Melanocortins and others

This family activates a set of receptors called melanocortin (muh-LAN-oh-kor-tin) receptors, of which there are five types spread around the body. Because they are spread out, these compounds tend to do several things at once, which is the theme of the whole group.

Melanotan II (MEL-uh-no-tan) is the original. It triggers melanocortin receptors broadly. Its headline effect is pigmentation, the production of melanin that tans your skin, which is why it became popular as a tanning compound. Because it is not selective, it also nudges other receptors, so people report effects on appetite and libido alongside the tan.

PT-141, also called bremelanotide (brem-eh-LAN-oh-tide), was built from Melanotan II but engineered to be more selective. It mostly targets the receptors tied to sexual arousal and skips the tanning side, so it is used specifically for libido in both men and women. It is the more refined, more targeted version of the same starting point.

A fair warning on Melanotan II in particular: broad receptor activation means broad effects, including nausea and changes to moles and freckles, so it is one to research carefully rather than treat casually.

A few peptides do not fit any of these buckets and are not worth a full lesson yet. DSIP (delta sleep-inducing peptide) is one, used by some people for sleep. If you run into a name that is not in this course, that is usually a sign it is niche, very new, or both. Treat it as unproven until you see real evidence.