Gonadorelin's only pump-delivered FDA approval fired 5 micrograms every 90 minutes, because native GnRH has a 2-to-10-minute initial half-life and a receptor that reads pulse frequency. TRT clinics prescribe one or two injections a week. Nobody has published what that does.
Gonadorelin is the exact decapeptide the hypothalamus releases, it sits in the libido and sexual wellness peptides category, and its gonadorelin compound page carries one of the thinnest lab-test datasets on this platform. It is also one of the very few peptides a US pharmacy may legally compound — for a reason that has nothing to do with whether it works.
Why did the approved gonadorelin product come with a pump?
Lutrepulse, the second FDA-approved gonadorelin product, delivered 5 micrograms every 90 minutes through a programmable pump, because gonadorelin's initial half-life is 2 to 10 minutes and the GnRH receptor responds to pulse frequency rather than dose. Ferring won approval on 10 October 1989 under NDA 019687 for ovulation induction. Its label states that "continuous, non-pulsatile exposure to gonadorelin acetate could temporarily reduce pituitary responsiveness." TRT clinics now inject it once or twice a week.
That label sentence is not a footnote buried in a precautions section. It describes the mechanism by which a completely different class of drugs — leuprolide, goserelin, triptorelin — achieves chemical castration. Give GnRH continuously instead of in pulses and the pituitary stops responding.
A once-weekly injection of a peptide with a 10-to-40-minute terminal half-life leaves only two possibilities, and both are awkward. Either the peptide is cleared within the hour, in which case six days and twenty-three hours of the week are untreated. Or the subcutaneous depot releases it slowly, in which case the injection has produced exactly the continuous non-pulsatile exposure the approved label warns about.
Nobody has published which of those two things happens. That single unanswered question sits underneath every gonadorelin prescription written for fertility preservation.
What is gonadorelin, and why does its half-life matter?
Gonadorelin is native human GnRH-I, the decapeptide pGlu-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-Gly-NH₂, CAS 33515-09-2, molecular weight 1,182.29 g/mol. Its initial half-life is 2 to 10 minutes and its terminal half-life 10 to 40 minutes, among the shortest of any peptide sold in this market. Two modifications carry the activity: a cyclised pyroglutamate at the N-terminus and an amidated C-terminal glycinamide. Both are required for receptor binding, and neither is visible in a purity percentage.
Property | Value |
|---|---|
Sequence | pGlu-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-Gly-NH₂ — a decapeptide |
CAS | 33515-09-2 (PubChem CID 638793) |
Formula / MW | C₅₅H₇₅N₁₇O₁₃ / 1,182.29 g/mol |
Salts | Diacetate 71447-49-9; hydrochloride 51952-41-1 |
Identity | Identical to native human GnRH-I / LHRH |
Half-life | Initial 2–10 minutes; terminal 10–40 minutes |
The two terminal modifications are worth dwelling on, because they are the part of the molecule a certificate of analysis is least likely to address. The N-terminal glutamine cyclises to pyroglutamate; the C-terminus is amidated as glycinamide. A batch with an unblocked N-terminus or a free-acid C-terminus would be a different molecule, inactive, and at a detectably different mass — while still capable of returning a high HPLC purity figure. Mass spectrometry against 1,182.29 Da is the check that catches it. See mass spectrometry for peptides.
The half-life is the whole story. An initial half-life of 2 to 10 minutes means gonadorelin is gone from circulation before most subcutaneous depots have finished absorbing. Every dosing argument in this article is downstream of that number.
What happens when GnRH is delivered continuously instead of in pulses?
Continuous GnRH shuts the pituitary down. Belchetz, Plant, Nakai, Keogh and Knobil showed it in rhesus monkeys in Science in 1978 (PMID 100883): continuous delivery abolished gonadotropin secretion, while intermittent hourly delivery sustained it. An entire drug class exploits that. The FDA label for Lupron (leuprolide acetate) states that "continuous daily administration of leuprolide acetate results in decreased levels of LH and FSH. In males, testosterone is reduced to castrate levels."
This is settled pharmacology, and it is worth establishing from primary documents rather than assertion. Three independent sources say the same thing.
The founding experiment. Belchetz, Plant, Nakai, Keogh and Knobil, Science 1978 (PMID 100883), "Hypophysial Responses to Continuous and Intermittent Delivery of Hypothalamic Gonadotropin-Releasing Hormone." In rhesus monkeys, continuous GnRH abolished gonadotropin secretion; intermittent hourly delivery sustained it. This is animal evidence, and it is why every GnRH-based therapy designed since has been built around pulse frequency.
The approved product's own label. Lutrepulse states that "pulsatile administration of LUTREPULSE replaces defective hypothalamic secretion of GnRH" and "approximates the natural hormonal secretory pattern." Dosing was 5 µg every 90 minutes by pump, subcutaneously or intravenously.
The castration drugs. LUPRON (leuprolide acetate), an FDA-approved GnRH agonist: "following an initial stimulation of gonadotropins, chronic administration of leuprolide acetate results in suppression of ovarian and testicular steroidogenesis"; "continuous daily administration of leuprolide acetate results in decreased levels of LH and FSH. In males, testosterone is reduced to castrate levels."
Read those three together. Pulses stimulate. Continuous exposure suppresses. This is not a subtlety or a theoretical risk — an entire approved drug class is built on the suppressive side of it, and it is used to treat prostate cancer.
Was gonadorelin FDA-approved, and was it withdrawn for safety?
Gonadorelin was FDA-approved twice. Factrel cleared on 30 September 1982 under NDA 018123 as a single 100-microgram diagnostic injection; Lutrepulse cleared on 10 October 1989 under NDA 019687 as a pump-delivered ovulation protocol. Both are discontinued. Gonadorelin is absent from 21 CFR § 216.24, FDA's safety-withdrawal list, but we searched the Federal Register for a notice withdrawing either application and found none. Do not claim an affirmative safety determination exists.
FACTREL | LUTREPULSE KIT | |
|---|---|---|
NDA | 018123 | 019687 |
Approved | 30 September 1982 | 10 October 1989 |
Type | New Molecular Entity, priority review | New Active Ingredient, orphan |
Sponsor | Ayerst / Wyeth-Ayerst (now Hikma) | Ferring |
Form | Gonadorelin hydrochloride, 0.1/0.2/0.5 mg vials | Gonadorelin acetate, 0.8 and 3.2 mg vials |
Indication | "Evaluating the functional capacity and response of the gonadotropes of the anterior pituitary" | "Induction of ovulation in women with primary hypothalamic amenorrhea" |
Dose | 100 µg, single injection — diagnostic | 5 µg every 90 minutes by pump |
Status | Discontinued | Discontinued |
So the two approved human uses were a single-dose diagnostic test and a pump-delivered ovulation induction protocol. Neither is a weekly injection, and neither is a fertility-preservation therapy in men.
On the withdrawal, be careful. Gonadorelin's situation is often described as parallel to sermorelin — FDA-approved, discontinued commercially, formally determined not withdrawn for safety reasons. The first two are true. The third we could not verify.
Gonadorelin does not appear in 21 CFR § 216.24, FDA's list of drug products withdrawn for reasons of safety or effectiveness, and that is a genuine explicit negative. But a search of the Federal Register for a notice withdrawing approval of NDA 018123 or NDA 019687 found none. "Lutrepulse" returns zero documents; "gonadorelin" restricted to FDA returns seventeen, all New Animal Drug notices.
The accurate statement is that Drugs@FDA lists both applications as discontinued and gonadorelin is absent from FDA's safety-withdrawal list. An affirmative published FDA determination of the kind sermorelin has, we did not find.
The one gonadorelin product still marketed in the US is veterinary. Factrel (veterinary) from Zoetis is "Approved by FDA under NADA # 139-237" — gonadorelin 50 µg/mL, cattle only, intramuscular, for ovarian follicular cysts in dairy cows and estrus synchronisation. Cystorelin and Fertagyl are further veterinary products. That matters for a practical reason: the only FDA-approved gonadorelin currently in commerce is made for cows, and any grey-market supply chain has an obvious nearby source.
Why is gonadorelin legally compoundable when most peptides are not?
Gonadorelin is compoundable because USP-NF carries monographs for gonadorelin acetate, gonadorelin hydrochloride and gonadorelin for injection. Under 21 U.S.C. § 353a(b)(1)(A)(i), complying with an applicable USP or National Formulary monograph is one of three statutory routes for a bulk substance in 503A compounding, alongside being a component of an approved drug or appearing on FDA's 503A bulks list. Gonadorelin appears on none of FDA's compounding lists, and does not need to.
That last point is the one almost every page gets wrong. Gonadorelin is not in the active Category 2 group of fourteen substances. It is not on the 503A bulks list. It is not on the 503B list. It is simply absent from all of them — and absence is not the problem it would be for other peptides, because the first statutory prong is already satisfied. A European Pharmacopoeia monograph exists as well.
This is the mechanism that explains gonadorelin's entire market position. It is why gonadorelin sailed through the April 2026 Category 2 sweep that captured kisspeptin-10, ipamorelin and GHRP-2, and why a TRT clinic can prescribe it while the same clinic cannot legally prescribe most of the peptides discussed on this site.
A statutory pathway is not an efficacy finding. It means a licensed pharmacy may compound gonadorelin for a named patient with a valid prescription. It says nothing whatsoever about whether weekly gonadorelin does anything. For how that distinction plays out at the counter, see compounding pharmacy versus research peptide and our FDA peptide regulation timeline.
Is gonadorelin banned in sport?
Yes, explicitly and by name. Section S2.2.1 of the 2026 WADA Prohibited List, headed "Testosterone-stimulating peptides in males," names "gonadotrophin-releasing hormone (GnRH, gonadorelin) and its agonist analogues," listing buserelin, deslorelin, goserelin, histrelin, leuprorelin, nafarelin and triptorelin as examples. Gonadorelin is prohibited at all times, in males. That is a named entry rather than an S0 catch-all inference, and a named entry leaves no interpretive room about whether the compound is covered.
The wording is worth noting for what it implies about detection. A substance listed by name in a specific section, alongside seven named analogues, is a substance anti-doping science has already characterised. Compounds that reach the list only through S0 — the catch-all for unapproved substances — are a different and much weaker position for a testing programme. See do peptides show up on drug tests.
Does gonadorelin match hCG for preserving fertility during testosterone therapy?
No published clinical evidence says it does. Gonadorelin has never been tested in men on exogenous testosterone: ClinicalTrials.gov returns three records for gonadorelin plus testosterone replacement, all unrelated. hCG has direct measurements. Coviello et al. randomised 29 healthy men in 2005 to testosterone enanthate 200 mg weekly plus placebo or hCG, and intratesticular testosterone fell from 1,174 nmol/L to 72 nmol/L on placebo, a 94% collapse, rising linearly with hCG dose (P<0.001).
What hCG has been shown to do. Coviello et al. 2005 (JCEM, PMID 15713727) randomised 29 healthy men to testosterone enanthate 200 mg weekly plus placebo or hCG at 125, 250 or 500 IU every other day for three weeks, with intratesticular testosterone measured directly. Baseline ITT was 1,174 nmol/L; in the placebo arm it fell to 72 nmol/L. ITT "increased linearly with increasing hCG dose" (P<0.001).
Hsieh et al. 2013 (J Urol, PMID 23260550) followed 26 men on testosterone replacement receiving concomitant hCG 500 IU intramuscularly every other day, mean follow-up 6.2 months. Semen parameters remained stable beyond one year. No participant became azoospermic, and nine of 26 achieved partner pregnancy.
What gonadorelin has been shown to do in this setting: nothing has been published. ClinicalTrials.gov for gonadorelin plus testosterone replacement returns three records, all unrelated — pain sensitivity, androgen metabolism and muscle, and regional fat metabolism. PubMed searches for gonadorelin in men on exogenous testosterone return no trials; every hit is pump-delivered GnRH in hypogonadotropic hypogonadism, a different clinical problem, or hCG studies.
The most telling negative is a review, not a trial. Fink, Ide and Horie, "Management of Male Fertility in Hypogonadal Patients on Testosterone Replacement Therapy" (Medicina, 2024), is devoted to exactly this question. It enumerates short-acting testosterone formulations, hCG, aromatase inhibitors and SERMs, and does not mention gonadorelin at all. A specialist review of the exact clinical question does not consider it an option.
The nearest real evidence for GnRH as a therapy in men is Liu et al. 1988 (Fertil Steril, PMID 3123278), comparing pulsatile subcutaneous GnRH by pump against exogenous gonadotropins in isolated hypogonadotropic hypogonadism. Pump delivery, different population, different question.
Gonadorelin | hCG | |
|---|---|---|
Site of action | Pituitary — releases LH and FSH | Testicular LH receptors — bypasses the pituitary |
Delivery the evidence used | Pump, 5 µg every 90 minutes | 500 IU intramuscularly, every other day |
Human endpoint measured | LH response, ovulation induction | Intratesticular testosterone; semen parameters |
Published data in men on TRT | None found | Coviello 2005 (n=29, RCT); Hsieh 2013 (n=26) |
Azoospermia outcome | Never measured | No participant became azoospermic |
Schedule the evidence supports | 90-minute pulses | Every other day |
That table is the reason clinicians who study this problem reach for hCG. For the three-way version of the same question, see kisspeptin versus gonadorelin versus hCG.
Which gonadorelin claims survive the evidence?
Two of nine. Gonadorelin was genuinely FDA-approved twice and is genuinely compoundable through the USP monograph prong; those hold. The rest do not. Fertility maintenance on testosterone therapy is unstudied, equivalence with hCG is not shown, weekly dosing is pharmacologically incoherent against a 2-to-10-minute initial half-life, the claim that continuous exposure is harmless is contradicted by the approved label, and the only FDA-approved gonadorelin now marketed in the US is veterinary.
Claim | Evidence | Verdict |
|---|---|---|
Was FDA-approved | Twice — Factrel 1982, Lutrepulse 1989 | True |
FDA determined it safe when withdrawn | Absent from 21 CFR § 216.24, but no affirmative FR determination found | Unverified |
Legally compoundable | Yes — via the USP monograph prong | True |
Maintains fertility on TRT | No published clinical evidence | Unstudied |
As good as hCG for this | hCG has direct ITT and semen-parameter data; gonadorelin has none | Not shown |
Weekly dosing is appropriate | Half-life 2–10 min initial, 10–40 min terminal; approved product used 90-minute pulses | Pharmacologically incoherent |
Continuous exposure is harmless | Label: "could temporarily reduce pituitary responsiveness"; the basis of chemical castration | Contradicted |
Only FDA-approved gonadorelin is human | The marketed US product is veterinary (NADA 139-237) | Reversed |
Not banned in sport | WADA S2.2.1, named explicitly | False |
Both surviving claims are about paperwork — an approval history and a statutory pathway. Neither is about an effect in a person.
How far is the clinic protocol from the approved one?
About a hundred-fold apart on frequency. The approved Lutrepulse protocol delivered 5 micrograms every 90 minutes by programmable pump, roughly 112 doses a week. TRT clinic protocols typically use 100 to 200 micrograms or more, once or twice weekly, by manual subcutaneous injection. That is 1 to 2 doses a week against roughly 112, from a molecule whose approved label warns that continuous, non-pulsatile exposure could temporarily reduce pituitary responsiveness.
Approved therapeutic use | TRT clinic protocol | |
|---|---|---|
Dose | 5 µg | Typically 100–200+ µg |
Interval | Every 90 minutes | Once or twice weekly |
Delivery | Programmable pump | Manual subcutaneous injection |
Doses per week | ~112 | 1–2 |
Evidence | Approved indication | None published |
There are two possible defences of weekly gonadorelin, and both are testable and untested. The first is that a large subcutaneous bolus produces a single supraphysiological pulse that transiently stimulates LH and FSH enough to matter. That is plausible, and demonstrating it would require semen parameters or intratesticular testosterone, which nobody has measured. The second is that slow depot absorption creates sustained low-level exposure — which is precisely the pattern that downregulates the receptor.
Nobody has published which of these happens. That is the state of the evidence, and it is not a small gap for a drug prescribed to preserve fertility.
What do seven lab tests and three shops in stock tell you?
Gonadorelin has one of the thinnest datasets on this platform. The Purity Index records 99.48% average purity across just 7 independent HPLC tests run between April 2025 and May 2026 (verified August 2026), from Ethos Analytics, Freedom Diagnostics, Vanguard, Bioviridian and Janoshik, against 219 verified vendors. One of those seven is alarming: a product labelled 5 mg tested at 2.12 mg, a 57.6% shortfall, in April 2025 via Vanguard Laboratory.
That is not a fill-accuracy wobble. It is less than half the labelled content, on a compound where the dose is already unvalidated. The other six tests returned 99.00–99.87% purity with overages of 1.7% to 16.1%.
Gonadorelin price data shows just 3 shops in stock, median $8.00/mg, lowest $6.40/mg on a 10 mg vial, highest $44.99/mg on a 2 mg vial (verified 8 August 2026). Those figures exclude shipping, taxes and customs, coupon codes, bulk tiers, multi-vial kits and account-gated pricing. They sit inside a platform tracking 530 shops and 11,852 independent lab tests across 118 peptides, with 1,283 community reviews (verified August 2026).
Three shops in stock against 219 known vendors, on a compound that is legally compoundable, is an unusual pattern and a readable one. It is consistent with most legitimate demand flowing through prescriptions and compounding pharmacies rather than research vials — which, for once, is the healthier structure.
Check | What it confirms | How | Red flag |
|---|---|---|---|
Mass spectrometry | Gonadorelin at 1,182.29 Da with pyroglutamate and C-terminal amide intact | Batch-matched CoA with MS | HPLC purity only |
Fill accuracy | Vial matches label | Quantitative content testing | A 57.6% shortfall is on record for this compound |
Salt form | HCl versus acetate versus free base | Salt form stated on the CoA | Not stated |
Net peptide content | Peptide versus salt and water | Net content or amino acid analysis | Purity quoted as quantity |
Endotoxin (LAL) | No pyrogens | LAL result on the batch | Field blank |
Compare vendors on the gonadorelin compound page, and read the wider body of independent lab tests for how coverage on this compound compares with better-tested peptides.
One correction to our own page. The gonadorelin compound page currently states that gonadorelin "was FDA-approved as Factrel (1989, discontinued from US market 2020 for commercial reasons)." Factrel was approved 30 September 1982 under NDA 018123; 1989 is the Lutrepulse approval date under NDA 019687. The 2020 discontinuation date and the "commercial reasons" attribution are not supported by any FDA document we could locate. That page is being corrected.
The trial that would settle this
The trial that would settle gonadorelin is a randomised comparison in men on testosterone replacement, against hCG 500 IU every other day, with intratesticular testosterone or semen parameters as the primary endpoint rather than LH. It would need weekly, twice-weekly and pulsatile arms, an LH response measured after week 8 to detect desensitisation, and at least 6 months of follow-up, because spermatogenesis takes about 74 days. No such trial exists.
Element | Requirement | Why |
|---|---|---|
Population | Men on testosterone replacement | The actual use case, never studied |
Comparator | hCG 500 IU every other day | The regimen with published semen and ITT data |
Primary endpoint | Intratesticular testosterone or semen parameters | LH is a proxy; ITT is what fertility depends on |
Regimen arms | Weekly vs twice-weekly vs pulsatile | Nobody knows which, if any, works |
Pharmacodynamics | LH response after week 8 | Tests whether desensitisation occurs — the central risk |
Duration | 6+ months | Spermatogenesis takes about 74 days |
The pharmacodynamics row is the one that matters most. If weekly gonadorelin desensitises the pituitary over time, a man taking it to preserve fertility could be achieving the opposite of what he intends. Nobody has measured that.
Frequently Asked Questions
Was gonadorelin ever FDA-approved?
Yes, twice. Factrel was approved in September 1982 for diagnostic evaluation of pituitary gonadotrope function, and Lutrepulse in October 1989 for ovulation induction in primary hypothalamic amenorrhoea. Both are discontinued. The only FDA-approved gonadorelin currently marketed in the US is veterinary, under NADA 139-237, for cattle.
Why can clinics compound gonadorelin when most peptides are off-limits?
Because USP monographs exist for gonadorelin acetate, gonadorelin hydrochloride and gonadorelin for injection. Under 21 U.S.C. § 353a(b)(1)(A)(i), complying with a USP monograph is one of three statutory routes for a bulk substance in 503A compounding. That is a legal pathway, not an efficacy endorsement.
Does gonadorelin preserve fertility during testosterone therapy?
No published clinical evidence supports this. We found no trial of gonadorelin in men on exogenous testosterone, and a 2024 specialist review of fertility management during testosterone replacement does not mention gonadorelin as an option. hCG, by contrast, has direct intratesticular testosterone data and semen parameter data.
Why does the dosing frequency matter so much?
Gonadorelin's initial half-life is 2 to 10 minutes and its terminal half-life is 10 to 40 minutes. The approved therapeutic product delivered 5 µg every 90 minutes by pump — about 112 doses a week — because GnRH receptor signalling is frequency-dependent. Continuous or non-pulsatile exposure downregulates the receptor, and that is the mechanism GnRH agonists like leuprolide use to reduce testosterone to castrate levels.
Is gonadorelin the same as hCG?
No. They act at different points in the axis. Gonadorelin acts on the pituitary to release LH and FSH; hCG acts directly on testicular LH receptors, bypassing the pituitary entirely. That is why hCG works on a twice-weekly schedule and gonadorelin's approved product needed a pump.
Is gonadorelin banned in sport?
Yes, by name. WADA's 2026 Prohibited List, section S2.2.1, lists "gonadotrophin-releasing hormone (GnRH, gonadorelin) and its agonist analogues" among testosterone-stimulating peptides in males. Prohibited at all times.
Where gonadorelin sits
Gonadorelin is the most legally clean compound in the fertility and hormone-axis category and the one whose real-world use has drifted furthest from its pharmacology. Two FDA approvals, USP monographs in three forms, a statutory compounding route most peptides cannot reach, and a molecule identical to native GnRH — all of that is solid. What is missing is any published evidence that once- or twice-weekly injection does what men are taking it to do.
The approved product came with a pump because a peptide with a 10-to-40-minute terminal half-life, acting on a receptor that responds to pulse frequency, cannot be dosed any other way. The label says non-pulsatile exposure could temporarily reduce pituitary responsiveness. An entire class of prostate cancer drugs is built on that fact, and a 1978 primate experiment established it before any of those drugs existed.
Weekly subcutaneous gonadorelin might work anyway. A large bolus producing one strong pulse is not an absurd idea, and we are not asserting that it fails. We are pointing out that it is an untested idea, prescribed to men whose specific goal is preserving fertility, when the alternative on the shelf has direct intratesticular testosterone measurements behind it and a published record of no participant becoming azoospermic.
Browse the libido and sexual wellness peptides category, or our complete peptide guide with 118 compounds (verified August 2026). For per-injection volume, use the peptide dosing calculator alongside the reconstitution calculator. Compare shops through independent lab tests and community-verified shop reviews.
This article is for educational and informational purposes only and does not constitute medical advice. Peptides discussed may be investigational compounds not approved by the FDA (or equivalent regulators in your jurisdiction) for human use. Always consult a qualified healthcare provider before using any peptide or research compound. Peptigrity is an independent review platform and does not sell, endorse, or recommend specific products or vendors.
