What Is Melanotan 2?
Melanotan 2 is a synthetic peptide that mimics alpha-melanocyte-stimulating hormone (α-MSH), a naturally occurring substance secreted from the pituitary gland [1].
The α-MSH peptide, along with all the other peptides in the body, plays an important role in regulating various bodily functions. They produce chemical signals by binding to receptors that are found throughout the body. Specifically, α-MSH binds to a set of receptors called melanocortin receptors [2].
There are 5 types of melanocortin receptors and each has a slightly different effect on the body. MC-1R is responsible for signaling the body to produce more melanin, the substance responsible for darkening skin and hair. Melanotan 2 can bind to the same receptors and may offer similar benefits in test subjects. 
The other melanocortin receptors have different roles. For example, the MC-3R plays a role in regulating appetite and energy and MC-4R plays a role in regulating sexual behavior and erectile function. That's why past studies have linked melanotan 2 to other effects such as heightened libido and decreased body fat levels in test subjects. 
Researchers unfamiliar with melanotan 2 may note that it differs slightly from melanotan 1. We’ll explore the main similarities and differences between these two peptides in the next section. 
 
Melanotan 2 Benefits and Uses
Past studies have linked melanotan II to a number of effects in test subjects. Here's a shortlist of those.
Tanning and skin darkening. Studies have shown that melanotan 2 reduces the chance of test subjects getting sunburn and appears to protect the skin from sun damage. Some studies have suggested that MT-2 can even reduce the chance of getting skin cancer [3, 4, 5].
Reduces hunger. Some research has found that melanotan II plays a role in regulating appetite. In animal studies, It has been found to reduce fat storage and change food preferences away from fatty foods [6, 7, 8].
Regulating blood sugar. Some research has indicated that melanotan 2 doses may play a role in regulating blood sugar [9]. This indicates that further research into the ability of MT-2 to regulate blood sugar levels may be merited. 
Improving impulse control and addictive behavior. Animal studies have found that melanotan 2 doses can help regulate impulsive behavior [10]. This suggests that further research is warranted. 
Increasing libido and improving sexual function. Several studies have linked MT-2 to increased libido in test subjects [11, 12]. In fact, it was originally developed as a way to treat hypoactive sex drives in both male and female research subjects. 
While these purported effects may spike the interest of peptide researchers, it should be stressed that melanotan 2 is a research chemical and has no safe dosage in human test subjects. So, what is known about melanotan 2 side effects? 
Melanotan 2 Side Effects
What side effects does melanotan 2 produce in test subjects? Here’s a shortlist [13]:
Yawning
Stretching
Decreased appetite
Increased sexual arousal and libido
Darkening facial hair
Darkening moles
Flushing
Nausea
Lethargy
Dizziness
Despite these side effects, a review of research on melanotan 2 has concluded that “side effects observed in clinical trials are largely minor” [13]. 
 
Melanotan 2 Dosage | The Verdict?
While melanotan 2 isn’t FDA-approved like melanotan 1, early research indicates that this research chemical has numerous effects on test subjects, suggesting that further research may be warranted. Peptide researchers interested in exploring these effects may consult past clinical studies to see how other researchers have dosed melanotan 2. 
With numerous aspects of melanotan 2 still yet to be explored, qualified researchers may contact Peptide Sciences for more information about ordering this peptide.
References
 
1Plant, T. M. & Zeleznik, A. J. (2014). Knobil and Neill's Physiology of Reproduction: Two-Volume Set. Academic Press. pp. 2230–2231.
2King, S. H., Mayorov, A. V., Balse-Srinivasan, P., Hruby, V. J., Vanderah, T. W., & Wessells, H. (2007). Melanocortin receptors, melanotropic peptides and penile erection. Current topics in medicinal chemistry, 7(11), 1111-1119.
3Brennan, R., Wells, J. G., & Van Hout, M. C. (2014). An unhealthy glow? A review of melanotan use and associated clinical outcomes. Performance Enhancement & Health, 3(2), 78–92.
4Barnetson, R. S., Ooi, T. K., Zhuang, L., Halliday, G. M., Reid, C. M., Walker, P. C., … & Kleinig, M. J. (2006). [Nle4-D-Phe7]-α-melanocyte-stimulating hormone significantly increased pigmentation and decreased UV damage in fair-skinned caucasian volunteers. Journal of Investigative Dermatology, 126(8), 1869-1878.
5FitzGerald, L. M., Fryer, J. L., Dwyer, T., & Humphrey, S. M. (2006). Effect of MELANOTAN®, [Nle4, D-Phe7]-α-MSH, on melanin synthesis in humans with MC1R variant alleles. Peptides, 27(2), 388-394.
6van der Klaauw, A., Keogh, J., Henning, E., Stephenson, C., Trowse, V. M., Fletcher, P., & Farooqi, S. (2015). Role of melanocortin signalling in the preference for dietary macronutrients in human beings. The Lancet, 385, S12.
7Lee, Y. S. (2009). The role of leptin-melanocortin system and human weight regulation: lessons from experiments of nature. Annals Academy of Medicine Singapore, 38(1), 34.
8Bjørbæk, C., & Hollenberg, A. N. (2002). Leptin and melanocortin signaling in the hypothalamus. Vitamins and Hormones, 65, 281-311. https://doi.org/10.1016/S0083-6729(02)65068-X
9Guo, F., Bakal, K., Minokoshi, Y., & Hollenberg, A. N. (2004). Leptin signaling targets the thyrotropin-releasing hormone gene promoter in vivo. Endocrinology, 145(5), 2221-2227.
10York, D. A., Boghossian, S., & Park-York, M. (2011). Melanocortin activity in the amygdala influences alcohol intake. Pharmacology Biochemistry and Behavior, 98(1), 112-119.
11Wessells, H., Fuciarelli, K., Hansen, J., Hadley, M. E., Hruby, V. J., Dorr, R., & Levine, N. (1998). Synthetic melanotropic peptide initiates erections in men with psychogenic erectile dysfunction: double-blind, placebo controlled crossover study. The Journal of Urology, 160(2), 389-393.
12Hakim, L. S. (1998). Synthetic melanotropic peptide initiates erections in men with psychogenic erectile dysfunction: Double-blind placebo controlled crossover study. International Journal of Impotence Research, 10(4), 263-263.
13Brennan, R., Wells, J. G., & Van Hout, M. C. (2014). An unhealthy glow? A review of melanotan use and associated clinical outcomes. Performance Enhancement & Health, 3(2), 78-92.