# Melanotan 2: The Melanocortin Peptide, Read by the Numbers > Melanotan 2 is a melanocortin peptide whose sexual-function effects in men were measured before its tanning use spread. The published data, stated plainly and cited. A data-forward reading of the published Melanotan 2 record — the erectile-response trials read first, the half-life and receptor data stated plainly, every figure traced to its source. ## The short version Melanotan 2 (also written Melanotan II, MT-II, or MT-2) is a lab-made peptide — a short chain of amino acids — that copies a natural body signal called alpha-MSH. That signal switches on the receptors (docking points on cells) that control skin color, appetite, and sexual response. So Melanotan 2 does several things at once. The headline most people know is tanning: it darkens skin with little or no sun. But the effect researchers measured first, in small studies of men, was erections. In one controlled study, 8 of 10 men with psychogenic erectile difficulty got usable erections after a single injection [2]. Mice eat less when it reaches the brain [5]. None of this is an approved medicine — Melanotan 2 has no approval anywhere, and the studies are small. The downsides are real and worth knowing up front: nausea, flushing, darkening moles, and — in case reports — serious harm. What people actually report, good and bad, is on the [Melanotan 2 effects](/effects) page. ## What the Melanotan 2 literature has measured Melanotan 2 is a non-selective melanocortin-receptor agonist [3]. In plain terms, it activates the whole melanocortin receptor family — MC1R through MC5R — which is why one peptide drives skin pigment, appetite, and erections at the same time [3][12]. It is a cyclic (ring-shaped) heptapeptide designed at the University of Arizona in the late 1980s as a more potent, longer-lasting copy of alpha-MSH [3][14]. The sexual-function findings came early and they were striking. In a 1996 pilot Phase I study of 3 healthy men, low subcutaneous doses produced skin darkening and spontaneous erections lasting 1 to 5 hours [1]. A 1998 double-blind crossover study then measured the erectile effect directly: in 10 men with psychogenic erectile dysfunction, a single 0.025 mg/kg subcutaneous dose produced clinically apparent erections in 8 of them, with mean duration of firm rigidity reaching 38.0 minutes versus 3.0 minutes on placebo [2]. These are study-design facts, not a dosing guide — Melanotan 2 is not approved for human use. The mechanism is central, not vascular. Erections were driven through melanocortin signaling in the brain and spinal cord rather than through the blood vessels of the penis [3][9][10]. That is what makes this peptide family scientifically distinct from the pills that act on blood flow. ## Tanning, appetite, and the rest of the record Pigmentation is the effect most users seek. Melanotan 2 activates MC1R on melanocytes, raising cAMP (a cellular messenger) and switching on the genes that make eumelanin, the darker pigment — so skin darkens without UV exposure [1][3]. The color can persist for weeks after the peptide clears, because pigment synthesis continues downstream. Appetite suppression shows up consistently in animal work. In male mice, melanotan 2 microinjected directly into the nucleus accumbens (a brain reward region) cut food intake and food-seeking without making the animals sick or changing their metabolic rate [5]. That central appetite effect is the same MC4R pathway that drives the sexual findings. The rest of the record is honest about its limits: no Phase II or Phase III trial has been completed for Melanotan 2 itself, and serious adverse events — renal infarction [4], rhabdomyolysis, priapism, and darkening or eruption of moles — appear in case reports. The full picture, including [Melanotan 2 effects](/effects) people report and the cited safety cautions, leads the effects page. ## How to read this site This is an editorial digest, organized like an instrument readout: each finding is a measured value with its source attached. The [Melanotan 2 research](/research) page covers the mechanism and the key studies. The [what is melanotan 2](/what-is-melanotan-2) page is the plain-language primer. The dosage page reports the doses used in published studies — as research facts, never as instructions. The [melanotan 2 vs pt-141](/vs-pt-141) page compares Melanotan 2 to its better-known derivative. Every quantitative claim links to the [Melanotan 2 references](/references). --- A charcoal instrument-cluster reading of the Melanotan 2 record — the sexual-function trials logged first, the half-life and receptor data stated as plain gauge values, the priapism, kidney and changing-mole case reports flagged in plain sight; no clinic behind the console and nothing here dosed, injected, prescribed, or sold.