Kisspeptin: gatekeeper of the reproductive axis

Kisspeptin was first described as a peptide linked to the suppression of cancer metastasis. Within a few years, human genetics revealed its much more fundamental role: without kisspeptin signalling, puberty does not happen. This article covers how kisspeptin controls the reproductive hormonal axis, what studies in people have shown, and where the clinical research stands.

This article summarises published research for scientific understanding. It does not give fertility treatment advice or describe treatment protocols.

From metastasis suppressor to reproductive hormone

The KISS1 gene encodes a precursor protein. In 2001, researchers isolated a 54-amino-acid peptide from human placenta that activated a previously orphan G protein-coupled receptor. They named it metastin because it inhibited the movement and invasion of receptor-bearing cells and reduced metastasis in a mouse melanoma model^[1]. The receptor, first called GPR54, is now known as KISS1R, and the family of peptides as kisspeptins.

What human genetics revealed

The reproductive role emerged from families with isolated hypogonadotropic hypogonadism, a condition in which the brain fails to drive the reproductive axis, so that puberty does not occur.

The pattern is consistent. Loss of kisspeptin or its receptor prevents puberty, and a receptor that signals for too long is associated with puberty that starts too early. These findings are observational, drawn from rare families, but they establish kisspeptin signalling as necessary for normal human reproduction.

How kisspeptin controls the reproductive axis

Reproduction is governed by the hypothalamic–pituitary–gonadal axis. Gonadotrophin-releasing hormone (GnRH) is released in pulses from the hypothalamus and stimulates the pituitary to secrete luteinising hormone (LH) and follicle-stimulating hormone (FSH). These in turn act on the ovaries or testes.

Kisspeptin sits above GnRH. In mice, KISS1R was found on GnRH neurons, and kisspeptin stimulated LH and FSH release in normal mice but had no effect in mice lacking the receptor. In sheep, kisspeptin given into the brain produced a dramatic release of GnRH, with a parallel rise in LH^[6]. The authors called the receptor a "molecular gatekeeper" of the axis.

Kisspeptin neurons in the hypothalamus also produce neurokinin B, and together they regulate the pulsatile release of GnRH^[7]. Kisspeptin is also expressed outside the hypothalamus, including in the placenta and limbic brain regions, which has opened further lines of research^[8].

Human infusion studies

Physiological studies in healthy volunteers established how kisspeptin acts in people.

• Men. In a double-blind, placebo-controlled crossover study of six men, a 90-minute intravenous infusion of kisspeptin-54 increased LH, FSH and testosterone compared with saline. Its plasma half-life was about 28 minutes^[9].
• Women. In healthy women, the LH response to kisspeptin-54 depended strongly on the phase of the menstrual cycle. It was greatest in the preovulatory phase and least in the follicular phase^[10].
• Pulsatility. The shorter kisspeptin-10 potently stimulated LH in men. A continuous low-rate infusion increased LH pulse frequency, consistent with an effect on the GnRH pulse generator^[11].
• Comparison with GnRH. In a direct comparison in healthy men, intravenous GnRH produced gonadotrophin levels about three times those with kisspeptin-10 and about twice those with kisspeptin-54, with only five participants per dose group^[12].

A key limitation emerged early. In women with hypothalamic amenorrhoea, twice-daily kisspeptin injections strongly stimulated LH and FSH on the first day, but the responses had largely disappeared by day 14^[13]. This loss of response, known as tachyphylaxis, shapes how kisspeptin can be studied for repeated use.

Fertility research

The most developed clinical research concerns in vitro fertilisation (IVF). In IVF, a hormonal "trigger" is used to mature eggs before collection, and some triggers carry a risk of ovarian hyperstimulation syndrome (OHSS), a potentially dangerous complication. Because kisspeptin is thought to be the natural driver of the hormone surge that causes ovulation, researchers have investigated whether it could act as a more physiological trigger^[7]. The underlying idea is that stimulating the body's own GnRH and LH release may produce a shorter, more natural hormonal signal than giving a long-acting hormone directly.

• First demonstration. In 53 women undergoing IVF, a single injection of kisspeptin-54 induced egg maturation. Embryo transfer followed in 92% of women, and the clinical pregnancy rate was 23%^[14].
• Women at high risk of OHSS. In a phase 2 randomised trial of 60 women at high risk of OHSS, oocyte maturation occurred in 95%. No woman developed moderate, severe or critical OHSS. The live birth rate per transfer was 45%^[15].

These are encouraging results, but they come from phase 2 studies in a single research programme, without a direct randomised comparison against standard triggers in these reports. The pregnancy rates are not directly comparable across studies with different populations.

Other clinical research

• Intranasal delivery. A randomised, double-blind, placebo-controlled crossover study found that intranasal kisspeptin-54 raised LH in healthy men and women and in women with hypothalamic amenorrhoea, with no side effects reported. Rodent work suggested a route through GnRH neurons in the olfactory system^[16]. The rises in LH were modest in healthy women.
• Diagnosing delayed puberty. In 16 young people with delayed or stalled puberty, the LH response to kisspeptin predicted who would go on to progress through puberty. It outperformed LH responses to GnRH, inhibin B measurement and genetic testing in predicting that outcome^[17]. If confirmed, this could help separate a temporary delay from a lasting condition. It is, however, a single small study that needs replication.
• Brain and behaviour. In 29 healthy men, kisspeptin enhanced limbic brain activity in response to sexual and bonding images^[18]. A randomised trial in women with low sexual desire tested its effects on brain processing of erotic stimuli^[19]. These are imaging studies, not treatment trials.

Limitations and open questions

• Small, concentrated evidence. Most human studies are small physiological experiments or phase 2 trials, and many come from one research centre.
• Tachyphylaxis. Repeated exposure can blunt the response^[13], which limits some potential uses.
• Short half-life. Native kisspeptins are cleared quickly^[9], which complicates sustained use and has motivated work on alternative forms and routes.
• Development status. Kisspeptin was described in 2025 as being developed to treat reproductive disorders^[16]. The peer-reviewed sources reviewed here describe research use rather than an established clinical treatment.
• Beyond reproduction. Potential roles in pregnancy, metabolism, bone and behaviour remain largely at an early research stage^[8].

Summary

Kisspeptin, acting through KISS1R, is essential for human puberty and reproduction. Loss-of-function variants prevent puberty and an activating variant is associated with precocious puberty. It acts upstream of GnRH, and in people it stimulates LH and FSH release in ways that depend on sex, cycle phase and duration of exposure. Clinical research has shown that kisspeptin can trigger egg maturation in IVF, including in women at high risk of OHSS. It has also been explored as a diagnostic probe and delivered intranasally. The evidence is promising but comes mostly from small studies and phase 2 trials, and repeated exposure can blunt the response.