# Melanotan 2 Research: Studies, Mechanism, and What They Found > Melanotan 2 research, summarized: the pigmentation pilot study, the erectile-dysfunction trial, the rodent appetite and brain data, and the recent safety reports — all cited. Two small human trials, a wall of rodent work, and a sobering case-report record — organized and cited. ## Before the details Here's the **Melanotan 2** evidence base in plain terms. Two small, controlled human studies form the backbone: one on tanning, one on erections. Everything else about effects on the body — appetite, fat, the brain, nerve repair — comes from animals, mostly rats and mice. And a separate, important pile of evidence is case reports: doctors writing up individual patients who were harmed. So the picture is uneven. The pigment and erection effects are backed by real (if tiny) human trials. The appetite and brain effects are well-shown in animals but not confirmed in proper human trials. The harms are documented case by case rather than counted in a big study. Below, each major finding gets its own section, with the exact species, dose, and outcome — and a note that doses are study facts, never instructions, because Melanotan 2 is not approved for people. ## Pigmentation: the first human signal — Melanotan 2 tanning The founding result. In a single-blind, alternating-day, placebo-controlled pilot Phase I study, three healthy men received subcutaneous Melanotan 2 escalated from 0.01 to 0.025-0.03 mg/kg every other weekday for two weeks. After only five low doses, 2 of 3 men showed measurable darkening of the face, upper body, and buttocks — with no UV exposure. The same men reported spontaneous erections (1-5 hours) and mild nausea, and somnolence limited the top 0.03 mg/kg dose [4]. The mechanism behind that tan: switching on MC1R raises cyclic AMP inside pigment cells, driving the cascade that upregulates tyrosinase and pushes melanin synthesis toward dark eumelanin [2]. Preformulation work characterized Melanotan 2 explicitly as a peptide being evaluated to prevent sunlight-induced skin cancers, and measured its physical properties, including a low oral bioavailability of 4.6% in the rat — which is why every real-world use is by injection [43]. ## Sexual function: the accidental discovery The tanning study's erection "side effect" became its own line of research. In a double-blind, placebo-controlled crossover study, 10 men with psychogenic erectile dysfunction received 0.025 mg/kg subcutaneous Melanotan 2 or placebo. Eight of 10 developed clinically apparent erections; mean duration of greater-than-80% tip rigidity was 38.0 minutes with the peptide versus 3.0 minutes with placebo (p=0.0045), with transient nausea, stretching, and yawning that needed no treatment [5]. This is a central effect, not a vascular one. Reviews of centrally acting erectile-dysfunction agents list the alpha-MSH agonist Melanotan 2 among CNS drugs that shift autonomic balance toward erection — while cautioning that the mechanism comes mainly from rodent work and human extrapolation stays speculative [44]. In rats, intravenous Melanotan 2 activates oxytocin neurons in the hypothalamus (Fos expression in the supraoptic and paraventricular nuclei), a circuit thought to underlie both the sexual and the autonomic responses [45]. ## Appetite, fat, and the brain (rodent data) In male C57BL/6J mice, microinjecting Melanotan 2 straight into the nucleus accumbens (a brain reward hub) at 0.1-1 nmol per side significantly cut food intake in both home-cage and lever-pressing tests, and reduced the effort animals would put in to get food — without causing taste aversion or changing metabolic rate [6]. That's a clean separation of "less hungry" from "feels sick," at least in mice. This maps onto the human appetite reports, but stays animal-only evidence. The receptor logic is solid: MC4R in the hypothalamus governs appetite and energy balance, MC3R handles energy homeostasis and thermogenesis [1]. None of this has been tested in a controlled human weight study with Melanotan 2. ## Recent safety reports and the bigger context The newest published work is, tellingly, about harm and misuse. A 2026 case report documents reversible oral-mucosal pigmentation in a man who self-injected Melanotan 2 (400 ug every other day for 64 days; 12.8 mg total): brown pigment appeared on the gums of both jaws and on the cheek lining, with the cheek pigment fading by 28 days after stopping while gum pigment persisted at reduced intensity at 3 months [46]. It is one of the most recent MT-2 safety reports. The endogenous-ligand context comes from a 2023 review of alpha-MSH biology, which lays out the melanocortin system, the MC1R melanin pathway, and melanocortin signaling's relevance to melanoma — the backdrop against which synthetic analogs like Melanotan 2 act [47]. For the deeper molecular story, see the [melanotan 2 mechanism of action](/mechanism-of-action) page; for the cited harms in plain English, see [Melanotan 2 effects](/effects). --- Bright, plain-English digests of the Melanotan 2 literature — the science and the risks, never a sales pitch or a prescription.