| Class | Nonapeptide hormone |
| Molecular weight (Da) | 1007.2 |
| Half-life (indicative) | ~1–6 min |
| Research status | Approved drug |
Research context (RUO): PT-141, kisspeptin and oxytocin are three neuro-endocrine peptides that in research touch on arousal, the reproductive axis and social bonding. All three are supplied solely for in-vitro laboratory research and are not intended for human or animal use.
PT-141, kisspeptin and oxytocin: three neuro-endocrine peptides
PT-141, kisspeptin and oxytocin are often mentioned in the same breath because all three touch on behaviour and reproduction via the nervous and hormonal system (neuro-endocrine). Yet they act at very different points. This page is an overview (hub): for each peptide we briefly explain what the research focuses on and link to the separate pillar. All findings come from studies, not from use by the reader.
PT-141 (bremelanotide) — arousal via the brain
PT-141 is a melanocortin agonist that stands out in research because it does not act via the blood vessels, but via the central nervous system. It is studied around sexual arousal and the role of the MC4 receptor in motivation and reward circuits in the brain.
Kisspeptin — the switch of the reproductive axis
Kisspeptin (kisspeptin-10) sits higher up the chain: it is a signalling peptide that activates the reproductive axis by stimulating the release of GnRH, which then drives the hormones LH and FSH. In research it is therefore seen as a central “switch” of the reproductive hormone axis.
Oxytocin — social bonding
Oxytocin — colloquially the “cuddle hormone” — is studied mainly around social bonding, trust and the processing of social signals in the brain. It is both a hormone and a neuromodulator, which makes it a broad research subject.
How they relate to each other
In short, the three act at different levels: kisspeptin high in the hormone chain (reproductive axis), PT-141 on arousal via the brain, and oxytocin on social behaviour and bonding. They are studied together because each illuminates a piece of the neuro-endocrine regulation of behaviour and reproduction.
What the clinical research with bremelanotide showed
Under the name bremelanotide, PT-141 has come furthest of the three. The agent was approved in the United States in 2019 for premenopausal women with acquired, generalised HSDD. The registered dose is 1.75 milligrams subcutaneously, at least three quarters of an hour beforehand and at most once per day. The pharmacokinetic profile is strikingly sharp: peak concentration is reached after about an hour, the terminal half-life is around 2.7 hours and bioavailability with subcutaneous administration approaches one hundred percent. The side effect profile is well documented too, with nausea in about forty percent of participants, flushing in one in five and headache in just over one in ten. PT-141 shares its point of action with the melanocortin agonists from the melanotan-2 research, but with a clearly different receptor preference.
What the clinical research with kisspeptin shows
In human studies kisspeptin is given intravenously, usually as kisspeptin-54. In a double-blind crossover study from 2023 in 32 men with reduced sexual desire, an infusion of 1 nanomole per kilogram per hour over 75 minutes altered activity in brain regions involved in processing sexual stimuli, and the physiological response at the end of the task was more than half higher than under placebo. Kisspeptin therefore sits one level higher in the chain than PT-141: it drives the release of GnRH and with it the entire hypothalamic-pituitary axis, rather than a melanocortin receptor directly.
| Feature | PT-141 | Kisspeptin | Oxytocin |
|---|---|---|---|
| Point of action | Melanocortin receptor | KISS1R, above GnRH | Oxytocin receptor |
| Length | 7 amino acids | 54 or 10 amino acids | 9 amino acids |
| Clinical status | Approved in the US, 2019 | Research stage | Registered, different indication |
| Route in studies | Subcutaneous | Intravenous infusion | Intravenous or intranasal |
Why oxytocin is the trickiest of the three
Oxytocin is a nonapeptide with a half-life of a few minutes in blood, which means the route of administration largely determines the research. Intranasal administration is the usual route in behavioural studies, but how much of the substance actually reaches the central nervous system is still disputed, and the plasma levels measured say little about the concentration at the site of action. On top of that, oxytocin effects are strongly context dependent: the same dose gives different outcomes in different social set-ups. Replication is accordingly the biggest bottleneck in this subfield, and that is a reason to read oxytocin results more cautiously than those of the other two.
How the three relate to one another in a study design
Anyone wanting to place the three in one framework is best off ordering them by the level at which they intervene. Kisspeptin works upstream, on the control of the gonadal axis. PT-141 works centrally but outside that axis, via melanocortin receptors in the brain. Oxytocin works on the social and contextual layer around it. They are therefore not alternatives to each other but three different entry points into the same subject. A study design that judges all three on the same outcome measure shortchanges at least two of them; a sensible comparison picks per substance an outcome measure that matches the level of intervention.
Quality & purity
Every relevant batch is independently HPLC-tested by an external laboratory; the CoA is publicly verifiable per batch. See also why we rejected a batch.
Frequently asked questions
What do PT-141, kisspeptin and oxytocin have in common?
All three are neuro-endocrine peptides that touch on behaviour and reproduction in research, but via different mechanisms and at different levels.
What does PT-141 act on?
On the melanocortin receptors in the central nervous system (mainly MC4), and it is studied around sexual arousal — unlike vasodilating substances that act peripherally.
What does kisspeptin do?
It stimulates the release of GnRH and thereby activates the reproductive axis (LH/FSH). Researchers see it as a central switch of that axis.
Why is oxytocin called the cuddle hormone?
Because of research that associates it with social bonding and touch. That is a popular term; the actual research shows a more nuanced picture.
May I use these peptides?
No. All three are intended solely for in-vitro laboratory research (RUO), not for human or animal use.
Read more & research at Peplife
- PT-141 (bremelanotide) research
- Kisspeptin-10 research
- Oxytocin research
- View all related peptides
- Melanotan 2 vs PT-141
Sources: Thurston et al., MC4R agonism & sexual brain processing, J Clin Invest (2022) · Meyer-Lindenberg et al., oxytocin as a social neuropeptide, Nat Rev Neurosci
Research Use Only. All products are supplied exclusively for in vitro laboratory research. Not intended for diagnostic or therapeutic use in humans or animals, and not approved by the EMA or FDA.
PT-141, kisspeptin and oxytocin HPLC-tested by an external laboratory, CoA per batch verifiable and discreet EU shipping.