The short version of melanocortin receptor fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2025-11-30. Anything still debated is marked as such rather than presented as settled.
Melanotan II binds several melanocortin receptor subtypes rather than a single target. MC1R on melanocytes drives melanin synthesis, while MC3R and MC4R participate in energy balance, appetite, and sexual response pathways. This lack of selectivity explains why reported effects extend beyond skin darkening. Substitutions at positions four and seven, including norleucine and D-phenylalanine, increase potency and resistance to peptidases. Understanding which receptor mediates which effect remains an active area of investigation.
Published human data come mostly from small, short studies rather than large controlled trials. Reported outcomes include increased skin pigmentation and, in some reports, effects on appetite and libido, but sample sizes are small and follow-up is limited. Whether long-term use produces durable pigment changes or adverse effects is not established. Because products sold outside pharmacies are not standardized, the actual content of any given vial is often unknown. Independent testing of such material is uncommon.
Structurally, Melanotan-2 retains the core recognition motif of alpha-melanocyte-stimulating hormone while adding a lactam bridge that links two side chains and constrains the molecule into a ring. This modification lowers susceptibility to enzymatic degradation. The compound acts as an agonist at melanocortin receptors, particularly subtypes associated with melanin production. Because the same receptor family influences several physiological processes, researchers note that its activity is not confined to pigmentation alone. Receptor selectivity continues to be examined in published studies.
Melanotan-2 is a synthetic cyclic heptapeptide designed as an analogue of alpha-melanocyte-stimulating hormone, a naturally occurring peptide involved in pigmentation signalling. Its sequence incorporates modified residues that increase potency and extend biological activity relative to the native hormone. The compound binds receptors of the melanocortin family and is examined mainly in laboratory research. It does not occur naturally and exists only as a manufactured chemical entity produced by solid-phase synthesis.
The peptide was developed during the 1980s by researchers investigating melanocortin signalling and skin pigmentation pathways. Early work focused on analogues of alpha-melanocyte-stimulating hormone that would resist enzymatic breakdown more effectively than the parent molecule. Melanotan-2 emerged from that programme as a shortened, cyclised variant. Reports describing its synthesis and receptor activity later appeared in the scientific literature. Commercial availability grew through unregulated channels rather than through pharmaceutical approval.
| Property | Value | Notes |
|---|---|---|
| Chemical class | Synthetic cyclic heptapeptide | Analog of alpha-melanocyte-stimulating hormone |
| Primary receptor family | Melanocortin receptors MC1R through MC5R | Binding is not subtype-selective |
| Development period | 1980s | Synthesized during pigmentation and appetite research |
| Regulatory status | Not an approved medicine | No major regulator has authorized human use |
| Related compound | Afamelanotide | Linear analog studied for photoprotection |
Note: Other substances once thought to be vitamins were given B-numbers, but were disqualified once discovered to be either manufactured by the body or not essential for life. See § Related compounds for numbers 4, 8, 10, 11, and others.
=== Acoustic lysis === This method uses ultrasonic waves to generate areas of high and low pressure which causes cavitation and in turn, cell lysis. Though this method usually comes out clean, it fails to be cost effective and consistent.
=== Cell integrity loss === Cell integrity loss is caused by bacteria releasing dissolved algicidal compounds, which are toxic to algae, into the surrounding water, causing rapid cell lysis of algae cells. Cell lysis occurs when algicidal enzymes or small molecules degrade cell walls and membranes, causing structural collapse. While most compounds released by algicidal bacteria cause cell lysis by damaging the algae cells walls, other lysis inducing mechanisms can include ion permeability disruption, and acidification of the cytoplasm by small molecules passing through the cell wall. An example of a bacterium which causes cell integrity loss is a strain of Alteromonas abrolhosensis, named JY‑JZ1, which when cultured, showed strong algicidal activity. Through microscopy, researchers found that algal cells exposed to this bacterium had damaged cell membranes and leaked intracellular contents which indicates cell death by lysis.
13 March – Five people are taken to hospital for treatment after a bus crashes into a high rise block of flats in Paisley, Glasgow. 14 March – The Scottish Parliament Corporate Body finds Michael Matheson in breach of the Ministerial Code over his £11,000 iPad bill. Mountaineer Anna Wells becomes the first woman to reach the top of all of Scotland's 282 Munros in one winter season. 15 March – Following trial and conviction at the High Court in Glasgow, double murderer Peter Duffy is sentenced to at least 30 years in prison for the murder of his wife, Emma Baillie, and brother, John-Paul Duffy, in separate incidents in Coatbridge in 2022. 17 March – HMP Kilmarnock becomes the first privately run prison in Scotland to pass into the ownership of the Scottish Prison Service after its contract with Serco comes to an end. 19 March – Scottish Prison Service director Allister Purdie gives evidence to the Scottish COVID-19 Inquiry, and apologises to the family of Callum Inglis, who died at Addiewell Prison during the pandemic, after his family learned of the death through word of mouth before they were told formally by prison authorities. 21 March – The Scottish Parliamentary Corporate Body confirms that members of Scottish Parliament staff will no longer be allowed to wear rainbow lanyards, or any other badge or jewellery associated with social issues, while at Holyrood. The Wildlife Management and Muirburn (Scotland) Bill passes its final vote in the Scottish Parliament.
=== Breast cancer === Anastrozole is used in the treatment and prevention of breast cancer in women. The Arimidex, Tamoxifen, Alone or in Combination (ATAC) trial was of localized breast cancer and women received either anastrozole, the selective estrogen receptor modulator tamoxifen, or both for five years, followed by five years of follow-up. After more than 5 years the group that received anastrozole had better results than the tamoxifen group. The trial suggested that anastrozole is the preferred medical therapy for postmenopausal women with localized estrogen receptor-positive breast cancer.
Sources: en.wikipedia.org
The human dilemma is hardly new. We find ourselves through no wish of our own on this slowly revolving planet in an obscure corner of a vast universe. Our questioning intelligence will not let us live in cow-like content with our lot. We have a deep need to know why we are here. What is the world made of? More important, what are we made of? In the past religion answered these questions, often in considerable detail. Now we know that almost all these answers are highly likely to be nonsense, having sprung from man's ignorance and his enormous capacity for self-deception ... The simple fables of the religions of the world have come to seem like tales told to children. Even understood symbolically they are often perverse, if not rather unpleasant ... Humanists, then, live in a mysterious, exciting and intellectually expanding world, which, once glimpsed, makes the old worlds of the religions seem fake-cosy and stale Crick was especially critical of Christianity:
Apart from user contributed missions it is also possible to play co-operatively through the original Half-Life game and its expansions, though the expansions can only be accessed if owned by everyone in the server. Team Fortress Classic – Originally a mod ported from Quakeworld that introduced a class-system style of play that allowed for many diverse playing styles. With the introduction of Steam it became a standalone game and as of October 10, 2007 it has a commercially released sequel Team Fortress 2. Trinity Command – Similar to Unreal Tournament's Domination game mode where two teams try to control various points on the map. GameStar said the included bots are useful but noted the maps as monotonous and classes unbalanced. Turbo – A racing game where players control snarks, beetle-like creatures from Half-Life. PC Zone gave it a rating two out of five, calling the mod great fun but noted the lack of players online and its tendency to crash. Underworld: Bloodline – an asymmetric multiplayer FPS based on the Underworld film franchise. Developed by Black Widow Games in 2003 as a promotional tie-in for the film Underworld, it is the only officially licensed Half-Life mod associated with a Hollywood movie. The mod was available on the Sony Pictures official website until the end of 2007. Players choose between Vampires and Lycans, engaging in objective-based combat across urban maps. Each faction has distinct classes, weapons, and movement abilities.
==== Metabolism and elimination ==== When taken orally, about 95% of a dose of estradiol is metabolized in the intestines and liver into estrone and estrogen conjugates such as estrone sulfate, estrone glucuronide, and estradiol sulfate, among others, prior to entering the circulation. As a result, circulating estrone and estrogen conjugate levels are markedly elevated, in a highly unphysiological manner, with oral estradiol. Whereas the ratio of circulating estradiol to estrone is about 1:1 in premenopausal women and with transdermal estradiol, oral estradiol produces a ratio of about 1:5 on average and as high as 1:20 in some women. In addition, whereas levels of estradiol with menopausal replacement dosages of oral estradiol are in the range of the follicular phase of the normal menstrual cycle, levels of estrone resemble those during the first trimester of pregnancy. Moreover, whereas normal physiological estrone sulfate levels are 10 to 25 times higher than those of estradiol and estrone in premenopausal women, levels of estrone sulfate with oral estradiol are an additional 8 to 20 times higher than normal premenopausal or postmenopausal estrone sulfate levels. One study found that estrone sulfate levels were 200-fold higher than estradiol levels with 2 mg/day oral micronized estradiol or oral estradiol valerate, and estrone sulfate levels can reach up to nearly 1,000-fold higher concentrations than estradiol in some cases.
== Function == Androgens that bind to and activate the androgen receptor have numerous physiological functions which can broadly divided into androgenic (male sexual development) and anabolic (building muscle and bone). The anabolic effects are important in both males and females, although females have lower circulating levels of androgens. The physiologically most important androgens are testosterone (T) and dihydrotestosterone (DHT), which are considered classical androgens because their role in human health was discovered in 1930s. However, much later, in 2010s, the role in human health of 11-oxygenated androgens was established, namely, of 11-ketotestosterone (11KT) and 11-ketodihydrotestosterone (11KDHT), that both bind and activate the human androgen receptor with affinities, potencies, and efficacies that are similar to that of testosterone (T) and DHT, respectively, although 11-oxygenated androgens were long known to be principal androgens in teleost fishes. The main biochemical route to T and DHT is the canonical (classical) pathway that proceeds from pregnenolone (P5). Alternatively, DHT but not T can be produced through a backdoor pathway that proceeds from 17α-hydroxyprogesterone (17OHP) or progesterone (P4). The function of androgen backdoor pathways is to produce physiologically significant androgens in normal conditions where the conventional pathway is insufficient, such as in male early sexual differentiation. Sexual differentiation is a process by which hormones determine anatomic phenotype, mainly the development of the reproductive organs.
Sources: en.wikipedia.org
No regulator in a major market has approved it for human use. It appears in research settings and in products marketed outside pharmacy channels. Legal status for personal possession varies by country.
Afamelanotide is a linear analog that has received approval in some jurisdictions for a specific photoprotection indication. Melanotan II is cyclic and less selective across melanocortin receptors. The two are related but are not interchangeable in regulatory or clinical terms.
A compound that activates several receptor subtypes may produce effects beyond pigmentation. Selectivity influences which tissues respond and shapes the side-effect profile described in reports. Designing subtype-selective analogs is a stated goal of melanocortin research.
It is a synthetic cyclic heptapeptide and an analogue of alpha-melanocyte-stimulating hormone. The molecule is produced by chemical synthesis rather than extracted from a biological source.