Kisspeptin’s hormone response depends on the dosing pattern.

Why this note exists

Most compounds in this index are thinly studied. Kisspeptin is the opposite problem: a real and often elegant body of human physiology, run by named academic groups, published in JCI, JAMA Network Open and Human Reproduction — and pointed almost entirely at questions the research market is not asking. The trials are about triggering ovulation in IVF, probing GnRH neuron function in delayed puberty, and imaging the brain in low sexual desire. The vials are sold to men who want testosterone.

In the index generated on August 15, 2026, 67 of 112 vendors carried a kisspeptin listing — 84 listings, twentieth of 83 compounds by vendor coverage, 78 of them in stock.[28] Fifty-five of the 84 are 10 mg vials and fifteen are 5 mg.[28] And 30 of the 84 name the isoform: they say "Kisspeptin-10." The other 54 say only "Kisspeptin," which is the name of a family, not of a molecule.[28]

A note on what kind of evidence this is: every participant count, route and endpoint below comes from a human study or an FDA review of human studies, and carries its design. Two paragraphs report mouse and cell data and are labeled as such in the same sentence as the finding. Where a dose appears it appears as its source published it, with route and units intact — pepmg does not convert an infusion rate into a vial, and there is no arithmetic in this note that turns nmol/kg/h into milligrams.

The regulatory record

FDA looked at exactly this product, and wrote down what it found

In 2015 a compounding pharmacy nominated kisspeptin-10 for the 503A Bulks List — the list of bulk substances that compounding pharmacies are permitted to use. The proposed use, as FDA recorded it, was "[h]ormonal therapy to include treatment of male hypogonadism, preservation of spermatogenesis with testosterone therapies," and the proposed products were "1 mg/mL solutions for injection for subcutaneous (SC) and intramuscular (IM) administration."[1] That is, almost precisely the product the research market sells and the use it is sold for.

FDA's review team — a chemist, a pharmacology/toxicology reviewer, a clinical analyst and a lead physician — filed its evaluation on July 5, 2024.[1] The opening is unambiguous: "There is no applicable United States Pharmacopeia (USP) or National Formulary (NF) drug substance monograph for kisspeptin-10, and kisspeptin-10 is not a component of an FDA-approved drug," and after weighing characterization, historical use, safety and effectiveness, "we believe the evaluation criteria weigh against placing kisspeptin-10 on the list."[1]

The Pharmacy Compounding Advisory Committee met on October 29, 2024 and took four substance votes. The kisspeptin-10 question was worded as FDA words all of them — "FDA is proposing that Kisspeptin-10 NOT be included on the 503A Bulks List. Should Kisspeptin-10 be placed on the list?" The result: Yes: 0, No: 11, Abstain: 0.[2] The minutes summarize the discussion in one sentence: "The committee unanimously agreed that Kisspeptin-10 should not be included on the 503A Bulks List due to the lack of convincing safety and efficacy data."[2]

What that vote is and is not: it is advice to FDA about pharmacy compounding, approved as summary minutes on January 15, 2025.[2] It is not a finding that kisspeptin is dangerous, and it is not a drug approval decision — no application to approve kisspeptin as a medicine has ever been before the agency.[3][4] The committee's stated reason was absence of evidence, which is a different claim from evidence of absence, and this note keeps them apart.

The finding that repeats

2009, 2010, 2026: give it again and the response fades

The kisspeptin literature has one result that has now been reproduced across seventeen years, two isoforms, two routes and both sexes. It is not an efficacy result. It is that the axis stops answering.

The 2009 study is the cleanest statement of it. Women with hypothalamic amenorrhea were randomized, double-blinded, in a parallel design, to twice-daily subcutaneous kisspeptin-54 at 6.4 nmol/kg or to saline — five women per group, for two weeks.[6] On the first injection day the mean maximal rise within four hours was 24.0 ± 3.5 IU/L for LH and 9.1 ± 2.5 IU/L for FSH. On the fourteenth injection day the same measurements were 2.5 ± 2.2 and 0.5 ± 0.5 IU/L (P < 0.05).[6] The pituitary itself was fine — subjects still responded to GnRH — and no significant change in LH pulsatility or on ultrasound was observed over the two weeks.[6] Its title says the finding out loud: chronic administration causes tachyphylaxis.

Participant counts and results as reported in each paper. The 2010 study is a follow-up in the same condition by the same group; its abstract reports the pattern rather than a headline number.[6][7][5]

The 2010 follow-up did the useful thing and mapped the time course. On twice-daily kisspeptin-54, "responsiveness to luteinizing hormone (LH) diminished gradually, whereas responsiveness to follicle-stimulating hormone (FSH) was nearly abolished by day 2." Twice-weekly dosing "resulted in only partial desensitization, in contrast to the complete tolerance achieved with twice-daily administration," and women with hypothalamic amenorrhea on the twice-weekly schedule had significantly elevated reproductive hormones at eight weeks compared with saline, with no adverse effects observed.[7]

Which brings this to the paper published on August 3, 2026 — the reason this note is being written now, and the first study to run the question with kisspeptin-10 under the skin. It was a randomized, single-blinded, placebo-controlled study at Imperial College London in 15 healthy men, split across three sub-studies (n = 7, n = 4 and n = 7), with 12 men serving as controls.[5] Acute eight-hour subcutaneous infusions at 1.25–10.0 nmol/kg/h raised LH, FSH and testosterone dose-dependently against vehicle (P < .0001).[5] Five days of continuous infusion at 180 nmol/h, in four men, left testosterone elevated but gonadotropins "similar to vehicle."[5] Daily eight-hour infusions at 150 nmol/h over 12 days did sustain the gonadotropin rise — mean LH increase +1.68 ± 0.25 on day 1 and +1.14 ± 0.33 on day 12, against −0.16 ± 0.19 on vehicle, P = .003 — and a bolus at the end still worked, which the authors read as the receptor remaining functional.[5]

Read the conclusion as written. The authors state that they "demonstrate that chronic subcutaneous kisspeptin administration sustains gonadotropin and testosterone secretion in healthy men for 12 days," and that the data "can inform development of chronic kisspeptin administration protocols for the treatment of reproductive disorders."[5] That is a protocol-development finding in healthy volunteers, delivered by infusion, over twelve days. It is not a treatment result, there was no patient population, and no clinical outcome was measured.

The gap

The dose form in the trials is a pump. The dose form on sale is a vial.

Nearly every human kisspeptin study delivers the peptide as a timed infusion in a clinical research unit — intravenous or subcutaneous, at a rate in nmol/kg/h, with cannulated blood sampling. That is not an incidental detail of study design; it is a response to the pharmacology. In mouse work published in 2017, kisspeptin-54 had a bloodstream half-life of about 32 minutes and kisspeptin-10 about 4 minutes; repeating kisspeptin-10 injections every ten minutes for an hour failed to reproduce the sustained LH rise a single kisspeptin-54 injection produced, and only kisspeptin-54 activated c-FOS in GnRH neurons behind the blood-brain barrier.[21] That paragraph is mouse data, and the authors present it as a mechanistic explanation for a difference already seen after peripheral dosing.[21]

In humans the two isoforms have been compared directly once. In a single-blinded, placebo-controlled physiology study run through 2013, healthy men received vehicle, kisspeptin-10, kisspeptin-54 and GnRH intravenously for three hours on separate days at 0.1, 0.3 and 1.0 nmol/kg/h, with five subjects per dosing group.[8] At the doses tested the two kisspeptins produced similar gonadotropin secretion; GnRH produced roughly three times the LH area-under-curve of kisspeptin-10 and about twice that of kisspeptin-54 (10.81 ± 1.73, 14.43 ± 1.27 and 34.06 ± 5.18 h·IU/L at the top dose).[8] The paper's own listed limitation is the sample size.[8]

The closest thing in the literature to the marketed use is a 2013 study in Edinburgh that gave an intravenous kisspeptin-10 bolus of 0.3 mcg/kg to five hypotestosteronaemic men with type 2 diabetes and seven age-matched healthy men. Mean LH rose from 5.5 ± 0.8 to 13.9 ± 1.7 IU/L in the healthy men (P < 0.001) and from 4.7 ± 0.7 to 10.7 ± 1.2 IU/L in the men with diabetes (P = 0.02), with comparable increments.[10] It is titled as what it is — an exploration of pathophysiology — and its second experiment ran in four men.[10] Earlier work established that intravenous kisspeptin-10 raises LH and increases pulse frequency in men, and that kisspeptin-54 stimulates the axis in human males.[9][11] All of it is acute-response physiology. None of it followed anyone for a clinical outcome.

Meanwhile the delivery problem is being worked on in the open. A 2025 paper in EBioMedicine reported a randomized, double-blinded, crossover, placebo-controlled study of intranasal kisspeptin-54 in healthy men, healthy women and patients with hypothalamic amenorrhea, with mean maximal LH increases of 4.4 ± 0.6, 1.4 ± 0.3 and 4.4 ± 0.2 IU/L against placebo, and no adverse events reported; the authors describe the invasive routes as "markedly limit[ing] patient acceptability and clinical use."[15] The same paper's mechanistic half is in mice, and says so.[15]

The libido trials

Thirty-two people, seventy-five minutes, and an fMRI scanner

These are the two studies most often cited in kisspeptin marketing, and they are good studies. They are also not what they are usually described as.

The women's trial, published in JAMA Network Open in October 2022, was a double-masked, placebo-controlled two-way crossover in premenopausal women with hypoactive sexual desire disorder at a single UK university research center. Forty were randomized; 32 completed both visits. The intervention was a 75-minute intravenous infusion of kisspeptin-54 at 1 nmol/kg/h against a rate-matched placebo, and the main outcome was blood-oxygen-level-dependent response across the whole brain and in regions of interest during erotic and facial-attraction stimuli.[12] It reported modulations in specific regions, correlations between kisspeptin-enhanced hippocampal activity and baseline sexual distress (r = 0.469, P = .007), and that kisspeptin "was well-tolerated with no reported adverse effects." Its stated conclusion is that the findings "lay the foundations for clinical applications."[12]

The men's trial, published in February 2023, used the same design and the same infusion in right-handed heterosexual men with the same diagnosis: 37 randomized, 32 completed, mean age 37.9.[13] The primary outcome was again whole-brain fMRI activity, which was modulated versus placebo (mean absolute change, Cohen d = 0.81 [95% CI, 0.41–1.21]; P = .003).[13] The results people quote came from the secondary analyses, and the paper labels them as such: penile tumescence in response to sexual stimuli increased "by up to 56% more than placebo" (mean difference 0.28 units [95% CI, 0.04–0.52]; P = .02), and "happiness about sex" rose 0.63 points [95% CI, 0.10–1.15]; P = .02.[13]

A single infusion in a scanner is a mechanism experiment. It cannot speak to what repeated dosing does, which is the one thing the rest of this literature has consistently found something about. A 2025 review in Trends in Endocrinology & Metabolism — written by an author who discloses a pending patent application on kisspeptin receptor agonists for modulating sexual desire — frames the state of play as promise plus unsolved problems, and says improving delivery methods "will be key."[14] That disclosure is in the paper and belongs next to the citation.

Where the record is strongest

One dose, in an IVF clinic, for something else entirely

Kisspeptin's best human evidence is for triggering egg maturation, and it is the mirror image of chronic dosing: a single injection, once, at a defined point in a stimulated cycle.

The 2014 report in the Journal of Clinical Investigation gave 53 women undergoing IVF a single subcutaneous injection of kisspeptin-54 across four dose levels (1.6 to 12.8 nmol/kg) to induce an LH surge, with eggs retrieved 36 hours later and maturation as the primary outcome. Fertilization and embryo transfer occurred in 92% (49/53); biochemical and clinical pregnancy rates were 40% (21/53) and 23% (12/53).[16] That is a dose-ranging study without a comparator arm, and it is registered as NCT01667406.[24] A 2015 report in JCEM extended the approach to women at high risk of ovarian hyperstimulation syndrome.[17]

The randomized work followed in 2017: a phase 2 placebo-controlled trial in 62 women at high risk of OHSS, all of whom received kisspeptin-54 at 9.6 nmol/kg 36 hours before retrieval, then randomized 1:1 to a second dose or saline ten hours later, with patients, embryologists and clinicians blinded. Its answer was that the second dose improved oocyte yield.[18] An industry program followed the same logic into a longer-acting receptor agonist, MVT-602, reported in Fertility and Sterility in 2024 from two randomized, placebo-controlled trials in healthy premenopausal women, sponsored by Myovant Sciences.[19]

Note what all of that shares: a single administration, a defined biological moment, and an outcome measured within days. It is the use case in which kisspeptin's short action is an advantage rather than the problem to be engineered around.

The other direction

The same receptor was also developed as a way to lower testosterone

Continuous agonism at a GnRH-upstream receptor does not have one obvious direction, and industry has pursued both. Takeda's kisspeptin-analogue program, TAK-448, appears in the registry three times: a phase 1/2 study in men with prostate cancer titled, in the sponsor's own words, to assess "Testosterone-Lowering Efficacy"; a phase 2 study in middle-aged and older men with low testosterone; and a phase 2a study in hypogonadotropic hypogonadism. All three are listed as terminated.[26][23] TAK-448 is an analogue rather than kisspeptin-10 itself, and the registry gives status, not the reason a sponsor stopped.[23]

Academic work has explored the suppressive direction deliberately too. Massachusetts General Hospital has a completed phase 1 study of eight participants titled "Dampening the Reproductive Axis With Continuous Kisspeptin."[25] A registry search for kisspeptin as an intervention on August 29, 2026 returned 36 studies — 25 interventional and 11 observational, of which 23 are completed, 6 recruiting, 4 terminated and 2 withdrawn.[23] The largest interventional entries are physiology and IVF studies; Imperial College London also lists a study of reproductive hormones during sustained administration of kisspeptin with an estimated enrollment of 76, still recruiting.[27] The search matches records where kisspeptin is measured rather than given, so the interventional count is a ceiling, not a tally of dosing trials.[23]

Safety

Well tolerated in the exposures studied — which are hours, not months

Acute human administration has a clean short-term record in the published trials. The 2022 HSDD trial reported kisspeptin "well-tolerated with no reported adverse effects"; the 2025 intranasal study reported no side effects or adverse events; the 2010 eight-week twice-weekly study reported none observed.[12][15][7] FDA's review agrees as far as it goes: "Acute administration of IV kisspeptin-10 has not raised any major safety concerns in studies to date." The sentence continues: "However, there are no data on adverse events for the doses and frequencies of dosing in the context of treatment of diseases in men with reproductive disorders."[1]

Two concerns in FDA's review are about the product rather than the molecule, and they are the ones a vial buyer cannot check. First, characterization: FDA "could not find information on the nature and control of individual peptide-related impurities, including aggregates, and variants," and concluded the substance "is not well characterized from the physical and chemical characterization perspective."[1] Second, immunogenicity: "As a peptide with 10 amino acids that is administered through a parenteral route of administration (SC and IM), kisspeptin-10 may pose a significant risk for immunogenicity, potentially amplified by aggregation as well as potential peptide-related impurities."[1] The advisory committee heard a dedicated FDA presentation that afternoon on immunogenicity risk of compounded peptides.[2]

Animal and cell data, labeled as such: FDA's review notes that "[a]ccording to nonclinical pharmacological studies, tachyphylaxis can develop when kisspeptin-10 is administered uninterruptedly for a long period, rendering kisspeptin-10 pharmacologically inactive," and that "although the pro-atherosclerotic effects of kisspeptin-10 are concerning, their clinical relevance remains unclear."[1] The atherosclerosis finding is a 2017 study in human cell culture and in apolipoprotein-E-deficient mice, in which four weeks of kisspeptin-10 infusion accelerated aortic plaque development, an effect abolished by a GPR54 antagonist.[22] That is mouse and in vitro work. It has not been shown in people, and FDA said so in the same breath as raising it. FDA also recorded that "nonclinical toxicity studies available at the time of this evaluation were too limited in scope and duration to inform safety considerations."[1]

The market

A family name on a vial

The naming problem here is not cosmetic. Kisspeptin-10 and kisspeptin-54 are different molecules with different half-lives and, in mice, different access to the brain.[21] Most of the human trials used kisspeptin-54; the nominated and reviewed compounding substance was kisspeptin-10; and 54 of the 84 listings in pepmg's index name neither, saying only "Kisspeptin."[28] A buyer reading a trial result and a product page cannot always tell whether they are looking at the same compound, and pepmg tracks the listings as vendors published them without inferring which isoform is in any vial.

FDA noticed the same drift from a different angle. Its review records that a FAERS case report indicated a compounded injectable kisspeptin-10 product being used for hypogonadotropic hypogonadism, and that "[t]he most common uses of kisspeptin products on several clinics' websites are weight loss and fertility."[1] There is no human weight-loss trial of kisspeptin in this record at all. FDA also found "insufficient information available to determine how long kisspeptin-10 has been used specifically in pharmacy compounding."[1]

Three things this note is not saying

First, it is not saying kisspeptin is a fake target. It is a genuine and central regulator of the reproductive axis — people with inactivating mutations in kisspeptin signaling are infertile, and the physiology has held up across a large peer-reviewed literature summarized in a 2025 Physiological Reviews article.[16][20]

Second, it is not saying the acute effects are unreal. Multiple independent groups have shown that kisspeptin raises LH, FSH and testosterone acutely in humans, including in men with mild biochemical hypogonadism.[9][10][5] The August 2026 study extends that to twelve days on an intermittent subcutaneous schedule in healthy men.[5]

Third, it is not saying the advisory vote settles the science. The committee voted on whether a compounding pharmacy may use the substance, on the record available in 2024, and its stated reason was a lack of convincing data — which the 2026 paper adds to rather than resolves.[2][5]

What it is saying is narrower. The question "does kisspeptin work" has been asked and answered for a laboratory endpoint — hormones move — and never asked at all for the thing on the label. No trial has given kisspeptin-10 repeatedly to men with low testosterone and measured whether anything improved. The one design question that has been studied repeatedly, in three separate papers across seventeen years, is what happens when you keep dosing, and the answer each time was that the response fades unless the schedule leaves gaps.[6][7][5]

Questions people are asking