Alpha-MSH (Alpha-Melanocyte-Stimulating Hormone), Research Reference
Alpha-MSH (alpha-melanocyte-stimulating hormone, or α-MSH) is an endogenous 13-amino acid neuropeptide with the sequence Ac-Ser-Tyr-Ser-Met-Glu-His-Phe-Arg-Trp-Gly-Lys-Pro-Val-NH2. It is derived from the precursor protein POMC (pro-opiomelanocortin) through post-translational cleavage by prohormone convertases, primarily in the pituitary intermediate lobe, hypothalamic neurons, and keratinocytes of the skin. POMC also gives rise to ACTH, beta-endorphin, and other biologically active peptides, making it one of the most pharmacologically productive precursor proteins in neuroendocrinology.
Alpha-MSH is distinct from the synthetic melanocortin research compounds used more widely in the peptide research community. PT-141 (Bremelanotide) and Melanotan II are structurally modified synthetic analogues that achieve greater potency, receptor selectivity, and plasma stability compared to the endogenous peptide. Alpha-MSH itself is primarily of research interest as an endogenous signalling molecule, with its synthetic analogues carrying more established research community protocols.
Quick Reference
| Parameter | Reported Value |
|---|---|
| Full name | Alpha-melanocyte-stimulating hormone (α-MSH) |
| Sequence | Ac-Ser-Tyr-Ser-Met-Glu-His-Phe-Arg-Trp-Gly-Lys-Pro-Val-NH2 |
| Precursor | POMC (pro-opiomelanocortin) |
| Length | 13 amino acids |
| Molecular weight | ~1665 Da |
| Half-life | ~1–2 hours (plasma, endogenous) |
| Primary receptors | MC1R, MC3R, MC4R |
| Research dose ranges | Studied at mcg ranges in human research; no established community protocol |
| Administration routes | Intranasal, subcutaneous (research contexts) |
Overview
Alpha-MSH occupies a central position in the melanocortin signalling system, a network of receptors and endogenous ligands that governs pigmentation, inflammation, energy homeostasis, and sexual function. The melanocortin system involves five receptor subtypes (MC1R through MC5R), each with distinct tissue distribution and functional roles. Alpha-MSH, as the primary endogenous agonist across these receptors, represents the parent molecule from which all synthetic melanocortin peptides are derived or adapted.
Research has investigated Alpha-MSH and its fragments across several biological domains:
- Skin pigmentation and photoprotection: Alpha-MSH is the principal endogenous stimulator of melanogenesis. MC1R activation on melanocytes drives the enzymatic pathway that produces eumelanin (dark, photoprotective pigment) from tyrosine. UV radiation-induced Alpha-MSH release by keratinocytes is an endogenous photoprotective response, triggering skin darkening as a consequence of sun exposure. MC1R variants in human populations are strongly associated with skin phototype, red hair, and increased UV sensitivity.
- Inflammation and immune modulation: Research has characterised broad anti-inflammatory properties of Alpha-MSH operating through MC1R and MC3R expressed on macrophages, monocytes, neutrophils, and dendritic cells. MC1R activation suppresses NF-kB signalling and reduces production of pro-inflammatory cytokines including TNF-alpha, IL-1beta, and IL-6. Research has investigated this pathway in models of arthritis, inflammatory bowel disease, sepsis, and neuroinflammation.
- Appetite suppression and energy homeostasis: MC4R in the hypothalamus and brainstem is a critical node in the leptin-melanocortin energy balance pathway. Leptin secreted by adipose tissue drives hypothalamic POMC-expressing neurons to release Alpha-MSH, which then activates MC4R to suppress appetite and increase energy expenditure. Loss-of-function mutations in MC4R are the most common monogenic cause of severe human obesity, highlighting the physiological significance of this pathway.
- Neuroprotection: Research has investigated Alpha-MSH for neuroprotective properties in models of ischaemia, traumatic brain injury, and neurodegenerative disease, attributed to anti-inflammatory signalling in microglial cells and direct neuronal MC4R activation. Intranasal delivery has been investigated as a route for CNS access, bypassing the blood-brain barrier to some extent via olfactory nerve pathways.
- Sexual function: MC4R activation in the CNS is implicated in sexual arousal pathways in both male and female research models. This pathway underlies the sexual function research interest in Melanotan II and PT-141, both of which activate MC4R. Alpha-MSH’s role in this pathway is physiological but its clinical translation in this context has been pursued through the synthetic analogues rather than the endogenous peptide.
Research Dose Ranges
Alpha-MSH does not have an established research community protocol in the way that synthetic melanocortin analogues (PT-141, Melanotan II) do. Clinical and translational research studies have administered Alpha-MSH at mcg-range doses, typically intravenously or intranasally. Human research studies investigating Alpha-MSH for inflammation, neuroprotection, and fever reduction have reported intranasal doses in the 10 mcg to 50 mcg range per administration. These are research study parameters, not community protocols.
The absence of a community dosing protocol for Alpha-MSH reflects its pharmacokinetic limitations as an endogenous peptide: rapid enzymatic degradation, a short plasma half-life, and lack of the structural modifications that give PT-141 and Melanotan II their more favourable research profiles.
Reported Effects in Research
The following represent research findings from published literature. These are not community anecdotal reports.
Anti-inflammatory Effects
Research has investigated Alpha-MSH for its anti-inflammatory properties across multiple model systems. Studies in rodent models of acute inflammation and endotoxaemia reported suppression of IL-1beta and TNF-alpha following systemic Alpha-MSH administration. Clinical pilot research in humans investigated intranasal Alpha-MSH for its potential role in modulating fever and systemic inflammation responses. Research groups including those of Anna Catania have published on C-terminal tripeptide fragments of Alpha-MSH (including KPV) as anti-inflammatory agents with potential clinical utility.
Skin Pigmentation
Alpha-MSH remains the gold standard endogenous stimulus for melanogenesis research. Research using Alpha-MSH has characterised the MC1R signalling pathway in detail, including the downstream production of cAMP, activation of tyrosinase, and synthesis of eumelanin versus phaeomelanin. Genetic studies correlating MC1R variants with Alpha-MSH responsiveness have contributed substantially to understanding of skin phototype and melanoma risk.
Appetite and Energy Homeostasis
Research in MC4R knockout animals and human MC4R loss-of-function mutations has established the appetite-regulatory axis in which Alpha-MSH is a critical signal. Research has also investigated whether exogenous Alpha-MSH or analogues can reduce food intake and increase energy expenditure in animal models of obesity, providing the mechanistic basis for the interest in MC4R agonism as a metabolic target.
Reported Side Effects
Alpha-MSH is an endogenous peptide, and research studies using exogenous administration have generally noted a tolerability profile consistent with its physiological role. Reported effects in research include:
| Effect | Context |
|---|---|
| Nausea | Reported in some human research studies at higher doses |
| Skin darkening | Expected consequence of MC1R activation; common with repeated systemic administration |
| Blood pressure changes | Reported in some acute administration studies; attributed to MC3R/MC4R vascular effects |
| Penile erection | Reported in male subjects at doses activating MC4R; same mechanism as synthetic analogues |
The synthetic melanocortin analogues (PT-141, Melanotan II) carry their own reported side effect profiles that are more thoroughly characterised due to more extensive community use.
Storage and Handling
Alpha-MSH as a research compound follows standard lyophilised peptide handling guidelines.
Lyophilised Powder
- Refrigerator (2–8 degrees C): Preferred storage; stable for 12 months or more
- Freezer: Acceptable for longer storage; avoid repeated freeze-thaw cycles
- Light sensitivity: Protect from light, particularly given the Met residue at position 4
Reconstituted Solution
- Refrigerator: Use within 2–4 weeks of reconstitution
- Standard diluent: Bacteriostatic water or sterile water
- Discard if the solution becomes cloudy or discoloured
Frequently Asked Questions
What is the difference between Alpha-MSH and PT-141 or Melanotan II? Alpha-MSH is an endogenous 13-amino acid peptide produced naturally in the pituitary and skin. PT-141 and Melanotan II are synthetic, structurally modified analogues developed to achieve greater potency, receptor selectivity, and resistance to enzymatic degradation. Melanotan II is a cyclic non-selective melanocortin agonist with strong MC1R and MC4R activity. PT-141 was developed specifically to isolate MC4R agonism. Alpha-MSH itself has a plasma half-life of roughly 1 to 2 hours and lacks the modifications that make synthetic analogues suitable for community research protocols.
What receptors does Alpha-MSH act on? Alpha-MSH binds to all five melanocortin receptors (MC1R through MC5R) but its primary research-characterised actions occur at MC1R (pigmentation, anti-inflammatory on immune cells), MC3R (energy homeostasis, anti-inflammatory), and MC4R (appetite suppression, energy expenditure, sexual function). The physiological pleiotropism of Alpha-MSH across these receptor subtypes reflects its role as a broad endogenous regulator of pigmentation, inflammation, and metabolic state.
Is Alpha-MSH used in the research peptide community the same way as BPC-157 or Ipamorelin? No. Alpha-MSH is an endogenous neuropeptide rather than a synthetic research compound with an established community dosing protocol. The research community more commonly uses synthetic melanocortin analogues including Melanotan II and PT-141. Alpha-MSH appears in basic science and translational research literature but does not have a community protocol with commonly reported dose ranges. Smaller fragments such as KPV have seen more characterised community use for anti-inflammatory applications.
What research has investigated Alpha-MSH for inflammation? Alpha-MSH has been investigated for anti-inflammatory properties since the 1990s. Research published by groups including that of Anna Catania investigated systemic and intranasal Alpha-MSH for models of inflammation, fever, and neuroinflammation. The anti-inflammatory mechanism operates through MC1R and MC3R on macrophages, monocytes, and dendritic cells, suppressing NF-kB activation and downstream cytokine production. Intranasal delivery has been investigated as a non-invasive route for CNS access.
Related Pages
Goals: Skin, Hair & Cosmetic · Fat Loss and Recomposition
Class: Melanocortin Peptides
Also see: PT-141 (Bremelanotide) · Melanotan II · KPV
References and Further Reading
- Catania A, et al. (2004). The melanocortin system in control of inflammation. Scientific World Journal, 4, 317–330. PubMed
- Cone RD. (2005). Anatomy and regulation of the central melanocortin system. Nature Neuroscience, 8(5), 571–578. PubMed
- Farooqi IS, et al. (2003). Clinical spectrum of obesity and mutations in the melanocortin 4 receptor gene. New England Journal of Medicine, 348(12), 1085–1095. PubMed
- Brzoska T, et al. (2008). Alpha-melanocyte-stimulating hormone and related tripeptides: biochemistry, antiinflammatory and protective effects in vitro and in vivo, and future perspectives for the treatment of immune-mediated inflammatory diseases. Endocrine Reviews, 29(5), 581–602. PubMed
- Lim CT, et al. (2017). Melanocortin peptides as MC3R/MC4R agonists for obesity pharmacotherapy. British Journal of Pharmacology, 174(8), 718–728. PubMed