volunteers. Most of the rest of the data comes from rats and mice. Alongside the reported tan, the published record also includes real harms — darkening and new moles, a few melanoma cases, kidney and muscle injury, and prolonged painful erections. What people actually report, including the downsides, is on [the effects page](/effects). This site summarizes that literature, plainly and with sources. ## What the Melanotan 2 literature has measured Melanotan 2 (Melanotan II, MT-2, MT-II) is a cyclic heptapeptide analog of alpha-melanocyte-stimulating hormone (alpha-MSH), the natural ligand for the melanocortin receptors. It was designed in the late 1980s at the University of Arizona to be a superpotent, enzyme-resistant melanotropic agent [1], [3]. Its defining property is breadth: it is a *non-selective* agonist (an activator) of the melanocortin receptors MC1R through MC5R [11]. One molecule, five switches. That breadth is the through-line of the entire research record. Activating MC1R on pigment cells drives skin and hair darkening without sunlight [1]. Activating MC4R in the brain suppresses appetite [5] and triggers erections [2]. The same compound does all of it, which is both why it interested researchers and why its effects are hard to contain. The controlled human data are limited. A pilot Phase I study in 3 male volunteers produced measurable pigmentation after only five low subcutaneous doses [1]. A placebo-controlled crossover study in 10 men with psychogenic erectile dysfunction produced clinically apparent erections in 8 of 10, with mean tip-rigidity duration of 38.0 minutes versus 3.0 minutes on placebo [2]. No Phase II or Phase III trial of Melanotan 2 itself has ever been completed [1], [3]. ## One receptor family, several effects The melanocortin receptors are a family of five G-protein-coupled receptors. Each governs a different system: **MC1R** controls pigmentation, **MC4R** controls appetite and sexual function, **MC3R** contributes to energy balance, and **MC5R** acts on glands [11]. Because Melanotan 2 activates all of them rather than selecting one, its effects span pigment, food intake, and sexual behavior in the same dose. This is the precise point where Melanotan 2 differs from its better-known relatives. Afamelanotide (Melanotan I) is a more MC1R-selective analog approved for a rare light-sensitivity disorder; bremelanotide (PT-141) was engineered from the Melanotan 2 scaffold toward MC4R-driven sexual effects [3]. The full comparison and the receptor logic behind it are laid out in the [melanotan 2 mechanism of action](/mechanism-of-action) page. ## What this site is — and is not This is an editorial digest. It reads the peer-reviewed Melanotan 2 literature and reports what the studies measured, organized by mechanism and cited to source. It is not a clinic, not a vendor, and not a set of instructions. Melanotan 2 has no approved human use [3]. It carries documented serious harms in case reports — renal infarction [4], rhabdomyolysis, priapism, and melanoma among them. The honest account of those harms sits on the [Melanotan 2 effects](/effects) page, the study-by-study record is on the [Melanotan 2 research](/research) page, and every source is listed on the [Melanotan 2 references](/references) page. Doses appear only as study-design facts, never as guidance. --- An independent, mechanism-first reading of the Melanotan 2 record: the melanocortin pharmacology stated plainly, the small human evidence and the documented harms each cited to source, and no clinic, prescriber, or product behind any of it.