Gonadorelin
Gonadotropin-Releasing Hormone (GnRH) · GnRH · LHRH · Luteinizing Hormone-Releasing Hormone · Factrel · Lutrelef
Native GnRH decapeptide, now the usual compounded stand-in for hCG on TRT.
Typical dose
200 mcg
1-2x daily
Range
100–400
mcg
Half-life
4 min
see Dosing
Evidence
Human trials
Subcutaneous · Intramuscular · Intravenous
What it is
Gonadorelin is synthetic GnRH, identical to the hypothalamic decapeptide that drives the pituitary to release LH and FSH. It has been used clinically for decades as a diagnostic stimulation test and, delivered by pump, as genuine pulsatile therapy for men and women with hypogonadotropic hypogonadism.
In the men's health world it became common after 2020, when US compounding restrictions pushed clinics away from hCG. Gonadorelin is now widely prescribed as a compounded injection to preserve testicular function on TRT. It is important to be clear that this is an extrapolation, not a studied protocol: the human evidence supports pulsatile pump delivery every 90 to 120 minutes, not one or two subcutaneous shots a day.
It also acts one step higher in the axis than hCG. Gonadorelin needs a functioning pituitary to do anything, so if the pituitary is heavily suppressed the signal has nowhere to land. hCG bypasses that problem by acting directly on the testis, which is why hCG remains the more reliable option for testicular maintenance.
How it works
Gonadorelin binds the GnRH receptor on pituitary gonadotroph cells and triggers release of stored LH and FSH within minutes. The pituitary is exquisitely sensitive to the pattern of that signal: brief, spaced pulses keep the receptor responsive, while a continuous or too-frequent signal downregulates it and shuts gonadotropin output off entirely, which is exactly how GnRH agonists such as triptorelin and leuprolide achieve chemical castration.
With a half-life measured in minutes, a subcutaneous gonadorelin injection produces a sharp, short LH and FSH spike and then nothing. That is safe from a downregulation standpoint but it delivers a fraction of the daily gonadotropin exposure a pump would, which is the main reason its testicular effect is weaker and less predictable than hCG.
Dosing
Because the half-life is a matter of minutes, twice-weekly gonadorelin schedules some clinics prescribe deliver almost no cumulative gonadotropin exposure; daily or twice-daily is the minimum that makes mechanistic sense, and even that is far from the pulsatile pump protocol the human evidence is built on.
Reconstitution calculator
Pre-loaded with Gonadorelin’s vial size, water volume and typical dose. Change anything.
Typical: 200 mcg · range 100–400
Draw to
20 u
0.2 mL · 200 mcg
Concentration
1 mg/mL
10 mcg per unit
Doses per vial
10
Vial lasts
10 days
Draw to 20 units on the barrel.
Once mixed
Refrigerate at 2-8 °C and use within about 4 weeks in bacteriostatic water; small linear peptides like this degrade steadily once in solution and should never be frozen and thawed repeatedly.
A 2 mg vial in 2 mL of bacteriostatic water gives 1,000 mcg/mL, so 200 mcg is 0.2 mL, or 20 units on a U-100 insulin syringe. Run the water slowly down the vial wall and swirl rather than shaking.
Storage
Before mixing
Refrigerate at 2-8 °C protected from light; the lyophilised powder is stable for 2 years or more and tolerates room-temperature shipping for a few weeks.
After mixing
Refrigerate at 2-8 °C and use within about 4 weeks in bacteriostatic water; small linear peptides like this degrade steadily once in solution and should never be frozen and thawed repeatedly.
Reported benefits
- ▪Acts at the pituitary, so it raises both LH and FSH rather than LH signalling alone
- ▪Short half-life makes pituitary downregulation essentially impossible at sane doses
- ▪Widely available on prescription in the US where compounded hCG is now restricted
- ▪Less estradiol rise than hCG in practice, largely because the testicular stimulation it produces is weaker and shorter
- ▪Useful as a diagnostic tool: the LH response tells you whether the pituitary is responsive
- ▪Cheap per dose relative to hCG or hMG
Side effects
- ▪Generally well tolerated, with injection-site stinging the most common complaint
- ▪Flushing, light-headedness or headache shortly after injection in some users
- ▪Nausea and abdominal discomfort, usually mild and transient
- ▪Rare hypersensitivity and local urticaria at the injection site
- ▪Frequent or continuous dosing can paradoxically suppress LH and FSH by downregulating the receptor
- ▪Requires daily or twice-daily injections, which many people abandon
Do not use if
- ▪Known hypersensitivity to GnRH or GnRH analogues
- ▪Hormone-sensitive tumours, including prostate cancer
- ▪Pituitary adenoma or other structural pituitary disease, where the response is unpredictable
- ▪Any situation where the pituitary is known to be non-functional, since gonadorelin has no direct testicular action
Evidence level — Human trials
Controlled human clinical data exists.
Formerly FDA-approved as Factrel for diagnostic use and now supplied mainly through compounding pharmacies and research-chemical vendors, prescription-only where it remains registered.
Gonadorelin FAQ
Is gonadorelin as good as hCG for keeping my testicles working?+
There is no head-to-head evidence that it is, and mechanistically there are reasons to doubt it. hCG acts directly on the testis and stays in circulation for around a day, while a gonadorelin injection produces a spike lasting minutes and needs a responsive pituitary to work at all. Treat it as the option available to you rather than the better option.
Why do some clinics prescribe it twice a week?+
Largely because that is the schedule people were used to with hCG. Given a 4-minute half-life, a twice-weekly injection delivers two brief LH pulses per week against the roughly eight to fourteen a healthy hypothalamus drives every day. If you are going to use gonadorelin, daily or twice-daily dosing is the version that has any mechanistic logic behind it.
Can gonadorelin shut me down like triptorelin can?+
Not at normal doses and normal spacing. Downregulation requires the GnRH receptor to be occupied continuously, and gonadorelin is gone within minutes. It is the long-acting agonists such as triptorelin and leuprolide that produce castration-level suppression.
Will it work while I am on a cycle?+
Only partly. High circulating androgens and estradiol suppress the pituitary's ability to respond, so the LH release a gonadorelin dose produces is smaller than it would be off cycle. This is exactly the scenario where hCG's direct testicular action is the more dependable choice.
References
- 1.Pulsatile GnRH or human chorionic gonadotropin/human menopausal gonadotropin as effective treatment for men with hypogonadotropic hypogonadism: a review of 42 cases — European Journal of Endocrinology (1998) PMID 9758439
- 2.Pulsatile gonadotropin-releasing hormone therapy is associated with earlier spermatogenesis compared to combined gonadotropin therapy in patients with congenital hypogonadotropic hypogonadism — Asian Journal of Andrology (2017) PMID 28051040
- 3.Spermatogenesis of Male Patients with Congenital Hypogonadotropic Hypogonadism Receiving Pulsatile Gonadotropin-Releasing Hormone Therapy Versus Gonadotropin Therapy: A Systematic Review and Meta-Analysis — The World Journal of Men's Health (2021) PMID 32777865
More hpta & fertility
hCG
LH-mimic that keeps the testes producing while exogenous androgens shut the axis down.
500 IU · Every other day, or 2-3x per week
hMG
Urine-derived FSH plus LH activity, added to hCG when sperm counts will not recover.
75 IU · 3x per week
Kisspeptin-10
Upstream GnRH trigger — the switch that makes the hypothalamus fire and the pituitary release LH.
50 mcg · 3x weekly on non-consecutive days
Triptorelin
Long-acting GnRH agonist taken as one microdose to fire off a large LH and FSH surge.
100 mcg · Single one-off dose