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What Is Kisspeptin? The Reproductive Neuropeptide, Explained
A plain account of the kisspeptin peptide — the KISS1 gene product, its two research forms, its receptor, and the one thing it is not: a supplement.
The short version
Kisspeptin is a small signaling protein the body makes in the brain, encoded by a gene called KISS1. Think of it as the master on-switch for reproduction. The kisspeptin peptide comes in a few lengths — a 54-amino-acid form (kisspeptin-54, originally named metastin) and a shorter 10-amino-acid form (kisspeptin-10) — and they all end in the same chemical tail that lets them lock into one specific docking site, a receptor called KISS1R (older name GPR54).
When kisspeptin docks, it tells a set of brain cells to fire and release GnRH, the hormone that starts the whole reproductive cascade — LH and FSH from the pituitary, then testosterone or ovulation. So kisspeptin is a neuropeptide (a brain-made signaling molecule), not a hormone itself, and definitely not a vitamin or supplement. It is investigational: no version is an approved drug. The rest of this page explains each of those pieces in plain terms.
What is kisspeptin, exactly?
Kisspeptin is the protein product of the KISS1 gene, which sits on human chromosome 1. The body makes a long precursor (145 amino acids) and trims it into shorter active pieces — kisspeptin-54, plus even shorter fragments down to kisspeptin-10. All of them share a conserved C-terminal Arg-Phe-amide (RF-amide) tail, the part the receptor actually grabs. The kisspeptin-10 sequence is Tyr-Asn-Trp-Asn-Ser-Phe-Gly-Leu-Arg-Phe-NH2.
It is made mainly in two clusters of hypothalamic neurons (the arcuate and AVPV nuclei), and also in the placenta and gonads. Its defining job is to be the principal upstream activator of GnRH neurons — which is why it is described as a reproductive neuropeptide and the master regulator of the hypothalamic-pituitary-gonadal axis. The genetics settle its importance: break its receptor and puberty never happens [1].
The receptor, and what binding does
Kisspeptin binds KISS1R (formerly GPR54), a G-protein-coupled receptor on the surface of GnRH neurons. Binding switches on phospholipase C (an enzyme that releases calcium stored inside the cell), which raises intracellular calcium, closes potassium channels, opens cation channels, and depolarizes the neuron so it fires [2]. The downstream consequence is a pulse of GnRH — and then LH and FSH from the pituitary.
Upstream, kisspeptin is made by KNDy neurons (cells co-expressing kisspeptin, neurokinin B and dynorphin), widely regarded as the GnRH pulse generator. This is the engine room: kisspeptin is the relay that converts those neurons' rhythm into the hormone pulses that run reproduction.
Kisspeptin-54, kisspeptin-10 and metastin
The two research forms differ mainly in size and staying power. Kisspeptin-54 is the full-length isoform — the molecule first named metastin when KISS1 was discovered as a cancer metastasis suppressor [13]; in humans it has a plasma half-life around 27 to 28 minutes [8]. Kisspeptin-10 is the short C-terminal fragment, equally able to switch on the receptor but cleared far faster (a functional half-life near 4 minutes). At matched infusion rates in healthy men, the two produce comparable gonadotropin responses [10]. "Metastin" and "kisspeptin-54" now refer to the same molecule — the dual name is a fossil of the dual discovery: a cancer gene that turned out to run reproduction.
Kisspeptin supplement: it is not one
Because "kisspeptin supplement" is a common search, the honest answer deserves a plain statement: kisspeptin is not a dietary supplement, and there is no approved kisspeptin product of any kind. Every human study on record used pharmaceutical-grade peptide given by injection, infusion or nasal spray under medical supervision, in Phase 1/2 research — and no kisspeptin product has been approved by any regulator for any indication [7]. It is a peptide that acts on the body's master reproductive switch, not a nutrient you can take by mouth as a supplement. Material sold as research-grade carries unverified identity, purity and concentration, which is part of why this site treats kisspeptin strictly as an investigational research compound and reports no consumer use.