GnRH, LHRH, gonadorelin acetate or hydrochloride; formerly Factrel and Lutrepulse in the US
The ten-amino-acid hormone the hypothalamus releases in pulses to tell the pituitary to make LH and FSH, which in turn drive the testes or ovaries. Given in pulses it stimulates; given continuously it does the opposite and shuts the pituitary down.
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Gonadorelin is identical to GnRH, the brain hormone that controls reproduction. It binds GnRH receptors on the pituitary gland at the base of the brain, which then makes and releases LH and FSH, the hormones that drive the testes and ovaries. Half of a dose is broken down in the blood within about 4 minutes, so each injection acts as a short pulse. In monkeys unable to make GnRH, hourly pulses restored LH and FSH release, but a steady infusion did not.
LabelBased on the product label.
Outside pump therapy, no trial has tested whether a few injections a week, each acting for minutes, keep the testes working during testosterone therapy.
UK gonadorelin SmPC
Diagnostic test: a single 100 mcg dose under the skin or into a vein, with LH measured before the dose and at 15, 30, 45, 60 and 120 minutes.
Mao 2016
Pulsatile pump: 10 mcg under the skin every 90 minutes, adjusted to keep LH and FSH in range; ovulation-induction practice uses about 5–20 mcg per pulse every 60–120 minutes.
100–200 mcg under the skin, 2–3× weekly alongside testosterone therapy; some guides argue the short half-life makes daily dosing the minimum.
Continuous, shown over 26 weeks
The ways Gonadorelin is most often run, each tagged with where it comes from.
The approved use: it shows whether the pituitary can still respond. It says nothing about whether repeated dosing helps anything.
For men whose own GnRH is missing. First sperm appeared at a median of 6 months, against 18 months on hCG plus hMG (Mao 2016).
Ovulation in 96% of cycles and one follicle only in 75%, with twins in 1.6% — fewer multiples than injected gonadotropins (Quaas 2022).
Took the place of hCG for many users after hCG became a biologic in 2020 and could no longer be compounded. Never tested in a trial for this use.
Under the skin of the belly or thigh, rotating sites (community). Approved use is one injection under the skin or into a vein, a pump that delivers small pulses, or a nasal spray sold in parts of Europe.
The approved label covers a single diagnostic dose, so it gives no missed-dose rule. Skip it and resume the usual schedule; don’t double up, since bunched doses push toward suppression rather than stimulation.
LH rises and peaks. This is the whole basis of the diagnostic test.
LabelIn men with no GnRH of their own, first sperm at a median of 6 months versus 18 months on hCG plus hMG; testicles grew faster too, though testosterone ran lower (8.3 vs 16.2 nmol/L).
TrialOvulation in 96% of cycles, live birth in 65.9% of treatment courses in a 25-year single-center series of 66 women.
TrialUsers describe testicular fullness returning. Whether LH, FSH and intratesticular testosterone actually hold up on a twice-weekly schedule has not been measured.
CommunityInjection-site hardening, pain or swelling (label: rare for the single dose; common with pumps)
Rotate sites. In the pump studies, allergic redness at the site was the main complaint.
Headache, dizziness (label: rare)
Usually mild and brief. Tell the prescriber if it persists.
Nausea or belly discomfort (label: rare)
Reported more at higher amounts; splitting the dose is the usual community answer.
Hypersensitivity reactions, including bronchospasm (label: rare)
The label says to watch anyone who gets a repeat dose, especially into a vein.
Antibodies against the peptide (label: rare)
Reported with longer use. It can blunt the response over time.
Get medical help for hives, swelling of the face or throat or trouble breathing, wheezing, or a hot, spreading red injection site with fever. A sudden severe headache with vomiting or a change in vision needs emergency care.
What its label rules out or warns about, most important first.
Only interactions stated on a product label or measured in a human study are listed.
Label: a product label rules it out, warns about it or lists the interaction. This isn’t a complete list: a pharmacist or doctor can check a specific medicine or condition.
The drug it is used in place of. hCG acts directly on the testes, gonadorelin one step earlier at the pituitary. Some guides run both; the combination has not been tested.
Acts one step earlier still, on the neurons that release GnRH. Sold as a fertility pairing, with no trial behind the combination.
4 key published human studies, with how many people took part. Animal studies aren’t listed here.
First sperm at a median of 6 months on the pump versus 18 months on hCG/hMG (p<0.001); testicles reached each size target sooner, while testosterone ran lower (8.3 vs 16.2 nmol/L).
Mao et al., Asian J Androl 2017, PMID 28051040
Ovulation in 96% of cycles, a single follicle in 75%, clinical pregnancy in 74.4% and live birth in 65.9% per course, with one twin pregnancy (1.6%).
Quaas et al., J Assist Reprod Genet 2022, PMID 36378460
GnRH gave earlier sperm appearance (5.3 months sooner, p=0.004) and larger testicles, with no significant difference in sperm detection, sperm count or pregnancy rate; allergic reactions were commoner on GnRH, gynecomastia and acne on gonadotropins.
Wei et al., World J Mens Health 2020, PMID 32777865
Sperm appeared at a median of 6 months on the pump versus 14 months on hCG/hMG (p=0.01); 90% versus 83.3% produced sperm. Allergic redness at the infusion site was the pump’s common side effect.
Zhang et al., Am J Mens Health 2018, PMID 30569789
The UK label covers only a single diagnostic dose. Treatment evidence comes from pump studies in people whose brains make too little GnRH, mostly non-randomized, plus a pooled analysis of 7 comparative studies in 420 men. No controlled trial has tested a few injections a week, use alongside testosterone therapy, or the long-term safety of repeated injections.
| Vial | Water | Common dose | Draw | Strength | Action |
|---|---|---|---|---|---|
| 2 mg | 2 mL | 100 mcg | 10 units (0.10 mL) | 1 mg/mL | |
| 5 mg | 2.5 mL | 100 mcg | 5 units (0.05 mL) | 2 mg/mL |
Bacteriostatic water. A 2 mg vial in 2 mL gives 1 mg/mL, so 100 mcg is 10 units on a U-100 syringe. The approved 100 mcg diagnostic vial is different: it is mixed with 1 mL of sterile water, used at once, and any remainder discarded.
Syringe units for common doses at different water volumes. Select a cell to open it in the calculator.
| Dose | Water added | ||
|---|---|---|---|
| 1 mL | 2 mL | 3 mL | |
| 50 mcg | |||
| 60 mcg | |||
| 75 mcg | |||
| 100 mcg | |||
| 150 mcg | |||
| 200 mcg | |||
U-100 insulin syringe: 100 units is 1 mL. Draws over 100 units show in mL. Faded values are under 2 units, which is hard to measure. Check that your vial holds the larger volumes.
Every compound side by side: the half-life chart and the storage chart.
The ten-amino-acid hormone the hypothalamus releases in pulses to tell the pituitary to make LH and FSH, which in turn drive the testes or ovaries. Given in pulses it stimulates; given continuously it does the opposite and shuts the pituitary down.
Gonadorelin is identical to GnRH, the brain hormone that controls reproduction. It binds GnRH receptors on the pituitary gland at the base of the brain, which then makes and releases LH and FSH, the hormones that drive the testes and ovaries. Half of a dose is broken down in the blood within about 4 minutes, so each injection acts as a short pulse. In monkeys unable to make GnRH, hourly pulses restored LH and FSH release, but a steady infusion did not. Outside pump therapy, no trial has tested whether a few injections a week, each acting for minutes, keep the testes working during testosterone therapy.
No gonadorelin medicine is approved and marketed in the US today. Factrel (gonadorelin hydrochloride, approved September 1982) and Lutrepulse (gonadorelin acetate, approved October 1989) are both listed as discontinued in FDA’s database, and the Factrel, Cystorelin, Fertagyl, OvaCyst and GonaBreed labels on DailyMed now are animal drugs, not human medicines. In Europe it is still authorized: Lutrelef for pump therapy (France, Austria, Netherlands), the nasal spray Kryptocur (Germany, Austria, Italy) and a 100 mcg diagnostic injection in the UK. Gonadorelin acetate sits in Category 1 on FDA’s 503B list for outsourcing facilities (updated March 21, 2025), marked as a component of an approved drug. It is in no category on the 503A list; pharmacies compound it under 503A because gonadorelin acetate has a USP monograph, not through the bulks list. Compounded gonadorelin is not an FDA-approved product.
From the label (UK gonadorelin SmPC): Diagnostic test: a single 100 mcg dose under the skin or into a vein, with LH measured before the dose and at 15, 30, 45, 60 and 120 minutes. From human studies (Mao 2016): Pulsatile pump: 10 mcg under the skin every 90 minutes, adjusted to keep LH and FSH in range; ovulation-induction practice uses about 5–20 mcg per pulse every 60–120 minutes. These are the amounts sources reference, not recommendations.
There’s no single right amount, because the water only sets the strength. With 2 mL of bacteriostatic water in a 2 mg vial, the strength is 1 mg/mL, so 100 mcg is 10 units on a U-100 insulin syringe. More water makes small doses easier to measure. The dose chart above shows other volumes.
Pregnancy or breastfeeding: Ruled out in known or suspected pregnancy, and the UK label says not to give it to nursing mothers. Allergy to gonadorelin: Ruled out. Rare allergic reactions, including bronchospasm (sudden narrowing of the airways), are listed; the label says to watch closely anyone given it again, especially into a vein. A pituitary tumor (adenoma): Not recommended: the label warns that bleeding and tissue death in the gland (pituitary apoplexy) can occur with gonadorelin and similar drugs. The “Who should avoid it” section lists 1 more group and 4 interactions.
About 4 minutes, according to the prescribing information. Broken down in plasma and cleared in the urine after injection.
Approved vial: store below 25 °C. Research powder: freezer for long storage, fridge for short periods (community practice). Approved vial: mix immediately before use, refrigerate and use within 1 day; discard the rest. Mixed research vials: 2–8 °C, about 4 weeks (community practice).
In some cases. S2.2.1 testosterone-stimulating peptides: gonadotropin-releasing hormone (GnRH, gonadorelin) and its agonist analogues are named, and the whole subsection applies to males only. Banned at all times in males, not prohibited for female athletes.
Yes. The human studies section lists 4 published studies. The largest, from 2020, included 420 people. GnRH gave earlier sperm appearance (5.3 months sooner, p=0.004) and larger testicles, with no significant difference in sperm detection, sperm count or pregnancy rate; allergic reactions were commoner on GnRH, gynecomastia and acne on gonadotropins.
For the protocol details
For how it works, who should avoid it and the limits of the evidence
Doses tagged Community come from public dosing guides and user reports, checked against at least two of them. Those sites aren’t named here because many of them sell peptides or earn commissions on them.