melanocortin receptor comes up often in conversation and rarely with the context attached. Here we lay out the basics in order, then work through the practical considerations.
Last reviewed on 2026-07-18. Where a claim depends on a specific study, the study is described rather than over-claimed.
Receptor studies place melanotan-2 among non-selective melanocortin agonists, binding MC1R, MC3R, MC4R and MC5R rather than a single subtype. Activation of MC1R on cutaneous melanocytes raises tyrosinase activity and shifts pigment synthesis toward eumelanin, which is darker and more photostable than pheomelanin. Central receptors, particularly MC4R, are associated with appetite suppression and with reported effects on sexual function. Because subtype selectivity is low, the same molecule engages pigment, metabolic and vascular pathways at once, and this breadth is a common explanation offered for the range of adverse events described in user reports.
No regulatory authority has approved melanotan-2 for human use, and several countries classify it as a prescription-only or controlled substance, which restricts lawful supply. Material sold online is generally labelled as a research chemical and is not required to meet pharmaceutical standards of identity or purity. Published human data consist mainly of small uncontrolled studies, case reports and adverse-event notifications, so the evidence base is descriptive rather than confirmatory. Whether repeated melanocyte stimulation alters long-term naevus behaviour remains an open question that no completed trial has resolved.
Melanotan II is a synthetic cyclic heptapeptide with the sequence Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2, corresponding to a molecular formula of C50H69N15O9 and a monoisotopic mass near 1024 daltons. It was designed as a structural analogue of alpha-melanocyte-stimulating hormone, a peptide hormone produced by cleavage of proopiomelanocortin. A lactam bridge between the aspartate and lysine side chains closes the ring, and the C-terminal amide removes a free carboxyl group. Both modifications increase resistance to enzymatic degradation compared with the linear parent hormone. Four substitutions distinguish it from afamelanotide, the linear analogue studied under the name melanotan I.
Receptor-binding studies classify melanotan II as a non-selective melanocortin agonist. It interacts with MC1R, MC3R, MC4R and MC5R, with reported affinities in the low nanomolar range and no strong subtype preference. Activation of MC1R on dermal melanocytes shifts pigment synthesis toward eumelanin, the dark polymer deposited in melanosomes and transferred to keratinocytes. Because the same peptide engages MC4R in the hypothalamus, it also appears in animal work on food intake and erectile response, which is why it is discussed in both pigment and metabolic research. Which receptor populations dominate after systemic exposure in humans is not fully established.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C50H69N15O9 | Free base; salt forms add to total mass |
| Molecular mass | About 1024 daltons | Calculated for the free base |
| Structural class | Cyclic heptapeptide | Contains D-phenylalanine and norleucine |
| Parent hormone | Alpha-melanocyte-stimulating hormone | Endogenous tridecapeptide of 13 residues |
| Receptor profile | Non-selective melanocortin agonist | Interacts with MC1R, MC3R, MC4R and MC5R |
Melanotan-2 is a synthetic linear peptide built from seven amino acids arranged in a short chain. Its sequence is commonly written as Ac-Nle-Asp-His-D-Phe-Arg-Trp-Lys-NH2, which includes a modified N-terminus and an amidated C-terminus. The molecule belongs to the melanocortin family and acts as a receptor agonist. Structural features such as the D-phenylalanine residue and the Nle substitution are associated with increased stability against enzymatic degradation relative to the natural parent peptide.
The compound emerged from research programs in the 1980s that examined analogues of alpha-melanocyte-stimulating hormone for pigmentation and photoprotection. Investigators modified the native sequence to extend activity duration and potency. A related analogue, afamelanotide, was developed within the same broad line of inquiry and eventually gained approval in certain jurisdictions for a rare light-sensitivity condition. Melanotan-2 itself did not progress through the same regulatory route and has no approved therapeutic indication.
Melanocortin receptors comprise five subtypes with distinct tissue distributions and functions. Melanotan-2 is described in the literature as a non-selective agonist that engages several of these subtypes, including MC1R, MC3R, MC4R, and MC5R. MC1R is the subtype most directly linked to melanin production in skin cells. Because the compound is not subtype-selective, its observed effects in experimental settings are generally attributed to activity across multiple receptor pathways rather than to a single target.
Melanotan II is a synthetic peptide analog modeled on alpha-melanocyte-stimulating hormone, a naturally occurring signaling peptide involved in pigmentation. Its structure is a cyclic heptapeptide containing two non-natural substitutions, norleucine at position four and D-phenylalanine at position seven. These modifications resist enzymatic breakdown and extend the molecule's activity relative to the native hormone. The compound binds melanocortin receptors and is studied mainly as a pharmacological tool rather than a therapeutic product. It has never received approval as a medicine in any major jurisdiction.
The compound was developed in the late 1980s and 1990s by academic researchers investigating photoprotection. The rationale held that stimulating melanin production might reduce ultraviolet damage to skin and lower skin cancer risk. Early work examined receptor binding, pigment response, and short-term tolerability in small studies. That program did not produce an approved drug, and formal development stalled after early-phase trials. Whether induced pigmentation confers meaningful photoprotection remains an open question.
Melanotan-2 is a synthetic cyclic heptapeptide designed as an analogue of alpha-melanocyte-stimulating hormone, the naturally occurring peptide involved in pigmentation signalling. Its sequence is conventionally written as Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2, with a lactam bridge joining the aspartate side chain to the lysine side chain. The empirical formula is C50H69N15O9 and the monoisotopic mass lies near 1023.5 daltons. N-terminal acetylation and the D-configured phenylalanine both increase resistance to enzymatic breakdown compared with the parent hormone.
Pharmacologically, melanotan-2 behaves as a non-selective agonist across the melanocortin receptor family. Binding at MC1R on dermal melanocytes promotes eumelanin synthesis, which underlies the tanning response described in early human work. Activity at the centrally expressed MC4R receptor is associated with reported effects on appetite and erectile function. Because the peptide does not discriminate strongly among receptor subtypes, attributing any single observed effect to one receptor pathway is generally not possible without selective antagonists or receptor knockout models.
Zooarchaeology by mass spectrometry, commonly referred to by the abbreviation ZooMS, is a scientific method that identifies animal species by means of characteristic peptide sequences in the protein collagen. ZooMS is the most common archaeological application of peptide mass fingerprinting (PMF) and can be used for species identification of bones, teeth, skin and antler. It is commonly used to identify objects that cannot be identified morphologically. In an archaeological context this usually means that the object is too fragmented or that it has been shaped into an artefact. Archaeologists use these species identification to study among others past environments, diet and raw material selection for the production of tools.
== Diagnosis == The disease may be diagnosed based on a clinical examination, which identifies signs and symptoms generally associated with the people who have the condition. Genetic testing for known pathological variants is preferred, by testing of the COL6A1, COL6A2, COL6A3 and COL12A1 genes. In the case of a VUS, testing of dermal fibroblast culture is used for an accurate diagnosis. Additional laboratory tests may be performed before genetic testing, such as creatine kinase (CK) blood test, MRI of the muscles, and electromyography (EMG). Phenotypes of overlap between Ullrich congenital muscular dystrophy (UCMD) and Bethlem can be assumed. In the differential diagnosis of UCMD, even in patients without finger contractures, Bethlem myopathy could be considered.
==== Structural problems ==== Structurally, changes within the musculature in the intestine, such as increased elastin, can lead to increased frequency of herniation. Laxity of the phreno-esophageal and gastro-hepatic ligaments can lead to hiatal hernia, which in turn can lead to commonly reported symptoms such as acid reflux, abdominal pain, early satiety, and bloating. Internal organ prolapses and intestinal intussusceptions occur with greater frequency in patients with weakened connective tissues.
Sources: en.wikipedia.org
== Interactions == Being metabolized only to a small extent, the substance has a low potential for interactions. In studies, inhibitors of the liver enzymes CYP3A4, CYP2C19, and CYP2C9, as well as the CYP3A4 inducer rifampicin, had no relevant influence on baricitinib concentrations in the bloodstream. While baricitinib blocks a number of transporter proteins in vitro, clinically relevant interactions via this mechanism are considered very unlikely, except perhaps for the cation transporter SLC22A1 (OCT1). An additive effect with other immunosuppressants cannot be excluded.
In the brain, the canonical mechanism of CB1 receptor activation is a form of short-term synaptic plasticity initiated via retrograde signaling of endogenous CB1 agonists such as 2AG or AEA (two primary endocannabinoids). This mechanism of action is called depolarization-induced suppression of inhibition (DSI) or depolarization-induced suppression of excitation (DSE), depending on the classification of the presynaptic neuron acted upon by the retrograde messenger (see diagram at left). In the case of CB1R agonism on the presynaptic membrane of a GABAergic interneuron, activation leads to a net effect of increased activity, while the same activity on a glutamatergic neuron leads to the opposite net effect. The release of other neurotransmitters is also modulated in this way, particularly dopamine, dynorphin, oxytocin, and vasopressin.
Bempedoic acid is a prodrug. It is activated to the thioester with coenzyme A by the enzyme acyl-CoA synthetase in the liver. The activated substance inhibits ATP citrate lyase, which is involved in the liver's biosynthesis of cholesterol upstream of HMG-CoA reductase, the enzyme that is blocked by statins. The substance also activates AMP-activated protein kinase, but this effect is likely not relevant in humans.
Sources: en.wikipedia.org
No regulatory agency has authorised melanotan-2 as a medicine for any indication. It circulates mainly as a research chemical or through unregulated channels. As a result, identity, purity and content are not independently guaranteed.
Melanotan-1, also called afamelanotide, is a linear analogue with greater selectivity for MC1R and has received approval in some jurisdictions for a specific photosensitivity disorder. Melanotan-2 is cyclic, less selective, and reaches central receptors more readily. The two are often confused in online discussion despite different pharmacology and regulatory status.
Alpha-MSH is an endogenous tridecapeptide derived from pro-opiomelanocortin. Melanotan-2 reproduces its core receptor-binding sequence inside a shortened, stabilised ring. The result is a molecule with a longer effective half-life and higher potency than the parent hormone.
No. It is a synthetic analogue carrying four amino acid changes, a lactam ring and an amidated C-terminus. The natural hormone is a linear thirteen-amino-acid peptide processed from proopiomelanocortin.