Other compounds

Gonadorelin

Updated · 31 sources · Editorial policy

Gonadorelin is the synthetic form of gonadotropin-releasing hormone (GnRH), the 10-amino-acid peptide the hypothalamus releases to make the pituitary secrete luteinizing hormone (LH) and follicle-stimulating hormone (FSH). It is chemically identical to the natural hormone. In men, LH drives testosterone production in the testes and FSH supports sperm production.

The most important fact about gonadorelin is that timing decides what it does. Given in short pulses every 1–2 hours, it switches the reproductive axis on; given continuously, the pituitary stops responding. Two human products were FDA-approved, Factrel (1982) and Lutrepulse (1989), and both are now listed as discontinued. Gonadorelin remains approved for cattle, and for people in the US it is now available only as a compounded drug, which FDA does not review.

This page summarizes what the FDA record, clinical studies and regulators report. It is for education only and is not medical advice.

Property Detail
Drug class Synthetic hypothalamic peptide hormone (native GnRH, a decapeptide)
Formula / weight C₅₅H₇₅N₁₇O₁₃; 1182.3 g/mol (PubChem)
Former US human products Factrel (gonadorelin hydrochloride), approved September 30, 1982; Lutrepulse (gonadorelin acetate), approved October 10, 1989. Both discontinued
Route IV or subcutaneous injection; pulsatile therapy uses a portable pump
Doses in cited studies 100 µg IV bolus as a pituitary stimulation test; 2.5–10 µg per pulse every 60–120 min for pulsatile therapy
Half-life About 2–3 min after IV injection (initial phase); apparent half-time about 24 min after subcutaneous injection
Key mechanism fact Pulses stimulate LH and FSH; continuous exposure fails to, and desensitizes the pituitary
US status No marketed human product; veterinary products approved; not a DEA-controlled substance
FDA compounding Gonadorelin acetate is in category 1 (under evaluation) for 503B outsourcing facilities
WADA status Prohibited at all times in males (S2.2.1)

What it is

GnRH was isolated from pig hypothalamus, and its 10-amino-acid sequence was published by Andrew Schally’s group in 1971 (Matsuo et al., BBRC 1971). Gonadorelin is that same sequence made synthetically. It begins with a pyroglutamic acid and ends in an amidated glycine, and the veterinary Factrel label states that it has the identical sequence and physiological activity of the natural hormone (Factrel veterinary label; PubChem CID 638793).

Gonadorelin has been sold as different salts. The salt changes the weight per vial, not the active peptide.

Salt Product (US) Use
Gonadorelin hydrochloride Factrel (human, NDA 018123); Factrel (cattle, NADA 139-237) Human product discontinued; veterinary product current
Gonadorelin acetate Lutrepulse (human, NDA 019687) Pulsatile IV therapy kit; discontinued
Gonadorelin diacetate tetrahydrate Cystorelin (cattle) Veterinary

Where it sits in the hormone chain

Gonadorelin works one step below kisspeptin and one step above LH and hCG. That position explains how it differs from the related compounds in this library:

Compound Where it acts Net effect on testosterone
Kisspeptin-10 Hypothalamus: makes GnRH neurons fire Raises it only if GnRH neurons, pituitary and testes work
Gonadorelin Pituitary: replaces the GnRH signal Raises it only if given in pulses and the pituitary and testes work
hCG Testes: acts like LH directly Raises it without needing the brain or pituitary
Enclomiphene, clomiphene Hypothalamus and pituitary: block estrogen feedback Raise the body’s own GnRH, LH and FSH; taken by mouth

Pulsatile vs continuous dosing

The body releases GnRH in bursts, not as a steady stream. This turned out to be essential.

  • Monkeys (1978). In rhesus monkeys whose hypothalamus had been destroyed, hourly GnRH pulses restored LH and FSH secretion, but a constant infusion did not. Switching animals from pulses to a constant infusion shut secretion down again, which the authors called “desensitization” (Belchetz et al., Science 1978). This is animal data, but it set the template for human therapy.
  • Men (1991). In 4 men with idiopathic hypogonadotropic hypogonadism (low testosterone because the brain does not make GnRH), 10 µg every 2 hours given as pulses raised bioactive LH and FSH. The same total dose given as a continuous infusion did not, even though blood GnRH levels were similar. Testosterone did not rise significantly with either regimen over this short study (Matsumoto et al., Int J Androl 1991).
  • Women (1991). In 5 women with hypothalamic amenorrhea, all ovulated on pulsatile GnRH and none ovulated on a continuous infusion that produced similar average GnRH levels (Southworth et al., JCEM 1991).

Suppression takes time to develop. In 18 healthy men, a 3-hour continuous infusion raised LH 3–4 fold and testosterone up to 1.5 times baseline, much like pulses did over the same 3 hours (Fauser et al., Andrologia 1986).

Long-acting GnRH agonists such as leuprolide use this principle on purpose. The Lupron Depot label describes an initial rise in LH, FSH and testosterone, followed by a fall in testosterone to castrate levels (under 50 ng/dL) within two to four weeks of continuous exposure (Lupron Depot label). Native gonadorelin is cleared within minutes, so it acts like a pulse unless it is infused continuously.

Pharmacokinetics

Gonadorelin is a short peptide and is cleared very quickly.

Study Route and dose Finding
Fauconnier et al., 1978 (6 volunteers) IV bolus Half-life 2.4 ± 0.4 min (measured 3–10 min after injection)
Hurley et al., JCEM 1987 (5 women with hypothalamic amenorrhea) 10 µg IV Rapid phase half-life 2.8 min, then a slower phase of 33 min
Same study 2.5, 5 and 10 µg subcutaneous Peak at 5–10 min; mean disappearance half-time 24 min (range 18–30); under 10% of peak by 90 min

In the Hurley study, LH peaked 20–30 minutes after either route, and peak LH after 10 µg was similar IV and subcutaneously (15.2 vs 13.2 IU/L). Three subcutaneous pulses 90 minutes apart each produced an LH response, which supported subcutaneous pumps as an alternative to IV lines.

Approval history and regulatory status

Human products

Product Salt FDA application Approved Status
Factrel Gonadorelin hydrochloride, 0.1, 0.2 and 0.5 mg vials NDA 018123 (new molecular entity, priority review) September 30, 1982 Discontinued
Lutrepulse Gonadorelin acetate, 0.8 and 3.2 mg vials (kit) NDA 019687 (orphan) October 10, 1989 Discontinued

Sources: Drugs@FDA for NDA 018123 and NDA 019687. FDA does not host the labels for either product.

Factrel was made by Ayerst Laboratories, and clinicians also used it in infusion pumps for ovulation induction (Malo et al., J Reprod Med 1985). Lutrepulse was developed by Ortho Pharmaceutical as a kit for pulsatile IV therapy in women with hypothalamic amenorrhea (Santoro, AJOG 1990). Drugs@FDA now lists Hikma and Ferring as the application holders.

Veterinary products

The Factrel name now belongs to a Zoetis cattle product (50 µg/mL, NADA 139-237). It is approved to treat ovarian follicular cysts in cows and, with dinoprost, to time ovulation for fixed-time artificial insemination (Factrel veterinary label). Other cattle products, such as Cystorelin, carry the warning “Not for use in humans” (Cystorelin label).

Compounding

Because no human gonadorelin product is marketed, human use in the US now relies on compounding. Compounded drugs are not FDA-approved: FDA does not verify their safety, effectiveness or quality before they are marketed (FDA compounding Q&A).

  • 503A pharmacies. FDA says these pharmacies may compound from a bulk substance that has a USP monograph, or that is a component of an FDA-approved drug, or that is on the 503A bulks list (FDA 503A bulk substances). Gonadorelin hydrochloride and acetate were components of the approved Factrel and Lutrepulse.
  • 503B outsourcing facilities. Gonadorelin acetate is in category 1 (“under evaluation”) of FDA’s 503B nominations list, flagged as a component of an FDA-approved drug (FDA 503B categories, March 2025).
  • Not on the safety-risk list. Gonadorelin is not among the substances FDA lists as raising significant safety risks in compounding. Kisspeptin-10, by contrast, was placed on that list in 2023 (FDA category 2 list).

Gonadorelin is not a controlled substance; it is not named in the DEA’s Schedule III list of anabolic steroids (21 CFR 1308.13).

What the research shows

Hypothalamic amenorrhea in women

This was Lutrepulse’s purpose and is the best-studied use.

Study Design and n Dose Results
Santoro, AJOG 1990 Multicenter trial, 109 women Pulsatile IV Lutrepulse Ovulation in 91% (primary) and 96% (secondary amenorrhea); IV-line complications 0–11% (mean 7%); multiple pregnancy 12%
Filicori et al., JCEM 1991 114 women, 187 cycles 2.5–5 µg IV every 60 min Ovulation 93% and conception 23% in primary hypogonadotropic amenorrhea; 91% and 31% in other hypogonadotropic women
Tranoulis et al., Fertil Steril 2018 Meta-analysis, 35 studies (3 randomized), 1,002 women IV or subcutaneous pulses High ovulation rates; subcutaneous similar to IV; OHSS rare and mild; multiple pregnancy slightly above the general population

In the Filicori study, most multiple pregnancies (3 of 4) occurred in women with residual hypothalamic activity given the higher 5 µg dose. For women with polycystic ovary syndrome, a Cochrane review found only 4 small randomized trials (57 women) and could not show benefit or harm (Bayram et al., Cochrane 2004).

Hypogonadotropic hypogonadism in men

In men who cannot make GnRH, pulsatile gonadorelin can restart the whole axis, including sperm production.

Study Design and n Dose Results
Hoffman & Crowley, NEJM 1982 Case series, 6 men Low-dose subcutaneous pulses by pump Testosterone 77 → 520 ng/dL after 1 month; sperm in 3 men by 43 weeks
Zhang et al., Am J Mens Health 2019 Nonrandomized, 28 azoospermic men (10 pump, 18 hCG/hMG) 10 µg subcutaneous every 90 min Sperm in 90% vs 83.3%; median time 6 vs 14 months (p = 0.01)
Wei et al., World J Mens Health 2021 Meta-analysis, 7 studies, 420 men Pulsatile GnRH vs hCG/hMG Sperm appeared about 5.3 months earlier with GnRH; larger testes; no significant difference in sperm detection rate, sperm count or pregnancy rate

The meta-analysis authors noted that no high-quality randomized trials exist. Pump therapy is also more demanding: the Zhang participants changed the needle, reservoir and tubing every 3 days. For comparison with gonadotropin therapy, see the hCG and hMG pages.

Diagnostic stimulation test

A single 100 µg IV bolus of GnRH has been used to test how well the pituitary releases LH, for example in studies of testosterone feedback in men (Finkelstein et al., JCEM 1991). A single bolus measures pituitary reserve; it does not treat anything.

Men on testosterone therapy

Gonadorelin is sometimes discussed as a substitute for hCG to keep the testes active during testosterone therapy. We found no published controlled trial testing this. The available physiology gives reasons for caution:

  • Pulses matter. The human data above show that the pituitary needs repeated pulses about every 1.5–2 hours. After a subcutaneous dose, gonadorelin falls under 10% of its peak within 90 minutes (Hurley et al., JCEM 1987). Studies that restored testicular function used pumps, not once- or twice-daily injections.
  • Testosterone blunts the pituitary directly. In 6 GnRH-deficient men kept on pulsatile GnRH, a 4-day testosterone infusion lowered LH and FSH, showing that testosterone suppresses the pituitary’s response to GnRH, not just the hypothalamus. An aromatase inhibitor blocked this effect, pointing to conversion of testosterone to estradiol (Finkelstein et al., JCEM 1991).

hCG avoids both problems because it acts directly on the testes. Whether intermittent gonadorelin injections preserve testicular size, testosterone production or fertility in men on testosterone has not been studied.

Side effects and risks

Allergic and injection-site reactions

  • Local reactions. Skin allergic reactions were a common side effect with the gonadorelin pump in the Zhang study, and the Wei meta-analysis found that allergic reactions occurred mostly with GnRH therapy.
  • Antibody-mediated reactions. A woman using a Factrel pump developed wheal-and-flare reactions at injection sites; testing showed an immunoglobulin-mediated allergy to the hormone itself (Foster et al., AJOG 1989).
  • Anaphylaxis. An 8-year-old girl lost consciousness within 3 minutes of an IV gonadorelin acetate stimulation test and needed epinephrine. The authors described such reactions as extremely rare and advised testing in settings equipped to treat them (Akın et al., JPEM 2015).

Pump and IV-line problems

IV pumps require an indwelling catheter. In the Lutrepulse trial, IV-line complications occurred in a mean of 7% of patients, and superficial thrombophlebitis (vein inflammation) is a recognized but uncommon problem with IV pulsatile therapy (Santoro, AJOG 1990; Tranoulis et al., Fertil Steril 2018).

Multiple pregnancy and ovarian stimulation

Multiple pregnancy occurred in 12% of women in the Lutrepulse trial. Ovarian hyperstimulation syndrome (OHSS) was rare: one case, in a woman also taking clomiphene. The trial report judged pulsatile GnRH at least as effective as hMG injections, with lower overall risk for women with hypothalamic amenorrhea (Santoro, AJOG 1990).

In the male meta-analysis, gonadotropin therapy (hCG/hMG) was linked to more gynecomastia and acne than pulsatile GnRH (Wei et al., World J Mens Health 2021).

Suppression with continuous exposure

Continuous gonadorelin does not work as a stimulant and, if sustained, can turn the axis off, as described above. This is the mechanism by which GnRH agonists lower testosterone to castrate levels.

Product quality

Compounded and “research” gonadorelin are not FDA-approved products, so their identity, purity and sterility have not been verified by FDA. When Lutrepulse was introduced, its developers noted that impurities and breakdown products might contribute to reactions reported with earlier GnRH products (Wong et al., Int J Fertil 1990).

Use in sport

WADA lists “gonadotrophin-releasing hormone (GnRH, gonadorelin) and its agonist analogues” among testosterone-stimulating peptides banned in males, prohibited at all times, in and out of competition (WADA 2026 Prohibited List). hCG, LH and kisspeptin appear in the same section.

Key takeaways

  • Synthetic natural GnRH. Gonadorelin is identical to the hypothalamic hormone that drives LH and FSH release.
  • Timing is everything. Pulses every 1–2 hours stimulate the pituitary; continuous exposure fails to, and long-acting agonists use that effect to suppress testosterone.
  • Very short-acting. Its IV half-life is about 2–3 minutes, and subcutaneous doses are mostly gone within 90 minutes.
  • Works by pump, in specific patients. In mostly small or nonrandomized studies, pulsatile pump therapy restored ovulation in hypothalamic amenorrhea and sperm production in GnRH-deficient men. It is untested as an hCG substitute during testosterone therapy.
  • No marketed human product. Factrel (1982) and Lutrepulse (1989) are discontinued; US human use is via compounding, where gonadorelin acetate is under FDA evaluation for 503B facilities.
  • Banned in male athletes. WADA prohibits it at all times under S2.2.1.

Sources

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  3. Food and Drug Administration. Drugs@FDA: Factrel (gonadorelin hydrochloride), NDA 018123. FDA.
  4. Food and Drug Administration. Drugs@FDA: Lutrepulse Kit (gonadorelin acetate), NDA 019687. FDA.
  5. Zoetis Inc. Factrel (gonadorelin injection) for cattle, NADA 139-237, label. DailyMed.
  6. Boehringer Ingelheim Animal Health USA Inc. Cystorelin (gonadorelin diacetate tetrahydrate) injectable solution label. DailyMed.
  7. AbbVie Inc. Lupron Depot (leuprolide acetate for depot suspension) prescribing information. DailyMed.
  8. Food and Drug Administration. Bulk drug substances used in compounding under section 503A of the FD&C Act. Content current as of May 14, 2026. FDA.
  9. Food and Drug Administration. Bulk drug substances nominated for use in compounding under section 503B of the Federal Food, Drug, and Cosmetic Act. Updated March 21, 2025. FDA.
  10. Food and Drug Administration. Compounding and the FDA: questions and answers. Content current as of September 16, 2025. FDA.
  11. Food and Drug Administration. Certain bulk drug substances for use in compounding that may present significant safety risks. Content current as of April 22, 2026. FDA.
  12. Drug Enforcement Administration. Schedule III. 21 CFR 1308.13. eCFR.
  13. World Anti-Doping Agency. World Anti-Doping Code International Standard: Prohibited List 2026. WADA 2026 Prohibited List.
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