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Gonadorelin Guide: Evidence & Sourcing

Gonadorelin is a synthetic decapeptide with the same amino acid sequence as endogenous gonadotropin-releasing hormone (GnRH). This page summarizes what the published record shows about it — the trials, their doses, the two withdrawn US human products, and the questions the literature does not answer. Educational use only, not medical advice.

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Gonadorelin Guide: Available Now

Educational use only — not medical advice. This guide summarizes information reported in published research and community practice for educational purposes. It is not medical advice and not a recommendation to use any compound. Any doses, schedules, or combinations shown are examples of what has been reported, not instructions for you. Many peptides described here are research compounds that are not FDA-approved for the uses discussed and may be investigational or restricted. Effects, risks, and legal status vary; individual needs and results vary. Consult a qualified, licensed healthcare professional before making any decision. Do not use this content to diagnose, treat, or dose yourself.

Gonadorelin at a glance

What it is
Synthetic gonadotropin-releasing hormone (GnRH): pGlu-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-Gly-NH2, ten residues, sequence-identical to the endogenous hypothalamic hormone. PubChem CID 638793, C55H75N17O13, 1182.3 g/mol (monoisotopic 1181.573), CAS 33515-09-2
US human approval status
Two human products were approved and both are listed Discontinued in Drugs@FDA: Factrel (NDA 018123, gonadorelin hydrochloride, 100/200/500 mcg vials) and the Lutrepulse Kit (NDA 019687, gonadorelin acetate, 0.8 mg and 3.2 mg vials) for pump delivery
What still carries a live US label
Five gonadorelin products, all veterinary: Factrel (Zoetis), Cystorelin, Fertagyl, GonaBreed and OvaCyst — cattle labels for follicular cysts and estrous synchronization
What published human protocols dosed
A pulse every 90 minutes from an infusion pump: 5 mcg per pulse in 7 male infants (PMID 40099791), 7-15 mcg per pulse in 45 men (PMID 39210488), 20 mcg per pulse in 19 women (PMID 9174849)
What the market describes instead
50-200 mcg per subcutaneous injection, two to three times weekly, or 100-150 mcg daily to every other day. These are figures reported in clinic and community sources, not trial protocols
The gap between those two rows
A PubMed title/abstract search pairing gonadorelin with "twice weekly" or "three times weekly" returns no records, and pairing it with "intermittent" and "subcutaneous" returns none either. The frequency the market uses has not been studied
Plasma half-life (corrected on this page)
The human intravenous measurement needs three exponentials: 2-4 minutes, 30-55 minutes, and a third component beyond 10 hours (radioiodinated tracer, 3 male volunteers, PMID 4577100). A radioimmunoassay study gives disappearance half-times of 4-6 minutes (PMID 1100364)
Compared with hCG
One published head-to-head study: 28 azoospermic men with congenital hypogonadotropic hypogonadism, 10 on a pulsatile gonadorelin pump versus 18 on hCG/hMG. Median time to spermatogenesis 6 versus 14 months (PMID 30569789). The gonadorelin arm was a pump, not an injection schedule
Why the comparison is being asked at all
FDA's compounding notice of 23 March 2020 states that transitioning biological products are not eligible for the compounding exemptions in sections 503A and 503B, and names human chorionic gonadotropin among the bulk substances outsourcing facilities had reported using
Solution stability
Gonadorelin in aqueous solution is most stable at pH 5-5.5; degradation follows Arrhenius behaviour and is independent of acetate, phosphate, borate and carbonate buffer concentration (PMID 8897270)
What the cattle label says about an opened vial
The Factrel (Zoetis) label directs storage at 2-8 C and to "use contents within 1 month of first vial puncture", and the formulation carries 2% benzyl alcohol as a preservative
Literature size
295 PubMed records name gonadorelin in title or abstract. The broader indexed query expands to 43,233 records because it sweeps in the whole GnRH-analog literature, and a large share of the genuine gonadorelin set is veterinary
Sport
Gonadotrophin-releasing hormones are covered by the WADA Prohibited List, which is reissued annually. Anyone subject to anti-doping rules should check gonadorelin's current entry in GlobalDRO rather than rely on any summary, including this one

Educational reference. This page does not publish dose ranges or reconstitution arithmetic.

What it is / mechanism

Gonadorelin is a synthetic decapeptide with the identical amino acid sequence to endogenous gonadotropin-releasing hormone: pGlu-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-Gly-NH2, PubChem CID 638793, C55H75N17O13, 1182.3 g/mol, CAS 33515-09-2. Because it is the native hormone rather than an analog, it carries none of the modifications that make leuprorelin, goserelin, triptorelin or nafarelin long-acting, and it inherits the native hormone's kinetics instead. It is reported to act as an agonist at GnRH receptors on anterior pituitary gonadotroph cells, prompting release of luteinizing hormone (LH) and follicle-stimulating hormone (FSH), which in turn signal the gonads. The defining feature described throughout the literature is frequency dependence: delivery that mimics natural hypothalamic pulsing sustains gonadotropin output, whereas continuous exposure downregulates and desensitizes the receptor and suppresses LH and FSH — which is precisely how the long-acting analogs are used to shut the axis down in prostate cancer and endometriosis. The same molecule, delivered on a different schedule, produces opposite effects. That is why every human protocol below is described by its interval first and its dose second.

Researched effects

The human record for gonadorelin itself is small, modern in part, and almost entirely pump-based. In congenital hypogonadotropic hypogonadism, a 2025 series treated 7 male infants with subcutaneous pulsatile gonadorelin at 5 mcg every 90 minutes for 3 to 5 months and reported penile length rising from 1.27 plus or minus 0.71 cm to 2.43 plus or minus 0.90 cm with measurable testicular growth (PMID 40099791). A 2024 retrospective series treated 45 men with 7 to 15 mcg per pulse every 90 minutes over a mean 19.1 plus or minus 4.3 months, reporting significant rises in FSH, LH and testosterone, though 6 men with cryptorchidism did not reach a normal testosterone level within the follow-up (PMID 39210488). In women, a 1997 study gave 20 mcg pulses every 90 minutes by portable subcutaneous pump to 19 patients diagnosed with hypothalamic amenorrhea; 14 ovulated in the first treatment cycle (PMID 9174849). Historically the same molecule was used as a single-injection diagnostic challenge of pituitary gonadotropin reserve, which is what the withdrawn Factrel human product was approved for. Outside those settings the record thins quickly: these are published findings in defined patient groups, not outcomes that transfer to other populations or schedules.

Evidence & regulatory status

  • Head-to-head with hCG, once: 28 azoospermic men with congenital hypogonadotropic hypogonadism, 10 given a pulsatile gonadorelin pump and 18 given cyclical hCG/hMG. Median time to spermatogenesis was 6 months on the pump versus 14 months on gonadotropins (chi-square 6.711, p = 0.01); spermatogenesis eventually occurred in 90% versus 83.3%, a difference that was not statistically significant. The study was non-randomized (PMID 30569789).
  • The comparison the market makes is not the comparison that was studied. In that trial the gonadorelin arm was a pump delivering pulses through the day; the injection schedules discussed in clinic and community sources are a different exposure pattern applied to a molecule whose effect is frequency-dependent by definition.
  • Absence, stated as a finding rather than a count: searching PubMed titles and abstracts for gonadorelin together with "twice weekly" or "three times weekly" returns no records, and gonadorelin (or "native GnRH") together with "intermittent" and "subcutaneous" returns none. Records pairing gonadorelin with testosterone in title or abstract number 24, and reading them shows the majority are veterinary — tambaqui, tomcats, stallions, dogs — with the remainder covering congenital hypogonadotropic hypogonadism, cryptorchidism and assay work. None studies gonadorelin as an adjunct to testosterone therapy in men.
  • Registry status, read rather than counted: ClinicalTrials.gov entries whose intervention is actually named gonadorelin are a diagnostic-test comparison in 46 girls (NCT01278290, completed), a reproductive-hormone study in 62 adults with obesity (NCT01457703, completed), a pulsatile-pump versus hCG study in 76 participants whose status is listed as unknown (NCT02310074), and a pharmacokinetic study of the Lutrepulse product that was withdrawn with zero enrolment (NCT07152730, Ferring). No registered trial tests intermittent subcutaneous gonadorelin alongside testosterone therapy.
  • Regulatory record, from Drugs@FDA: gonadorelin has had two approved US human products and both are listed as Discontinued. Factrel (NDA 018123, gonadorelin hydrochloride) was supplied as 100, 200 and 500 mcg vials; the Lutrepulse Kit (NDA 019687, gonadorelin acetate) was supplied as 0.8 mg and 3.2 mg vials for pump delivery.
  • What still has a live US label is veterinary. DailyMed publishes five gonadorelin labels — Factrel (Zoetis), Cystorelin (Boehringer Ingelheim), Fertagyl (Merck Animal Health), GonaBreed (Parnell) and OvaCyst (Bimeda) — all for cattle. The brand name Factrel therefore now belongs to a cattle product while the human product of the same name is discontinued, which is a trap worth naming: a label found under that name is not the human one.
  • Supply route, from the FDA National Drug Code directory: 13 gonadorelin listings, every one of them a bulk ingredient registration by an API manufacturer, one of which is categorized as a bulk ingredient for human prescription compounding. There is no finished human dosage form in the directory.
  • Why the hCG comparison exists at all: FDA's notice on changes affecting compounding as of 23 March 2020 states that products transitioning to regulation as biological products are not eligible for the compounding exemptions under sections 503A and 503B, and names human chorionic gonadotropin among the bulk substances outsourcing facilities had reported using. The demand for a substitute is a regulatory event, not a finding about the molecule.
  • Research-use framing: nothing on this page is an approved indication, a protocol, or a recommendation. Material sold for research is not a pharmacy product and is not intended for human or veterinary administration.

Research timeline

Dated milestones taken from the primary records: the molecule's discovery, its first registered human study, the trials that shaped the evidence and the regulatory decisions. Each entry links to the record it comes from.

  1. Andrew Schally's laboratory proposes the amino acid sequence of the porcine hormone that releases both LH and FSH: a decapeptide, the molecule gonadorelin later reproduces. PMID 4936338
  2. Roger Guillemin's group establishes the structure of the sheep hormone independently, finds it identical to the pig sequence, and shows that the fully synthetic decapeptide has the same biological activity as the natural one. PMID 4550508
  3. Guillemin and Schally share half of the Nobel Prize in Physiology or Medicine "for their discoveries concerning the peptide hormone production of the brain". nobelprize.org · Medicine 1977
  4. Ernst Knobil's monkey experiments show that the pattern matters more than the amount: a constant infusion of synthetic GnRH fails to restore pituitary hormone release, hourly pulses restore it, and switching back to continuous delivery shuts it down again. PMID 100883
  5. Pulses of the synthetic hormone every 90 minutes normalise gonadotropin levels in five women with hypothalamic amenorrhoea, and most go on to an LH surge or ovulation: among the first reports of pulsatile treatment in humans. PMID 6998384
  6. FDA approves Factrel (gonadorelin hydrochloride) as a new molecular entity; Drugs@FDA now lists the human product as discontinued, and the brand name today belongs to a cattle product. FDA · NDA 018123
  7. A New England Journal of Medicine study gives six men with idiopathic hypogonadotropic hypogonadism the hormone in pulses from a portable pump: testosterone and gonadotropins reach the adult range, and sperm production begins in three of them within 43 weeks. PMID 6813732
  8. FDA approves the Lutrepulse Kit (gonadorelin acetate, Ferring) for delivery by pump; like Factrel, it is now listed in Drugs@FDA as discontinued, leaving no human gonadorelin product on the US market. FDA · NDA 019687

Records checked Oct 3, 2026

Claims at a glance

The claims most often made about this compound, each with the strongest kind of evidence we found for it. The grade says what was studied, not whether the claim is true; the line beside it says what that study showed.

  • Keeps the testes working in men on testosterone therapyNo study found. A PubMed title and abstract search pairing gonadorelin with testosterone therapy returned one record, which does not study the question; no registered trial enrols men on testosterone. PubMed search, Oct 6, 2026
  • Restores sperm productionHuman, non-randomised. In 45 men born unable to make GnRH, pump therapy over about 19 months brought sperm into the semen of 33; there was no control group. PMID 39210488
  • Works better than hCG for male fertilityHuman, non-randomised. One non-randomised comparison of 10 pump-treated men with 18 on gonadotropins found sperm appeared sooner, in men with a congenital deficiency only. PMID 30569789
  • Triggers ovulationHuman, non-randomised. In a 1990 multicentre trial of 109 women with hypothalamic amenorrhoea, pulsed intravenous gonadorelin led to ovulation in 91–96%; 12% of pregnancies were multiple. PMID 2122733
  • Strengthens bonesHuman, non-randomised. In 22 young men with hypogonadotropic hypogonadism, bone density rose at spine and hip after six months; untreated healthy men served only as a baseline comparison. PMID 26417369
  • Avoids oestrogen-related side effectsHuman, non-randomised. The largest cohort recorded breast enlargement (gynaecomastia) in 8 of 45 men on long-term therapy, plus 6 skin indurations and 3 allergic reactions. PMID 39210488

The reasoning behind each grade, study by study, is in this guide's Benefit & Outcome Review.

Grades checked Oct 6, 2026

A printable reference sheet with the compound's key facts, storage guidance and a vial record comes with All-Access Lifetime.

Half-life & pharmacokinetics

The figure previously published on this page — roughly 2 to 10 minutes distribution and 10 to 40 minutes terminal — is withdrawn, because it does not match either human measurement we can open. The intravenous tracer study (radioiodinated LH-RH, three male volunteers, PMID 4577100) needed a three-term exponential to describe the disappearance curve, with half-times of 2 to 4 minutes, 30 to 55 minutes, and a third component beginning beyond 10 hours; the initial distribution space was 3 to 4.7 L, approximating plasma volume. A radioimmunoassay study of immunoreactive LH-RH in plasma reports disappearance half-times of 4 to 6 minutes, with 0.2 to 0.4% of the injected dose recovered in urine within an hour (PMID 1100364). Those two methods measure different things — a radioiodine label follows fragments as well as intact peptide, which is the most likely reason the tracer study sees slow components the immunoassay does not — so the defensible statement is that the fast phase is a few minutes in both, and the longer components come from tracer data and should be read with that caveat. What survives either way is the practical consequence: the molecule is cleared on the scale of minutes, which is why the protocols that work are defined by their interval.

Reported side effects & toxicology

Reported effects in clinical use include injection-site reactions, headache, flushing, nausea and lightheadedness, with rare hypersensitivity; pump use adds the possibility of local infection or irritation at the infusion site, and the comparative trial noted skin erythema in the pump group and more facial acne and breast tenderness in the gonadotropin comparison arm (PMID 30569789). The distinctive risk described for this molecule is not an adverse effect in the usual sense but a pharmacological one: exposure that is too frequent or effectively continuous downregulates the GnRH receptor and suppresses the gonadotropins it is intended to raise, which is the mechanism the long-acting analogs are prescribed for. Long-term safety data outside the studied patient groups is limited. This is a summary of reported findings, not a complete safety profile.

Storage & handling

  • Lyophilized (powder): commonly handled refrigerated at 2-8 C and protected from light. Chemistry supports the caution — a degradation-kinetics study of gonadorelin in aqueous solution found the molecule most stable at pH 5-5.5, with degradation following Arrhenius behaviour and unaffected by acetate, phosphate, borate or carbonate buffer concentration (PMID 8897270).
  • Reconstituted (in bacteriostatic water): refrigerate at 2-8 C, protect from light, and discard if cloudy or discolored. The nearest thing to a labelled in-use period for this molecule is on a veterinary label: the Factrel (Zoetis) cattle product, which carries 2% benzyl alcohol as a preservative, directs storage at 2-8 C and says to use contents within 1 month of first vial puncture.
  • That label is a useful illustration of a point our bacteriostatic water pages make: the familiar 28-day after-entry window is compendial, from USP <797>, and applies unless the manufacturer's own labeling specifies otherwise. A vial that prints its own period governs, and this one does.

References

Compiled from primary records opened for this page: PubChem CID 638793 for identity; Drugs@FDA for NDA 018123 (Factrel) and NDA 019687 (Lutrepulse Kit); DailyMed for the five currently published gonadorelin labels and the Factrel (Zoetis, NADA 139-237) storage and preservative statements; the FDA National Drug Code directory for gonadorelin bulk-ingredient listings; FDA's notice on changes affecting compounding as of 23 March 2020; ClinicalTrials.gov records NCT01278290, NCT01457703, NCT02310074 and NCT07152730; and PubMed records 4577100, 1100364, 8897270, 9174849, 30569789, 39210488 and 40099791. Provided for educational purposes only and not as medical advice.

Guide FAQ

Quick answers about guide scope, access, and educational use context.

Is gonadorelin the same as GnRH?

Yes. Gonadorelin is a synthetic decapeptide with the identical sequence to endogenous gonadotropin-releasing hormone — pGlu-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-Gly-NH2, PubChem CID 638793, C55H75N17O13, 1182.3 g/mol, CAS 33515-09-2. That distinguishes it from the GnRH analogs (leuprorelin, goserelin, triptorelin, nafarelin), which are modified to last far longer and are used to suppress the axis rather than stimulate it. This is educational information, not medical advice.

What is gonadorelin's half-life?

Measured in humans, the fast phase is a few minutes: a radioiodinated tracer study in three male volunteers fitted three exponentials with half-times of 2-4 minutes, 30-55 minutes and a third component beyond 10 hours (PMID 4577100), while a radioimmunoassay study reports disappearance half-times of 4-6 minutes (PMID 1100364). The two methods disagree in the way you would expect, since a radioiodine label follows fragments as well as intact peptide. An earlier version of this page stated roughly 2-10 minutes distribution and 10-40 minutes terminal; that figure matched neither measurement and has been withdrawn.

How does gonadorelin compare with hCG?

They act at different points: hCG mimics LH at the gonad, while gonadorelin acts upstream at the pituitary so the body releases its own LH and FSH. One published study compares them directly — 28 azoospermic men with congenital hypogonadotropic hypogonadism, 10 on a pulsatile gonadorelin pump and 18 on cyclical hCG/hMG, with median time to spermatogenesis of 6 versus 14 months and no significant difference in whether it eventually occurred (PMID 30569789). The important qualifier is that the gonadorelin arm was a pump firing every 90 minutes, not an injection two or three times a week.

Why does dosing frequency matter more than the amount?

Because the receptor responds to the pattern. Pulsed delivery that mimics natural hypothalamic secretion sustains LH and FSH output; continuous or near-continuous exposure downregulates and desensitizes the GnRH receptor and suppresses them instead. That is not a side effect but the basis of an entire drug class: the long-acting GnRH analogs are prescribed precisely to produce the suppressed state. With a molecule cleared in minutes, the interval between exposures is what determines which of the two states you are in.

Has anyone studied gonadorelin injected two or three times a week?

Not in the indexed literature. A PubMed title and abstract search pairing gonadorelin with "twice weekly" or "three times weekly" returns no records, and pairing it with "intermittent" and "subcutaneous" returns none either. Every published human protocol we could open delivered it by pump at 5-20 mcg per pulse every 90 minutes. That is a statement about what has been published, not a claim that the schedule does or does not work.

Is gonadorelin FDA-approved?

Not currently, for humans. Drugs@FDA lists two approved US human products, both Discontinued: Factrel (NDA 018123, gonadorelin hydrochloride, 100/200/500 mcg vials) and the Lutrepulse Kit (NDA 019687, gonadorelin acetate, 0.8 mg and 3.2 mg vials). The gonadorelin labels currently published in DailyMed — Factrel, Cystorelin, Fertagyl, GonaBreed and OvaCyst — are all cattle products.

Why do clinics talk about gonadorelin as an hCG alternative?

The trigger was regulatory rather than scientific. FDA's notice on changes affecting compounding as of 23 March 2020 states that products transitioning to regulation as biological products are not eligible for the compounding exemptions under sections 503A and 503B, and names human chorionic gonadotropin among the bulk substances outsourcing facilities had reported using. Substitution followed the closure of a supply route; it was not prompted by a trial showing the substitute works the same way.

Is the Factrel label a human label?

The one you will find today is not. The human Factrel product (NDA 018123) is discontinued, and the label currently published under that brand name is a Zoetis cattle product, NADA 139-237, supplied at 50 mcg/mL with 2% benzyl alcohol as a preservative and dosed as 2 mL intramuscularly for follicular cysts. Same brand name, different species, and a different formulation from anything a human product would have carried.

How were the published pulse protocols delivered?

By programmable infusion pumps rather than syringes, which is how the published series achieved a pulse every 90 minutes around the clock.

How much published research is there on gonadorelin specifically?

Less than a search suggests. 295 PubMed records name gonadorelin in the title or abstract; the broader indexed query returns 43,233 because it sweeps in the whole GnRH and GnRH-analog literature, most of which is about other molecules. Reading the genuine set shows a large share is veterinary — cattle reproduction, companion animals, aquaculture — which is consistent with the fact that every currently labelled US gonadorelin product is a cattle product.

How should it be stored once reconstituted?

Refrigerated at 2-8 C, protected from light, and discarded if it becomes cloudy or discolored. For an in-use window, the only labelled figure that exists for this molecule is veterinary: the Factrel cattle label says to use contents within 1 month of first vial puncture. That is a manufacturer specifying its own period, which is the carve-out in USP <797> — the widely quoted 28-day after-entry limit applies unless the labeling says otherwise.

Is gonadorelin banned in sport?

Gonadotrophin-releasing hormones are covered by the WADA Prohibited List, which is reissued every January. Rather than repeat a summary that may be a revision out of date, anyone subject to anti-doping rules should check gonadorelin's current entry in GlobalDRO, the official lookup, before any decision.

Compliance and trust notes

  • Educational content only; no personalized health or outcome claims.
  • No personalized use recommendation outputs.
  • Use this material for general learning and research-context literacy.
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Reading a Gonadorelin certificate of analysis

A certificate of analysis (COA) is a laboratory’s report on one sample of one batch. The single most useful thing to know about it is that purity and identity are two separate results that fail in different ways. A high purity figure says the sample was mostly one substance; it does not say that substance was Gonadorelin. Identity — normally a mass-spectrometry result matching the expected molecular weight — is what establishes what the material actually is, and a certificate reporting purity alone has not answered that question.

Two further limits are worth holding onto. Mass per vial is its own test: a vial can be 99% pure and still contain less material than the label claims. And sterility, endotoxin, heavy metals and residual solvent screening are separately commissioned tests, usually priced individually — so a “third-party tested” badge asserts none of them unless the certificate names them. Check that the batch or lot number on the document matches the vial in front of you; an unmatched certificate describes someone else’s material.

Medibact does not test, endorse or resell peptides, and publishes no rating of any laboratory. How to read a peptide certificate of analysis walks through the document section by section, and what each COA field establishes covers the field-by-field detail and the laboratories that publish their methods.

You’ll need bacteriostatic water

The diluent for reconstituting Gonadorelin

Reconstitution is volume arithmetic — it assumes a lyophilized vial is dissolved in bacteriostatic water, which is sterile water preserved with 0.9% benzyl alcohol. The preservative is what allows a vial to be entered more than once; plain sterile water carries none and is single-entry by design. Medibact supplies USP-grade Bacteriostatic Water for Injection in a 30 mL multi-dose vial, made in the United States and shipped from the United States, for research use only. One 30 mL vial covers 30 reconstitutions at 1 mL each, 15 at 2 mL, or 10 at 3 mL — division only, not a dosing recommendation.

Bacteriostatic Water — 30 mLCompare all options

New to reconstitution? Read how to reconstitute peptides or bacteriostatic water vs sterile water. Medibact does not sell peptides.

Educational use only — not medical advice. This guide summarizes information reported in published research and community practice for educational purposes. It is not medical advice and not a recommendation to use any compound. Any doses, schedules, or combinations shown are examples of what has been reported, not instructions for you. Many peptides described here are research compounds that are not FDA-approved for the uses discussed and may be investigational or restricted. Effects, risks, and legal status vary; individual needs and results vary. Consult a qualified, licensed healthcare professional before making any decision. Do not use this content to diagnose, treat, or dose yourself.