Kisspeptin Spray 5 mg

One-Peptides KISSPEPTIN 5 mg — Kisspeptin-10 nasal spray for laboratory research

KISSPEPTIN 5 mg nasal spray is a research reagent (Research Use Only) supplied as a pre-dissolved solution. Kisspeptin is not registered as a medicine or a dietary supplement in the European Union (EMA) or in other major jurisdictions (FDA). It is a synthetic decapeptide intended solely for laboratory research into KISS1R receptor signalling and the physiology of the reproductive axis. It is not a medicine, a supplement, or a product for human use. Kisspeptin acts on the HPG hormonal axis — a sensitive area (fertility, sex hormones). The entire description concerns physiology and the findings of scientific research; it does not and cannot contain any claims of “increasing testosterone”, “improving libido”, or “affecting potency” in humans.

Kisspeptin is among the most extensively clinically studied peptides of the reproductive axis — and, at the same time, one of those around which the greatest number of oversimplifications has accumulated. For decades, the hypothalamic gonadotrophin-releasing hormone (GnRH) was regarded as the summit of the reproductive hormonal hierarchy. The discovery of kisspeptin’s role pushed that boundary one storey higher: kisspeptin proved to be the signal that decides when GnRH neurons should “fire”. It has been called the “switch” of the reproductive axis, because without proper kisspeptin signalling the entire hormonal cascade remains silent.

In the One Peptides catalogue, kisspeptin functions as a RUO chemical reagent in a pre-dissolved nasal spray format. This format simplifies laboratory work on intranasal administration: the solution requires no reconstitution of a lyophilisate, and the dosing system allows reproducible sampling of the peptide under controlled conditions. It is a technical solution for teams working with the HPG axis in research models — not a form intended for administration to humans.

Kisspeptin-10 (KP-10) is a synthetic decapeptide — the ten-amino-acid C-terminal fragment of the parent kisspeptin molecule, an agonist of the KISS1R receptor (formerly GPR54). It acts as the master regulator of the hypothalamic–pituitary–gonadal (HPG) axis: it stimulates GnRH neurons, which trigger the secretion of the gonadotrophins LH and FSH, and the gonadotrophins then act on the gonads. In laboratory supply it is available solely as a research reagent (RUO).

What kisspeptin is — sequence and class

Kisspeptin is a family of peptides derived from a precursor protein encoded by the KISS1 gene. From the precursor — preprokisspeptin, comprising 145 amino acids — proteolytic processing produces several active fragments of differing length: kisspeptin-54, kisspeptin-14, kisspeptin-13, and kisspeptin-10 (KP-10). All of these forms share a common, biologically active C-terminus, and all bind to the same receptor.

Kisspeptin-10 is the shortest form retaining full biological activity — it is precisely the shared C-terminal motif that is responsible for binding and activating the receptor. For this reason, KP-10 has become a popular tool in research on kisspeptin signalling: a short sequence, simpler synthesis, and receptor activity comparable to that of the longer variants.

The receptor for kisspeptin is KISS1R, previously known as GPR54 — a G protein-coupled receptor (GPCR), initially an “orphan” whose ligand was identified only later. Its activation triggers an intracellular cascade leading to the stimulation of GnRH-secreting neurons. KISS1R is located primarily on GnRH neurons in the hypothalamus. Naturally, kisspeptin occurs in both sexes and plays a fundamental role in sexual maturation and reproduction — as confirmed by the discovery that inactivating mutations of the receptor are associated in humans with an absence of spontaneous puberty.

Chemical characterisation

The hypothalamic–pituitary–gonadal (HPG) axis

To understand why kisspeptin is described as a “higher-order regulator”, it is worth tracing how the entire reproductive axis works. The hypothalamic–pituitary–gonadal (HPG) axis is a hierarchical hormonal system in which the signal flows downwards from the brain to the gonads, and the products of the gonads return as a feedback signal. The simplest way to picture it is as a control system with a central rhythm regulator.

The cascade can be described step by step:

• KNDy neurons in the hypothalamus. The arcuate nucleus of the hypothalamus contains a population of neurons named with the abbreviation KNDy — after three substances that co-occur within them: Kisspeptin, Neurokinin B, and Dynorphin. It is here that the pulsatile rhythm governing the entire axis is generated. KNDy neurons release kisspeptin.
• Stimulation of GnRH neurons. Kisspeptin acts on the KISS1R receptors on GnRH neurons, stimulating them to release gonadotrophin-releasing hormone (GnRH) in pulses. Without this signal, GnRH neurons remain largely inactive — which is why kisspeptin is called the “switch”.
• The pituitary and the gonadotrophins. GnRH travels via the portal circulation to the anterior lobe of the pituitary, where it stimulates the secretion of two gonadotrophic hormones: luteinising hormone (LH) and follicle-stimulating hormone (FSH).
• The gonads and sex hormones. LH and FSH act on the gonads. In men, LH stimulates the Leydig cells in the testes to produce testosterone, while FSH supports spermatogenesis. In women, the gonadotrophins regulate the maturation of ovarian follicles, ovulation, and the production of oestrogens and progesterone.
• Feedback. The sex hormones return as a feedback signal, modulating the activity of the higher levels of the axis, including the KNDy neurons themselves.

GnRH here is the executor relaying the command to the pituitary, but it is kisspeptin that sets the rhythm and decides when the command is to be sent. This is precisely why research on kisspeptin is so significant for understanding reproductive physiology — by modulating the highest level of the axis, the response of the entire downstream cascade can be observed.

Mechanism of action in research

Kisspeptin exerts its action through agonism of the KISS1R (GPR54) receptor on GnRH neurons. Binding of the peptide to the receptor triggers an intracellular signalling cascade (the Gq protein/PLC pathway), which leads to depolarisation and stimulation of GnRH neurons to release the hormone in pulses. In other words, kisspeptin does not replace GnRH — it “switches it on”.

The best-documented effect observed in studies involving humans is the influence of kisspeptin administration on the secretion of LH (and, to a lesser extent, FSH). In studies with healthy volunteers, administration of the peptide was associated with an increase in blood gonadotrophin concentrations, confirming kisspeptin’s role as a direct stimulator of the axis above the level of GnRH. The hormonal mechanism here is therefore indirect: kisspeptin acts on a neuronal receptor, not on the gonads or on sex hormone receptors. The studies analysed the influence on the entire reproductive axis — from the central signal to the gonadotrophic response.

The reference data on the mechanism come from in vitro receptor studies, animal models, and controlled physiological studies involving humans conducted at academic centres.

The nasal spray format — research context

Here, full honesty regarding the routes of administration is required. Most published clinical studies on kisspeptin in humans used injectable administration — intravenous (IV) or subcutaneous (SC) — because these allow tight control of exposure within the paradigm of studying axis physiology. The clinical data described in the literature therefore come mainly from these routes.

The nasal spray format makes the same reagent available as a pre-dissolved solution intended for research into intranasal administration. Intranasal administration is of research interest for peptides on account of the richly vascularised nasal mucosa, but in the case of kisspeptin we do not have the same clinical database as for injection. It should be regarded as a format for exploratory research into this route of administration, not as a pathway with an established profile in humans. The solution requires no reconstitution — it is ready for laboratory work in accordance with the experimental plan.

What the research says

Kisspeptin is among the few reproductive-axis peptides to have been the subject of an extensive programme of controlled studies involving humans — chiefly at academic centres, within the paradigm of studying physiology rather than registering a medicine. The review below is purely scientific in nature: it describes what was observed, and does not suggest any application whatsoever.

The reproductive axis and gonadotrophin secretion. In studies involving healthy volunteers, kisspeptin administration was associated with an increase in the secretion of LH (and, to a lesser extent, FSH), confirming its role as a stimulator of the axis above the level of GnRH. These were primarily observations of an acute, short-term hormonal response.

Arousal and stimulus processing. The team of Alexander Comninos and Waljit Dhillo at Imperial College London conducted research on the influence of kisspeptin not only on hormones but also on the central processing of stimuli associated with sexual arousal. In brain-imaging studies (fMRI), modulation of the activity of structures involved in the processing of emotions and stimuli of a sexual nature was observed relative to placebo. This line of work opened a discussion of kisspeptin’s role at the interface of the hormonal system and the central regulation of behaviour — as a subject of research into the mechanism, not as an application.

Hypothalamic amenorrhoea and fertility. The group of Channa Jayasena and colleagues studied kisspeptin in the context of disorders of the reproductive axis in women, including hypothalamic amenorrhoea — a condition in which the HPG axis is “silenced” despite normal gonadal structure. The capacity of the peptide to stimulate the axis in situations of its hypofunction was investigated, as was its potential significance in the field of diagnostics and assisted reproduction.

The assisted-reproduction (IVF) context. One of the most frequently described directions was the role of kisspeptin as a trigger inducing oocyte maturation in in vitro fertilisation protocols. Because kisspeptin acts “upstream” of the axis and leads to an endogenous LH surge, it was analysed as an alternative to the classical methods of triggering ovulation, with the prospect of a more favourable profile in selected patient groups.

The interpretative framework remains unambiguous: these are physiological studies in small groups, conducted under controlled conditions, assessing mainly the acute response of the axis to administration of the peptide. They are not registration studies, nor material justifying use outside the laboratory.

Kisspeptin versus PT-141

Kisspeptin and PT-141 (bremelanotide) are sometimes set side by side as “libido peptides”, which is misleading — they share an area of research interest, but their mechanism differs. They are two distinct signalling systems.

Kisspeptin acts hormonally, via the HPG axis. Its receptor is KISS1R/GPR54, and its biological effect is realised through the cascade GnRH → LH/FSH → sex hormones. The kisspeptin signal modifies the working of the entire reproductive hormonal system.

PT-141 acts centrally, via the melanocortin system. Bremelanotide is an agonist of melanocortin receptors, chiefly MC4R in the hypothalamus and brainstem. It does not pass through the HPG axis and does not alter the gonadotrophin profile — it modulates the signal in the central nervous system independently of the reproductive hormonal system.

In short: kisspeptin is a reproductive-axis peptide (hormonal, KISS1R receptor), PT-141 is a melanocortin peptide (central, MC4R receptor). A shared area of research interest does not mean a shared mechanism.

One Peptides quality specification

Each batch of kisspeptin nasal spray undergoes a full analytical control process.

• HPLC ≥98% — the area of the main peak is ≥98% of the sum of areas (liquid chromatography with UV detection).
• MS confirmation — confirmation of the peptide’s identity by mass spectrometry.
• COA per batch — a certificate of analysis for each batch (theoretical/measured mass, HPLC profile, date of synthesis, batch number).
• Cold chain 2–8°C — a monitored cold chain from synthesis to delivery.
• Batch traceability — the batch number in three places: label, invoice, and COA.

The reagent is intended solely for laboratory applications — without any therapeutic claims and without any intended administration to humans. The preparation of working solutions should be carried out in accordance with the experimental plan and the procedures adopted in the laboratory.

Safety and limitations

All of the information below comes from academic clinical studies on the physiology of the reproductive axis and does not constitute a recommendation for the use of kisspeptin in humans in the European Union, where the peptide is not registered as a medicine.

In published studies involving volunteers, kisspeptin administered within a short window, under controlled conditions, was generally well tolerated — the authors reported a favourable profile in acute exposure, with no signals of serious events at the concentrations used in the experiments. This observation, however, applies strictly to research conditions: medical supervision, single or short-term administrations, and selected groups of participants.

What the literature does not settle:

• No data on long-term exposure — the studies focused on the acute and short-term response of the axis. The profile under chronic administration remains uncharacterised.
• No validation of the intranasal format — the clinical database concerns mainly injectable administration (IV/SC); the intranasal route remains an exploratory area.
• No validation in the general population — the study participants were selected groups in clinical settings; there is no basis for extrapolating the conclusions beyond the laboratory.
• Unknown consequences of chronic modulation of the HPG axis — because kisspeptin acts at the highest level of reproductive regulation, the long-term consequences of interfering with this system have not been described.

In practice, this means a conditional framework: the data suggest good tolerability under narrowly defined experimental conditions, but no material exists that would justify safety outside them. In the European Union, kisspeptin remains solely a research reagent.

Regulatory status and WADA

Kisspeptin (this product) — a Research Use Only research reagent within EU chemical-reagent supply. The label reads “For research use only. Not for human use”. It is not a medicinal product, a dietary supplement, or a foodstuff. It holds no EMA or FDA registration. In the European Union it is not registered as a medicine or a supplement.

WADA. Kisspeptin does not appear as a separate entry on the current WADA prohibited list. Its status may change in subsequent editions, and the general clauses concerning biologically active substances require independent verification by the researcher.

Frequently asked questions

Does kisspeptin increase testosterone?
The literature does not permit such a claim, and kisspeptin is not a “testosterone booster”. It does not act on testosterone directly — its influence is indirect and proceeds via the HPG axis: stimulation of GnRH neurons leads to an increase in LH secretion, and LH stimulates the Leydig cells to produce testosterone. Studies analysed the influence of kisspeptin administration on LH secretion and, indirectly, on the reproductive axis, but these were mainly observations of an acute, short-term hormonal response under experimental conditions. The data are limited and do not justify treating the peptide as an agent that modifies hormones in humans.

What does the research say about kisspeptin and libido?
Research teams (including the group of Comninos and Dhillo at Imperial College London) studied the influence of kisspeptin on the central processing of stimuli associated with sexual arousal, using brain imaging (fMRI). Modulation of the activity of structures involved in the processing of emotions and stimuli of a sexual nature was observed relative to placebo. These are physiological studies of the mechanism, conducted in small groups under controlled conditions — they describe how the system works, rather than confirming any application outside the laboratory.

How does kisspeptin differ from PT-141?
In its mechanism. Kisspeptin acts hormonally, via the HPG axis and the KISS1R (GPR54) receptor, modifying the cascade GnRH → LH/FSH → sex hormones. PT-141 (bremelanotide) acts centrally, via melanocortin receptors (chiefly MC4R) in the central nervous system, independently of the hormonal axis. They share an area of research interest, but they are two distinct signalling systems.

What is the HPG axis?
The HPG axis (hypothalamic–pituitary–gonadal) is a hierarchical hormonal system governing reproduction. The hypothalamus secretes GnRH (stimulated from above by kisspeptin), GnRH stimulates the pituitary to secrete the gonadotrophins LH and FSH, and these act on the gonads — in men leading to the production of testosterone and to spermatogenesis, in women regulating the maturation of follicles and the production of oestrogens. The sex hormones return as a feedback signal. Within this system, kisspeptin acts as the regulator of the highest level.

Why does kisspeptin come in a nasal spray format?
The nasal spray makes the reagent available as a pre-dissolved solution intended for research into intranasal administration — without the need to reconstitute a lyophilisate. It is worth bearing in mind that the published clinical data on kisspeptin come mainly from injectable administration (intravenous and subcutaneous); the intranasal route remains an exploratory area. The format is intended solely for laboratory work.

Bibliography

1. Comninos AN, Dhillo WS et al. (2017). Kisspeptin modulates sexual and emotional brain processing in humans
2. Jayasena CN et al. (2014). Kisspeptin-54 triggers egg maturation in women undergoing in vitro fertilization
3. George JT et al. (2011). Kisspeptin-10 is a potent stimulator of LH and increases pulse frequency in men
4. The KISS1/KISS1R system in the control of the hypothalamic-pituitary-gonadal axis (review)

Kisspeptin 5 mg nasal spray in the One Peptides catalogue is a reagent intended solely for laboratory and scientific research (Research Use Only). It is not a medicine, a dietary supplement, or a product intended for consumption or administration by humans. Kisspeptin holds no EMA or FDA registration. The description relates to the physiology of the HPG hormonal axis and to the findings reported in the scientific literature — it contains no claims of “increasing testosterone”, “improving libido”, or “affecting potency” in humans, and it describes the influence on the reproductive axis solely within the framework of research. The information is educational and scientific in nature and does not constitute medical or pharmaceutical advice, nor instructions for administration. The reagent is not intended for human use.