Melanocortin Peptides

Acts on melanocortin receptors

Mechanism

Melanocortin peptides act on the melanocortin receptor system (MC1R through MC5R), a family of receptors distributed throughout the body that regulate skin pigmentation, sexual function, appetite, inflammation, and energy metabolism. Melanotan I (afamelanotide, FDA-approved as Scenesse for EPP) and Melanotan II are the most well-known, primarily used for tanning. PT-141 (bremelanotide) targets MC4R specifically for sexual function and is FDA-approved as Vyleesi.

The breadth of the melanocortin system means these peptides often produce multiple effects simultaneously. Melanotan II causes tanning, appetite suppression, and increased sexual arousal because it activates multiple receptor subtypes. More targeted compounds like PT-141 and afamelanotide were developed to isolate specific effects by focusing on individual receptor subtypes.

This page collects every melanocortin peptide on PeptideWiki. Browse individual profiles for receptor selectivity, dosing, and safety data.

Peptides (3)

PT-141 (Bremelanotide)

Sexual Health & Libido

PT-141 (Bremelanotide) is a hormone receptor activator that works directly in the brain, unlike blood flow-based medications for sexual dysfunction. It is FDA-approved as Vyleesi for treating hypoactive sexual desire disorder (HSDD) in premenopausal women.

KPV

Immune & Inflammation

KPV is a naturally occurring three-amino-acid peptide derived from alpha-MSH, a hormone involved in inflammation control. Research focuses on its strong anti-inflammatory properties, particularly in inflammatory bowel disease and skin conditions.

ACTH (Cosyntropin)

Hormones & Endocrine (Non-GH)

Cosyntropin is a synthetic version of the first 24 building blocks of the body's natural stress hormone ACTH. It is used as an FDA-approved diagnostic tool (Cortrosyn) to test whether the adrenal glands are working properly, and is also used to treat certain conditions like infantile spasms.

Frequently Asked Questions

Melanotan II activates MC1R receptors on melanocytes (pigment-producing skin cells), stimulating the production of eumelanin (brown/black pigment). This increases the skin's baseline pigmentation independent of UV exposure. Some UV exposure accelerates and deepens the tan, but Melanotan II can produce visible darkening without any sun at all. The pigmentation develops gradually over 1-2 weeks of use and fades slowly after discontinuation as melanin turns over with normal skin cell replacement.

Melanotan II is not FDA-approved and carries notable side effects. Common effects include nausea, facial flushing, and fatigue after injection. More concerning is its effect on moles: it can darken existing moles, potentially making melanoma screening more difficult. There are reports of new moles appearing during use. Anyone with a personal or family history of melanoma should avoid it. Regular dermatological screening is recommended for users. The lack of long-term safety data means the risk profile is not fully characterized.

Melanotan I (afamelanotide) is more selective for MC1R (the pigmentation receptor) and has minimal effects on sexual function, appetite, or other melanocortin pathways. It was developed specifically as a tanning agent and is FDA-approved for erythropoietic protoporphyria (a condition where sunlight causes severe pain). Melanotan II is less selective and activates MC1R, MC3R, MC4R, and MC5R, which is why it produces tanning plus appetite suppression, sexual arousal, and other effects. For tanning alone with fewer side effects, Melanotan I is the more targeted option.

PT-141 (bremelanotide) was actually discovered during Melanotan II research when subjects reported sexual arousal as a side effect. It was developed as a more selective melanocortin agonist targeting MC4R in the hypothalamus, which mediates sexual desire and arousal. It produces minimal tanning compared to Melanotan II because it has lower affinity for MC1R. PT-141 became the first FDA-approved melanocortin drug for sexual dysfunction (approved as Vyleesi for hypoactive sexual desire disorder in women).

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