Alpha-MSH

Native 13-amino-acid melanocortin hormone cleaved from proopiomelanocortin that activates MC1R, MC3R, MC4R, and MC5R, driving pigmentation, appetite suppression, and anti-inflammatory signaling; it is the parent molecule of melanotan I, melanotan II, and KPV.

Also referenced as: α-MSH, Alpha-melanocyte-stimulating hormone, α-melanocyte-stimulating hormone, Alpha-melanotropin, α-melanotropin

Also appears in: Dermal

What is Alpha-MSH?

Alpha-MSH (α-melanocyte-stimulating hormone) is the native human melanocortin hormone: a 13-amino-acid peptide, Ac-Ser-Tyr-Ser-Met-Glu-His-Phe-Arg-Trp-Gly-Lys-Pro-Val-NH2, produced by enzymatic cleavage of proopiomelanocortin (POMC) followed by N-terminal acetylation and C-terminal amidation. Its sequence is identical to the first 13 residues of ACTH, which is why the two hormones share the His-Phe-Arg-Trp core that all melanocortin receptors recognize. In humans it is made by POMC neurons of the hypothalamic arcuate nucleus, by the pituitary, and locally in skin keratinocytes and melanocytes and in immune cells.

It appears on the research-peptide market mainly as the “original” molecule behind a family of better-known products. Every widely traded melanocortin peptide is a modification of it: melanotan I is [Nle4, D-Phe7]-α-MSH, the linear analog approved as afamelanotide; melanotan II is a cyclic seven-residue lactam built around the same core motif; and KPV is simply α-MSH(11-13), the unmodified C-terminal tripeptide. PeptideBenchmark profiles each of those separately, and they are not interchangeable with the native hormone described here.

The distinction matters more than it usually does with parent-and-analog pairs, because the analogs exist specifically to fix a property the native hormone lacks — resistance to enzymatic degradation. A vendor listing that treats α-MSH as a generic substitute for melanotan is describing a molecule with materially different pharmacokinetics.

How it works

• MC1R agonism in pigment cells. α-MSH binds MC1R on melanocytes, a Gs-coupled receptor whose activation raises cAMP, activates PKA and CREB, and upregulates MITF and the melanogenic enzymes tyrosinase, TYRP1, and DCT — shifting melanin synthesis toward eumelanin. MC1R is described as the most important positive regulator of mammalian melanogenesis (Slominski et al., Physiological Reviews, 2004;84(4):1155-1228).
• A calcium-dependent binding pocket shared with the drugs. Cryo-EM structures of the MC1R–Gs complex bound to α-MSH, to afamelanotide, and to the synthetic agonist SHU9119 show all three occupying the same orthosteric pocket around the conserved HFRW motif, with a calcium ion playing a crucial role in ligand binding (Ma et al., Cell Research, 2021;31(10):1061-1071). This is the structural reason the analogs behave like the native hormone at the receptor while differing in stability.
• Central MC3R/MC4R signaling in energy balance. α-MSH released from arcuate POMC neurons acts at MC3R and MC4R across the hypothalamus and brainstem as an appetite suppressant that also increases energy expenditure, opposed at the same receptors by AgRP (Cone, Nature Neuroscience, 2005;8(5):571-578). This pathway — not the pigmentation one — is the target of the approved MC4R agonist setmelanotide.
• Anti-inflammatory signaling, partly independent of pigmentation. α-MSH inhibits NF-κB activation induced by a range of inflammatory stimuli, including TNF and lipopolysaccharide (Manna & Aggarwal, Journal of Immunology, 1998;161(6):2873-2880), and the melanocortin system as a whole is a well-characterized endogenous brake on inflammation (Catania et al., Pharmacological Reviews, 2004;56(1):1-29). The C-terminal KPV fragment retains part of this activity without meaningful melanocortin-receptor agonism (Hiltz & Lipton, FASEB Journal, 1989;3(11):2282-2284).
• Photoprotection beyond melanin. In cultured human melanocytes, α-MSH activated antiapoptotic pathways and reduced UV-induced DNA damage (Kadekaro et al., Cancer Research, 2005;65(10):4292-4299), and separately suppressed oxidative stress through a p53-mediated pathway (Kadekaro et al., Molecular Cancer Research, 2012;10(6):778-786) — effects distinguishable from simply making more pigment.
• Short-lived by design. The native peptide is rapidly cleaved by serum and tissue proteases. The entire stabilized-analog field traces to a single observation: substituting norleucine at position 4 and D-phenylalanine at position 7 produced a melanotropin 26 times as potent as α-MSH in the adenylate cyclase assay, resistant to degradation by serum enzymes, with prolonged activity (Sawyer et al., PNAS, 1980;77(10):5754-5758). That compound became afamelanotide.

Research status

The hormone is thoroughly characterized; the drug is not. α-MSH has a very large basic-science literature and essentially no controlled human efficacy record of its own. No regulator has approved a drug product containing native α-MSH for any indication.

Historical human work. Injected α- and β-MSH were shown to darken human skin more than sixty years ago (Lerner & McGuire, Nature, 1961;189:176-179). That observation is the foundation of the whole melanocortin tanning literature, but it predates modern trial design, receptor pharmacology, and dose-response methodology.

Registered trials of the native peptide. ClinicalTrials.gov lists two interventional studies that actually administer α-MSH itself, and neither has reported. NCT00004496 was a University of Texas Phase 1 study of intravenous α-MSH in patients on chronic hemodialysis, transplant recipients at risk, and patients with established ischemic acute renal failure, sized to find a maximum tolerated dose; it ran from 1999 to 2003, completed with an estimated 45 participants, and posted no results. NCT06293664 is a small double-blind randomized crossover study at the Dasman Diabetes Institute testing a pharmaceutical-grade α-MSH infusion against saline on the glucose and insulin area-under-the-curve response to an oral glucose tolerance test in type 2 diabetes, with an estimated enrollment of 13 participants; it is not phase-designated, and no results have been posted. A separate listing, NCT03451578, uses α-MSH only as a measured analyte in ocular disease, not as an intervention — and reported being unable to obtain measurable levels in the samples collected.

The strongest recent human data is a preprint. A cross-species study reported that peripheral administration of α-MSH in healthy human volunteers was well tolerated and reduced glucose and insulin incremental AUC during an oral glucose tolerance test by 39% and 35% respectively, attributing the effect to an MC5R-dependent skeletal-muscle glucose-uptake pathway supported by non-human primate, myotube, and MC5R-deficient mouse work (Swan et al., bioRxiv, 2025, doi:10.1101/2025.03.26.645414). As of this writing it has not appeared in a peer-reviewed journal, and it should be read as a preprint result, not as an established finding.

Where the analogs succeeded. Three α-MSH–derived melanocortin drugs are FDA approved, and none of them is α-MSH: afamelanotide (SCENESSE, October 8, 2019), an MC1R agonist indicated to increase pain-free light exposure in adults with a history of phototoxic reactions from erythropoietic protoporphyria; bremelanotide (VYLEESI, 2019) for hypoactive sexual desire disorder in premenopausal women; and setmelanotide (IMCIVREE, November 2020) for obesity from POMC, PCSK1, or LEPR deficiency, an indication since broadened to Bardet-Biedl syndrome and younger patients. In vitiligo, afamelanotide implants combined with narrowband UV-B produced faster and more complete repigmentation than narrowband UV-B alone in a randomized multicenter trial of 55 patients (Lim et al., JAMA Dermatology, 2015;151(1):42-50).

Where an α-MSH analog failed. ABT-719 — a synthetic α-MSH analog carrying six N-terminal lysines, formerly AP214, acquired by Abbott from Action Pharma in 2012 and carried forward by AbbVie — reached a randomized, double-blind, placebo-controlled Phase 2b trial in 240 patients undergoing high-risk on-pump cardiac surgery (NCT01777165). Despite strong preclinical protection against ischemic and septic acute kidney injury, it did not lower AKI incidence by AKIN criteria, did not move novel injury biomarkers, and did not change 90-day outcomes (McCullough et al., Journal of the American Heart Association, 2016;5(8):e003549). It is the largest controlled human test of the melanocortin system’s anti-inflammatory, organ-protective promise — the mechanism most often invoked for α-MSH on the research market — and it was negative. The melanocortin analogs that did win approval succeeded on pigmentation, sexual desire, and appetite instead.

Open questions in oncology. α-MSH signaling has been reported both as protective against UV-driven melanocyte damage and as a factor in melanoma biology, and a 2023 review concluded its role in melanoma prevention and treatment remains debated and controversial rather than settled in either direction (Dall’Olmo et al., Journal of Translational Medicine, 2023;21(1):562). Radiolabeled α-MSH analogs are also under investigation as melanoma-targeting agents, which is a diagnostic and delivery application rather than a hormone-replacement one.

Common dosage forms

Research suppliers list α-MSH almost entirely as lyophilized powder in sealed vials, commonly in the 5 mg to 10 mg range, typically as the trifluoroacetate salt, intended for reconstitution and labeled for laboratory use. Cold-chain storage is standard because the peptide is labile.

Secondary presentations that circulate include pre-mixed nasal-spray bottles and spray kits, topical or cosmetic solutions positioned around pigmentation, and multi-vial “tanning” kits that pair α-MSH with melanotan analogs. Because the parent hormone and its analogs are frequently packaged and marketed together, the specific compound in a kit is not always evident from the outer labeling.

α-MSH also exists as a clinical laboratory analyte — reference laboratories run plasma α-MSH immunoassays — which is a measurement, not a product format. This section describes formats only and is not dosing guidance.

Key considerations

• Regulatory status. Native α-MSH is an endogenous human hormone with no drug approval in any jurisdiction. The approved melanocortin medicines are all analogs (afamelanotide, bremelanotide, setmelanotide), and approval of an analog confers nothing on the parent peptide. Products sold under α-MSH or melanotan naming are not equivalent to a prescribed melanocortin drug.
• The pharmacokinetic gap is the whole story. Native α-MSH is rapidly degraded by proteases, which is precisely why [Nle4, D-Phe7] substitution was made in 1980 and why every commercially successful melanocortin peptide since has been a stabilized analog. It is also not orally bioavailable. Any claim that the native hormone matches an analog’s duration of effect is contradicted by the reason the analog was created.
• Evidence gap. There is no completed, peer-reviewed, controlled efficacy trial of native α-MSH for any indication. Both registered interventional studies are small and unreported — a Phase 1 safety study that completed in 2003 without posting results, and a 13-participant crossover study that is not phase-designated — while the most substantial human dataset is an unrefereed preprint. Mechanistic depth in this compound should not be mistaken for clinical evidence.
• Non-selective agonism and class safety signals. α-MSH activates MC1R, MC3R, MC4R, and MC5R without meaningful selectivity, so effects on pigment, appetite, sexual function, cardiovascular tone, and exocrine glands cannot be separated by dosing. Nausea, flushing, and darkening of existing moles are documented class effects of potent melanocortin agonists, and the relationship between melanocortin signaling and melanoma remains an open question rather than a closed one. Independent verification of identity and content in reconstituted or blended presentations is difficult.
• Naming confusions are unusually dense here. α-MSH is distinct from melanotan I, from melanotan II (a cyclic heptapeptide analog), and from KPV (α-MSH residues 11-13). Bare “MSH” is ambiguous across α-, β-, and γ-MSH, which have different receptor preferences. Development codes compound the problem: NDP-MSH, NDP-α-MSH, [Nle4, D-Phe7]-α-MSH, CUV1647, melanotan I, and afamelanotide are all one molecule, PT-141/bremelanotide descends from melanotan II rather than from the native hormone, and the code ABT-719 was reused — Abbott had already applied it to an unrelated 1990s antibacterial 2-pyridone — so literature searches on melanocortin development codes return substantial off-target material.
• “Low MSH” testing sits outside mainstream medicine. Plasma α-MSH measurement features prominently in chronic inflammatory response syndrome (CIRS) and mold-biotoxin frameworks, where depressed MSH is treated as a core marker. CIRS is not an established diagnosis in mainstream medicine, the assays used are not broadly standardized across laboratories, and α-MSH’s lability in a collected specimen makes results sensitive to handling. A reported “low MSH” value is not a validated indication for supplementing the hormone.