Gonadorelin
GnRH · LHRH · Factrel (brand) · Luteinising hormone-releasing hormone
Gonadorelin is not an analogue of anything. It is the identical ten-amino-acid sequence of human gonadotropin-releasing hormone, the signal the hypothalamus sends to the pituitary to release LH and FSH. It has held FDA approval as a diagnostic agent — used to test whether a pituitary responds — and it is approved in veterinary medicine for reproductive management.
It has become widely used for a purpose it was never approved or studied for: maintaining testicular function during testosterone replacement therapy. The reasoning is straightforward. Exogenous testosterone suppresses the body's own LH signal, the testes shrink and stop producing sperm, and supplying a GnRH pulse should keep that pathway alive. Many clinicians prescribe it for exactly this, having moved away from hCG when that became harder to obtain.
The rationale is sound and the evidence for it in this specific use is thin. What has actually been studied is hCG, which acts further down the chain at the testis. Gonadorelin acts at the pituitary, which means it can only work if the pituitary is still responsive. There is a further complication that matters here: continuous exposure to GnRH suppresses the axis instead of stimulating it. That is not a theoretical risk; it is the established mechanism of prostate cancer treatment.
How it works
Gonadorelin binds GnRH receptors on pituitary gonadotroph cells, causing release of LH and FSH. LH drives testosterone production in the testis, and FSH drives sperm production. It is the natural signal, not a modified version of it.
Pulsatility is everything with this molecule, and it is the reason two opposite clinical uses exist. Delivered in pulses, as the hypothalamus does naturally, it stimulates the axis. Delivered continuously, it downregulates the receptors and shuts the axis down. That is precisely how GnRH agonists achieve chemical castration in prostate cancer treatment.
Its half-life is a few minutes. Which is what allows intermittent injection to approximate a pulse. It is also why the interval between injections is the variable that decides whether you are stimulating or suppressing, and why frequent dosing is not obviously the cautious choice.
Compared with hCG, which mimics LH directly at the testis, gonadorelin acts one step earlier. That preserves more of the natural feedback loop in principle, and it also means it does nothing if the pituitary itself is unresponsive.
Regulatory status — United States
Approved by the FDA as a diagnostic agent for evaluating pituitary gonadotropin function, and approved in veterinary reproductive medicine. Not approved for use alongside testosterone replacement therapy, though it is commonly prescribed off-label and compounded for that purpose. Material sold as a research chemical is not a compounded prescription product.
Last reviewed 16 Aug 2026. Regulatory positions in this category change frequently; we date this line so you can see how current it is.
What it is studied for
Each entry states the evidence behind it. We do not rank indications by effectiveness — for most compounds here, that would be a claim nobody can support.
Testing pituitary gonadotropin function
Clinical trialThe approved human use.
EvidenceApproved as a diagnostic agent, with LH measured after a single dose to establish whether the pituitary responds.
Maintaining testicular function during testosterone therapy
Community practiceThe common off-label use, and the reason it is bought.
EvidenceNo controlled trial has studied gonadorelin for this. The evidence in this setting is for hCG, a different molecule acting at a different point in the cascade.
Restoring fertility after anabolic steroid use
Community practiceDescribed in the same context.
EvidenceRecovery protocols have been studied with hCG and selective oestrogen receptor modulators. Gonadorelin has not been studied for this purpose.
Identity and clearance
Molecule
- Class
- Gonadotropin-releasing hormone, identical to the human sequence
- Molecular weight
- 1182.3 Da
- Length
- 10 amino acids
Sequence
Pyr-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-Gly-NH2
Pharmacokinetics
Clinical trialA half-life of around four minutes. The LH response peaks within about 30 minutes and is over within hours. That is why dosing frequency — not dose size — is the variable that matters here.
Dose protocols reported in sources
Displayed for reference only. Every row says where it came from, and a trial protocol and a community convention are not the same kind of information. None of this is fed into the calculator, and none of it is a recommendation.
| Goal | Dose | Frequency | Route | Units, 2 mg vial | Source | Start this protocol |
|---|---|---|---|---|---|---|
| Diagnostic test, the approved use | 100 mcg | A single dose, once | Subcutaneous100 mcg with LH and FSH sampled over the following two hours. This is a test of pituitary responsiveness, not a treatment. | 10 u | Clinical trial | Start this |
| Commonly prescribed alongside testosterone therapy | 100 mcg – 200 mcg | Two to three times weekly, or on the same schedule as testosterone | SubcutaneousThe figures most often described in compounded prescriptions and community practice. No trial has established either the dose or the interval for this use, and the interval is the variable that determines whether the axis is stimulated or suppressed. | 10–20 u | Community practice | Start this |
Start this copies a row into a protocol of your own, which you can then edit. Where a source gave a dose range or an ambiguous frequency, those fields arrive empty — we will not pick a number on your behalf.
CheckRows marked community practice describe what people commonly do, drawn from public discussion. They are not derived from any trial and are not evidence that a dose is safe or effective.
Calculator
Work out what to draw
Pre-filled with a 2 mg vial as a worked example. These are not recommended values — change them to match the vial in front of you.
Draw to 10 units on a 1 mL U-100 syringe. That is 0.1 mL, containing 100 mcg of Gonadorelin.
10 units sits exactly on a printed line.
Bioalmanac performs arithmetic on values you enter. It does not recommend doses, schedules or compounds, and nothing here is medical advice. Confirm every calculation against your vial and syringe before drawing, and speak with a licensed healthcare provider.
Open this calculation in the full calculator
Units, concentration, bacteriostatic water — the glossary defines the vocabulary, and a unit is not a fixed volume.
Safety
Reported effects
- Generally well tolerated in diagnostic useClinical trial
Established
The approved use is a single dose. That tolerability record does not extend to repeated dosing over months.
- Headache, flushing and nauseaClinical trial
Occasionally reported
- Injection site reactionsCommunity practice
Commonly reported
- Suppression of the axis with too-frequent dosingPublished review
Mechanistically established
The opposite of the intended effect, and not a rare idiosyncrasy. Continuous GnRH exposure downregulating the receptor is the basis of prostate cancer treatment. It would present as worsening rather than improving testicular function.
- Whether it preserves fertility as intendedCommunity practice
Unstudied
No trial has measured sperm parameters or testicular volume on gonadorelin alongside testosterone therapy. The rationale is mechanistic.
When to stop
- Testicular shrinkage that continues or worsens. That is the outcome it is meant to prevent, and a sign the schedule may be suppressing rather than stimulating.
- Falling libido or morning erections beyond what the testosterone protocol explains.
- Any allergic response: rash, hives, facial swelling or difficulty breathing. Seek urgent care.
- Persistent headache, flushing or nausea after dosing.
Interactions and situations that need care
- Hormone-sensitive cancer, including prostate and breastAvoid
Stimulating the axis raises testosterone and oestrogen, which are the growth signals these cancers depend on. The irony that continuous GnRH is used to treat prostate cancer does not make intermittent GnRH safe there. It makes the dosing interval the difference between two opposite effects.
- Using it in place of medical supervision on testosterone therapyUse caution
Testosterone therapy needs monitoring of haematocrit, oestradiol, PSA and lipids regardless of what else is added. Adding an unstudied peptide to an unmonitored protocol compounds the problem rather than mitigating it.
- Pregnancy and breastfeedingAvoid
Manipulating the reproductive axis during pregnancy has no justification and no safety data.
- Competing in a tested sportAvoid
Gonadotrophin-releasing factors are prohibited for male athletes at all times under WADA's S2 category, alongside hCG and LH.
SportProhibited by the World Anti-Doping Agency under S2: Peptide Hormones, Growth Factors, Related Substances, gonadotrophin-releasing factors, at all times, for male athletes. Gonadotrophin-releasing factors are prohibited for males at all times. hCG and LH are named in the same section.
What to expect
HonestlyThere is no human efficacy data for this compound, so there is no evidence-based timeline to give. Any site publishing a week-by-week schedule of expected effects has invented it.
- It reliably produces an LH rise from a single dose. That is established and it is the approved diagnostic use.
- Whether it preserves testicular function during testosterone therapy has never been studied. The evidence in that setting belongs to hCG, a different molecule acting at a different point.
- Dosing frequency decides the direction of the effect. Too frequent moves toward the continuous exposure that suppresses the axis, so more is not safer here.
- It only works if your pituitary responds. hCG acts directly at the testis and does not have that requirement.
- It is prescribed off-label by many clinicians. That is a reasonable clinical judgement about a sound rationale, not a substitute for trial evidence.
Storage and handling
- Freeze-dried powder
- Refrigerated at 2–8 °C, protected from light.
- After mixing
- Refrigerated at 2–8 °C. Do not freeze once mixed. Bacteriostatic water is preferable given the multi-week dosing pattern.
- Long-term, frozen
- Unopened powder is stable at −20 °C or colder.
With other peptides
- HCGcaution
Both are used to keep the gonadal axis running during testosterone therapy, at different points. This acts on the pituitary; hCG bypasses it and acts on the testes. Using both is redundant rather than additive.
- Testosterone (TRT)synergistic
Prescribed alongside testosterone to preserve the pituitary signal it suppresses. Which of this and hCG suits depends on where the suppression sits, which is a clinical question.
Checking your vial
Research chemicals carry no manufacturing standard, so what the vial looks like is often the only quality signal available before you use it. More on assessing quality and COAs.
White cake, clear solution
Standard for a short peptide.
Collapsed cake or cloudy solution
Heat damage or degradation. Do not use it.
Questions
- Is gonadorelin better than hCG for preserving fertility on TRT?
- Nobody knows, because it has not been studied for that. hCG has the evidence. The argument for gonadorelin is that acting at the pituitary preserves more of the natural loop. A reasonable mechanistic case, and a case, not a finding.
- How often should I inject it?
- No trial establishes this, and it is the question that matters most with this compound. Frequency determines whether you stimulate or suppress the axis, because continuous GnRH exposure downregulates the receptor. That makes it a question for a prescriber who can measure the result, not one to resolve by increasing the dose.
- Why is a natural hormone only approved as a diagnostic?
- Because its four-minute half-life makes it impractical as a treatment. Sustained therapy needs either a pump delivering genuine pulses or a long-acting analogue. The long-acting analogues suppress the axis, which is what they are used for.
References
Gonadorelin as a diagnostic agent for pituitary gonadotropin function
FDA prescribing information and supporting clinical literature, 2015 · Regulatory labelling based on clinical data
Humans · 100 mcg, single dose · Single administration with sampling over 2 hours
Produces a reliable, measurable LH and FSH response, supporting approval as a test of pituitary gonadotroph function. Well tolerated in single-dose use, with headache, flushing and nausea occasionally reported.
Pulsatile versus continuous GnRH exposure: stimulation and desensitisation of the gonadal axis
Reproductive endocrinology review literature, 2016 · Review
Humans
Establishes that pulsatile GnRH stimulates gonadotropin release while continuous exposure downregulates the receptor and suppresses the axis, the mechanistic basis for using GnRH agonists to suppress testosterone in prostate cancer.
Commonly described protocols alongside testosterone therapy
Bioalmanac editorial summary of public sources and compounded prescribing patterns, 2026 · Not a study
Records the doses and intervals described in community discussion and in compounded prescriptions. No trial has studied gonadorelin in this setting, and these carry no evidential weight about safety or effect.
Related compounds
HCG
An approved fertility medicine that mimics LH. Widely used to keep the testes working during testosterone therapy. Also sold, separately, for a weight-loss diet the FDA has said outright does not work.
Testosterone (TRT)
Not a peptide, and the most consequential thing on this site. Approved replacement therapy for diagnosed hypogonadism — a Schedule III controlled substance — and something that will make you infertile while you take it.
Ipamorelin
A selective growth hormone secretagogue that prompts a short pulse of GH release. Widely used, and supported almost entirely by early pharmacology rather than outcome trials.
CJC-1295
A GHRH analogue that raises growth hormone by amplifying the body's own release signal. Sold in two forms whose durations differ by two orders of magnitude.
Next
What to do with Gonadorelin
- Keep a record of itTurn a dose and a schedule into a protocol, then log what you actually take. Gonadorelin is filled in for you.
- See what it costsPer-milligram prices read from vendor sites and confirmed by a person, so vial sizes compare.
- Check a combinationWhat our profiles record about Gonadorelin alongside each other compound — including the pairs where nothing is recorded.
Keep this page honest
If something here is wrong, out of date, or missing a source, tell us and we will fix it and say that we did.
This page is educational. It describes what published research reports, not what you should do. Peptides discussed here are largely not approved for human use, and nothing on Bioalmanac is medical advice. No clinician reviews these pages.
Page last updated 16 Aug 2026