Kisspeptin is the upstream signal that switches on the whole reproductive axis.

The short version

Kisspeptin is a small protein your body already makes. Its job is to flip the master switch on the system that controls fertility and sex hormones. When kisspeptin lands on its receptor (a docking port on certain brain cells called KISS1R, older name GPR54), those cells release a hormone called GnRH (the brain's go signal for reproduction). GnRH then tells the pituitary gland to send out LH and FSH (the two hormones that run the ovaries and testicles), which in turn raise estrogen or testosterone. So kisspeptin sits one step above GnRH — it is the trigger, not the hormone itself.

Researchers study it for fertility: as a gentler trigger for egg release during IVF, to restart missed periods, and as a marker that runs high in polycystic ovary syndrome (PCOS). It is investigational only — no health agency anywhere has approved it, and it is not a supplement despite what some sellers imply. One quirk matters: push it too hard or too constantly and the response fades within days. What people report, including the downsides, is on the effects page.

What is kisspeptin

Kisspeptin is the product of the KISS1 gene (a stretch of DNA on chromosome 1) and the principal upstream activator of GnRH neurons — the brain cells that pace reproduction ^[1]. The gene's 145-amino-acid precursor is trimmed into a 54-residue form called kisspeptin-54 (its original name was metastin) and shorter pieces including the 10-residue kisspeptin-10. Every active form ends in the same Arg-Phe-amide tail, the part the receptor reads.

Its target is KISS1R (formerly GPR54), a G-protein-coupled receptor (a membrane port that triggers a signal inside the cell). The case for kisspeptin as the master switch is genetic: people who inherit broken copies of GPR54 fail to enter puberty, and mice engineered the same way reproduce that failure, with low LH and FSH ^[1]. Take the switch away and the reproductive axis never turns on. That single finding, published in 2003, reframed a former cancer gene into the keystone of reproductive endocrinology.

Kisspeptin acts upstream of GnRH — it stimulates the body's own GnRH neurons rather than supplying any hormone directly. It is not GnRH, it is not a GnRH-agonist drug, and it is not itself a sex hormone. That distinction runs through everything on this site.

What the human trials have measured

The strongest human evidence is in fertility. In a Phase 2 randomized trial of 60 women at high risk of ovarian hyperstimulation syndrome (OHSS — a dangerous over-response to IVF drugs), a single subcutaneous dose of kisspeptin-54 triggered egg maturation in 95% of women with no case of moderate, severe or critical OHSS; the highest live-birth rate, 62%, followed the 9.6 nmol/kg dose ^[5]. In women whose periods had stopped from hypothalamic suppression, a kisspeptin-54 infusion restored the natural rhythm of LH release, roughly tripling pulse frequency and raising pulse size about six-fold versus placebo ^[4].

In healthy men, an intravenous kisspeptin-10 bolus drove LH from 4.1 to 12.4 IU/L within 30 minutes, and a higher continuous infusion raised testosterone from 16.6 to 24.0 nmol/L ^[3]. Across PCOS cohorts, circulating kisspeptin runs higher than in controls — a meta-analysis of nine studies (n=1,282) found it significantly elevated (standardized mean difference 0.57, 95% CI 0.32-0.82), tracking with LH and testosterone ^[8]. A 2025 study even delivered kisspeptin-54 as a nasal spray and still saw a prompt LH rise, opening a needle-free route ^[6].

Kisspeptin supplement: an honest note on the search term

"Kisspeptin supplement" is a common search, so it is worth being plain: kisspeptin is not a dietary supplement. It is an investigational peptide with no FDA, EMA or other regulatory approval for any use ^[7]. Every human study cited here used pharmaceutical-grade peptide given by trained staff under medical supervision. Material sold outside that setting is an unregulated research chemical with no guarantee of identity, purity or concentration — community reports routinely flag uncertainty over whether a vial is even the form it claims to be. Nothing on this page is a dose, a protocol, or a recommendation to use it.

A signal in a chain, not a hormone you take

The clearest way to hold kisspeptin in mind is as the first station on a relay: kisspeptin to GnRH (in the hypothalamus), GnRH to LH and FSH (from the pituitary), LH and FSH to the sex steroids (from the ovaries or testes) ^[1]. It works by nudging your own neurons, not by replacing any downstream hormone. That is why a single well-timed dose can do so much in the trials — and why the system, like any switch, can be desensitized if it is held down. The mechanism, the trial-by-trial numbers, and the open questions are laid out in Kisspeptin research; the reported effects and the safety reasoning are on Kisspeptin effects.