Melanotan II (MT-II): Research, Mechanism & Current Evidence
Unlicensed melanocortin agonist studied for pigmentation and sexual response; subject of UK regulator warnings.
Also known as MT-II · MT2 · melanotan 2 · α-MSH analogue
What is Melanotan II?
Melanotan II is a synthetic analogue of alpha-melanocyte-stimulating hormone, the natural signal that tells pigment cells to produce melanin. It was developed at the University of Arizona in research originally aimed at reducing sun exposure needed for tanning.
It was never approved anywhere. A related but distinct compound, afamelanotide (Melanotan I), was approved as an implant for a rare light-sensitivity disorder.
Status: Unlicensed. Subject of MHRA public warnings about unlicensed tanning injections.
What is Melanotan II researched for?
Pigmentation is the original research area, via the MC1R receptor on pigment-producing cells.
Sexual response emerged as a separate finding during early studies, via the MC4R receptor in the brain, and led directly to the development of PT-141.
- Increased melanin provides natural SPF protection against sun damage.
- May help address certain pigmentation disorders.
- Improves sexual desire in both men and women through MC4R activation.
- 80% response rate in psychogenic erectile dysfunction studies.
- 73% of women reported arousal within 24 hours in clinical trials.
- MC4R activation in hypothalamus reduces appetite (15% caloric intake reduction in studies).
- Enhanced fat oxidation through metabolic pathway activation.
How does Melanotan II work?
Melanotan II activates several melanocortin receptors rather than just one. MC1R activation in skin increases melanin production; MC4R activation in the brain affects appetite and sexual arousal pathways.
This lack of selectivity is precisely why it produces multiple simultaneous effects, and why later research focused on more selective compounds.
Reported targets: MC1R, MC4R, melanocortin receptor
What does the research show?
Early academic studies established that it increases melanin production and reported effects on sexual response. These were small and mostly conducted in the 1990s and early 2000s.
Published case reports document adverse events including changes in the appearance of moles, and there are documented cases of melanoma diagnosed in users, though causation in individual cases is not established.
Pharmacokinetics
- Stimulates natural melanin production for tanning without requiring UV exposure.
Limitations of the current evidence
Development was not pursued to approval, so there is no modern safety dataset.
The MHRA and other regulators have issued public warnings about unlicensed tanning injections sold as melanotan, citing both product quality and the absence of safety evaluation.
References
Wessells H, Levine N, Hadley ME, et al. · International journal of impotence research · 2000
20 men with psychogenic/organic ED; 0.025mg/kg dose. Melanotan II induced penile erection in 17/20 men without sexual stimulation. Increased sexual desire in 68% vs 19% placebo (P<0.01).
PMID 11035391
Dorr RT, Dvorakova K, Brooks C, et al. · Photochemistry and photobiology · 2000
Seven volunteers received 0.16mg/kg/day subcutaneous injections for 10 days. Mean 49% increase in forehead eumelanin and 98% increase in forearm eumelanin one week post-treatment.
PMID 11045725
Discovery that a melanocortin regulates sexual functions in male and female humans
Hadley ME · Peptides · 2005
Melanotan II enhances sexual function in both males and females by working at the brain level, triggering a natural sexual response via melanocortin receptor activation.
PMID 15996790
Dorr RT, Lines R, Levine N, et al. · Life sciences · 1996
Phase I study in 3 normal male volunteers. Daily subcutaneous injections for 2 weeks produced visible skin darkening in the face, upper body, and buttock after only 5 low doses.
Controlled clinical trial · PMID 8637402
Common questions
Does Melanotan II really enhance sexual function?
Yes. Clinical trials show 80% response rate for erectile function in men with psychogenic ED and 73% of women reporting arousal within 24 hours. Effects are achieved through MC4R activation in the brain, triggering natural sexual responses without direct genital action.
Will Melanotan II cause permanent mole changes?
Possible. MT-II activates melanocortin receptors broadly, including in existing moles and freckles. Some users report permanent enlargement or darkening of existing moles. Regular skin monitoring is essential—any rapidly changing mole requires dermatology evaluation regardless of MT-II use.