Gonadorelin: what the studies show, status and safety

Summary

Gonadorelin is a copy of the hormone the brain uses to switch on the sex glands. It is prescription-only, still approved in Britain and Switzerland but discontinued in North America. Given as pulses from a pump, it restored ovulation in nearly every treated cycle in hypothalamic amenorrhoea. The popular claim that it replaces hCG during testosterone therapy has never been studied.

Key findings at a glance

• Approved for people in only two of the seven markets on this page. The United Kingdom licenses it as a diagnostic injection, Switzerland for pump therapy ^[1], ^[2].
• Both American human licences are dead. The diagnostic injection was approved on 30 September 1982 under application NDA 018123, the pump kit on 10 October 1989 under NDA 019687. Every strength of both is now listed as discontinued ^[3], ^[4]. All seven Canadian human registrations are cancelled or dormant ^[5].
• 96 percent of cycles ended in ovulation in 66 women with functional hypothalamic amenorrhoea, across 82 treatments and 212 cycles. Live births followed 65.9 percent of treatments ^[6].
• In men the picture is mixed. Pooling 420 men, sperm appeared 5.30 months earlier than under gonadotropin injections. Sperm concentration (p = 0.37) and pregnancy rate (p = 0.11) did not differ ^[7].
• Nothing is proven in polycystic ovary syndrome. Four randomised trials with 57 women together were too small to show or rule out a benefit ^[8].
• Not one study exists on the use people talk about most. A structured literature search found no clinical trial of gonadorelin alongside testosterone replacement ^[9].
• Banned in sport at all times, but only in men. The 2026 prohibited list names it in section S2.2.1 ^[10].
• Prescription-only in Germany whether or not a product is on sale, because German schedule 1 names the substance itself ^[11].

What it is

Gonadorelin is gonadotropin-releasing hormone, the signal the hypothalamus sends to the pituitary gland roughly once an hour. The medicine is the same molecule, made in a factory: a chain of ten building blocks with a closed front end and an amide at the tail ^[12].

That makes it the parent, not a relative. Leuprorelin, triptorelin, buserelin, goserelin, nafarelin, deslorelin and histrelin are all chemically altered descendants of this one decapeptide ^[12], ^[10].

Brand names identify products rather than describe them. In the United Kingdom, HRF from Esteve Pharmaceuticals is licensed as a single injection that tests how well the pituitary can respond ^[1]. In Switzerland, Lutrelef from Ferring is licensed for hypothalamic amenorrhoea and for central hypogonadism in men ^[2].

The American products are history. FACTREL was the diagnostic injection and LUTREPULSE the pump kit; both are discontinued ^[3], ^[4]. A German commercial database still lists an injection, a pump preparation and a nasal spray. No regulator's register was reachable to confirm that any of them is on sale ^[13].

Quick facts

How it works

Gonadorelin works one floor above the sex glands, at the pituitary, and never touches the ovary or the testicle directly.

• At the pituitary, it docks onto the GnRH receptor of the gonadotroph cells. The label puts it plainly: it "stimulates the synthesis of follicle stimulating hormone and luteinising hormone in the anterior lobe of the pituitary as well as their release" ^[1].
• Downstream, those two hormones do the actual work in the ovary and in the testicle, where they drive egg ripening and testosterone production ^[1].
• The rhythm is the mechanism. In a normal menstrual cycle the body releases the hormone in pulses, at intervals of 60 to 120 minutes during the follicular phase, and only that natural pattern keeps the receptor responsive ^[8].
• A steady supply does the opposite. Continuous exposure blunts the receptor and shuts the axis down after a short initial burst ^[16].
• The molecule disappears in minutes, which is why a single injection can only ever be a short test, and why long-term treatment needs a portable pump ^[1], ^[15].

This is the dividing line to the depot agonists. Leuprorelin and its relatives are given as long-acting formulations precisely so that they suppress the axis. That suppression is what makes them useful in prostate cancer, endometriosis and early puberty ^[1], ^[16].

What the studies found

Ovulation in women whose periods have stopped

Observational cohort The strongest single dataset comes from a Swiss university hospital, which followed every woman treated with a GnRH pump between 1996 and 2020.

Sixty-six women with functional hypothalamic amenorrhoea received 82 treatments over 212 cycles. Ovulation occurred in 96 percent of cycles, and in 75 percent of them only one follicle matured, which is what keeps twin pregnancies rare ^[6].

Live births followed 65.9 percent of treatments. Biochemical pregnancies followed 80.5 percent, and the cumulative clinical pregnancy rate reached 74.4 percent. Miscarriages occurred in 11.5 percent, and one twin pregnancy arose, or 1.6 percent ^[6].

Birth weights matched those of a comparison group. Two of the authors declared that they advise or lecture for the company that sells the preparation ^[6].

Meta-analysis The largest evidence synthesis pooled 1,002 women from 35 studies, of which only three were randomised and 32 were observational ^[17].

Its authors report high ovulation rates, a tendency towards high pregnancy and live birth rates per ovulatory cycle, and comparable results whether the pump fed a vein or the skin. Ovarian hyperstimulation was rare and mild, multiple births were slightly above the general population, and superficial vein inflammation appeared only with the intravenous route ^[17].

One limitation matters for anyone quoting this paper. The abstract attaches no percentage and no confidence interval to any of those endpoints, so the often-repeated figure of 80 to 90 percent cannot be traced to it ^[17].

Small open series An early dose-comparison series treated ten patients over 26 cycles in three groups. Ovulation followed in 80 percent of ten cycles, 92.3 percent of thirteen and 100 percent of three; pregnancies followed 25 and 41.6 percent in the first two groups ^[18].

Oestradiol curves and mean luteal progesterone were the same in all three groups. The authors concluded that every amount tested worked, while the lowest might sit at a threshold below which the ovary responds too weakly ^[18].

A later series treated twelve women over 33 cycles. All of them ovulated, on average after 17 days on the pump, and 30 of the 33 cycles produced a single egg. Ten pregnancies arose in seven patients ^[19].

Sperm production in men

Meta-analysis Seven comparative studies covering 420 men set the pump against injected gonadotropins in congenital hypogonadotropic hypogonadism ^[7].

The pump was linked to larger testicles (standardised mean difference -1.43; p = 0.01) and to sperm appearing 5.30 months earlier (weighted mean difference; p = 0.004). Three endpoints showed no difference at all: whether sperm were found (p = 0.08), how concentrated they were (p = 0.37) and whether a pregnancy followed (p = 0.11) ^[7].

Side effects sorted themselves by treatment. Allergic reactions occurred mostly on the pump, while breast tissue growth and acne were more common under gonadotropins. The authors asked for proper randomised trials, which still do not exist ^[7].

Observational A Chinese hospital compared 40 men on the pump with 52 on hCG plus hMG, with patients choosing their own treatment. Sperm appeared in 50.0 percent on the pump against 28.8 percent on injections (p = 0.038), after 6.5 ± 3.1 against 10.8 ± 3.7 months (p = 0.001) ^[20].

Testosterone tells the opposite story. On the pump it rose from 1.0 ± 1.0 to 7.4 ± 5.2 nmol/l. On injections it rose from 0.8 ± 0.6 to 14.4 ± 8.0 nmol/l, both p < 0.01.

Testicular volume grew similarly in both groups, from 2.3 ± 1.5 to 8.1 ± 4.0 ml and from 2.3 ± 2.1 to 7.6 ± 4.2 ml ^[20].

Observational A switching series took 28 men who had responded poorly to at least six months of gonadotropins, a median of 12.5 months. Sperm appeared in 17 of them, or 60.7 percent, after a median of 12.0 months on the pump ^[21].

The men who succeeded had reacted more strongly to a stimulation test beforehand. Luteinising hormone reached 4.32 against 1.10 IU/l after 60 minutes (p = 0.043), follicle-stimulating hormone 4.28 against 1.90 IU/l (p = 0.021) ^[21].

As a diagnostic test

Observational A single centre reviewed 584 stimulation tests in children, 314 to diagnose early puberty and 270 to check whether treatment was holding puberty back ^[22].

The test itself is a hospital procedure. Staff give the injection into a vein and draw blood several times over the following hour, and the study asked how many of those samples a laboratory really needs.

In that dataset the sample drawn 40 minutes after the injection held the peak luteinising hormone value most often (p < 0.001). Measured against a threshold of 5 IU/l, that single sample matched the full test in identifying early puberty, with a sensitivity of 98 percent and a specificity of 100 percent. For checking suppression, the 20-minute sample reached 100 percent on both counts ^[22].

The test has real limits. It performs poorly at the very start of puberty, in girls whose results overlap with normal ones, and in children with obesity, because surplus oestrogen pushes luteinising hormone down. There is also no agreed threshold, so different centres use different numbers ^[23].

The label is blunter still: "The single injection test does not determine the patho-physiological cause for the subnormal response and does not measure pituitary gonadotropic reserve." A normal result shows only that working gonadotroph cells are present ^[1].

Where the evidence is negative or missing

Cochrane review In polycystic ovary syndrome the pump has never been shown to help. Four randomised trials covering 57 women made four different comparisons, each followed for one to three cycles ^[8].

The single comparison that reported ongoing pregnancy gave an odds ratio of 7.5, with a range from 0.44 to 127. That range includes 1, so the result shows nothing. No multiple pregnancies occurred, and ovarian hyperstimulation appeared only in the hMG group ^[8].

The reviewers' own conclusion is worth quoting: the four trials "were too small to either prove or discard the value of pulsatile GnRH treatment in patients with polycystic ovary syndrome" ^[8]. In a separate series, the one treated patient with the syndrome had an early hormone surge and no ovulation ^[19].

No studies The use discussed most often online has never been examined. A structured search on 10 September 2026 for gonadorelin alongside testosterone replacement returned 376 records, none of them on the question. A search for compounded gonadorelin returned a single paper about lipid nanoparticles ^[9].

A 2026 review of peptides sold as performance enhancers does not list gonadorelin either. It covers the growth hormone axis and stops there ^[24].

What is still unknown

• No randomised comparison exists against gonadotropin injections for long-term therapy. Every meta-analysis rests on observational data ^[7], ^[17].
• The registers hold almost nothing. Of the first 100 trial records returned for gonadorelin, exactly one names the substance itself as the intervention, a study in 46 girls ^[25].
• Antibody formation is listed but not quantified. The label records a rare positive antibody test and no more ^[1].
• Kidney and liver impairment are covered by one sentence in a commercial database, not by a study ^[13].
• Recovery happens on its own in some men. Around 10 percent of men with congenital hypogonadotropic hypogonadism regain their own hormone axis. That complicates the reading of every uncontrolled series ^[26].
• Material from the grey market is unstudied. No purity, sterility or content data exist for it.

Side effects and safety

Most reported reactions are mild and local, but the serious ones arrive fast. The frequency labels below follow the standard convention: uncommon means between 1 in 1,000 and 1 in 100, rare means between 1 in 10,000 and 1 in 1,000 ^[1].

• Uncommon: pain; swelling and itching at the injection site ^[1].
• Rare: headache, dizziness, nausea, abdominal discomfort, hardening of the skin where the injection went in. Also a fast heartbeat, flushing, hives, redness of the skin and eyelids, hypersensitivity reactions, bronchospasm and a positive antibody test ^[1].
• Frequency not known: sepsis, heavy menstrual bleeding, vein inflammation with clotting, rash ^[1].

Anaphylaxis is the reaction that decides where this substance may be given. A published case describes an eight-year-old girl with central precocious puberty. She lost consciousness within three minutes of an injection into a vein and developed cramps in her hands and feet ^[27].

Her vital signs recovered within 30 minutes after adrenaline, an antihistamine and fluids. A second such reaction was reported in 1993. The authors conclude that the injection belongs in a setting equipped for systemic reactions ^[27], ^[28].

The label carries three further warnings, all quoted here in its own words ^[1]:

• On repeat use: the label first records that no allergic or hypersensitivity reaction had been seen after a single diagnostic injection at the time of writing, and then adds that "patients in whom re-administration is considered, particularly by the intravenous route, should be carefully observed".
• On pituitary tumours: the label advises against use in anyone with a pituitary adenoma, because bleeding into the gland, known as pituitary apoplexy, may follow.
• On timing within the cycle: "Administration during the follicular phase of a normal cycle may result in premature ovulation and appropriate measures are advised to prevent an unwanted pregnancy in these circumstances."

Overstimulation of the ovaries is a known risk of any ovulation treatment. Under pulsatile therapy the large meta-analysis found it rare and mild, and in the Cochrane review it appeared only in the comparison group ^[17], ^[8].

The substance must not be used in anyone hypersensitive to it, or in known or suspected pregnancy, and not during breastfeeding. A German database adds hormone-dependent tumours, ovarian cysts, a pituitary prolactinoma and absent ovulation that is not hypothalamic in origin ^[1], ^[13].

Several medicines disturb the test. Androgens, oestrogens, progestogens and glucocorticoids act on pituitary gonadotropin release directly. Spironolactone raises gonadotropin levels temporarily, methyldopa slightly, while oral contraceptives and digoxin suppress them. Phenothiazines and dopamine blockers can blunt the response by raising prolactin ^[1].

Larger amounts, given twice daily for 28 days, produced no signs of overdose in the label's account, which advises symptomatic treatment if one occurs. Animal studies of safety, repeat dosing, genetic damage, cancer risk and reproduction revealed "no special hazard for humans" ^[1].

Safety and effectiveness in children under one year of age have not been established, and no data exist ^[1].

Why this page lists no doses

Gonadorelin is a prescription medicine wherever it is sold, named in German schedule 1 and in Australian schedule 4 regardless of what is on the market ^[11], ^[29]. Amounts, pulse intervals and test procedures belong in a prescription and in the approved product information, so this page reports what studies measured without repeating what they gave.

Development and approval status

• 1982 — the first American licence is granted on 30 September, as a new molecular entity with priority review ^[3].
• 1989 — a second American licence follows on 10 October, for the pump kit ^[4].
• 1996 to 2019 — the Canadian diagnostic registrations are cancelled, on 10 September 1996, on 26 October 1999 and on 4 July 2019 ^[5].
• 2001 — the British authorisation is granted on 25 May and renewed on 25 June 2004 ^[1].
• 2017 to 2024 — the Canadian pump product goes dormant, and the last human registration there is cancelled on 24 December 2024 ^[5].
• 2026 — an expert paper advises how to treat infertility "until pulsatile GnRH therapy becomes available again", without naming a reason for the shortage ^[16].

No date could be found for the American discontinuation. The register records the status without one, and four targeted searches of the federal gazette returned nothing, because its full-text index does not reach back far enough ^[3], ^[4].

The empty rows were each checked against a control term that did return results. The European export holds nothing for gonadorelin while returning leuprorelin, triptorelin and choriogonadotropin ^[32]. The Spanish register holds nothing against 13 entries for leuprorelina ^[33]. The Russian query failed outright, since even the control term returned no rows, and it therefore proves nothing ^[34].

What remains widely available is the veterinary version. American labels for cattle exist under NADA 139-237, NADA 098-379 and ANADA 200-134, and six Canadian veterinary registrations are still marketed ^[35], ^[5]. All of them are restricted to use by a vet, and none says anything about people ^[36].

The raw substance is a separate story. On 10 September 2026 the American drug code directory held 13 registrations of gonadorelin as an unfinished ingredient, from eight filers in Europe, the United States, China and India. Twelve are declared as bulk ingredient, one as bulk ingredient for human prescription compounding ^[37].

Its absence from the compounding lists is easy to misread. Gonadorelin appears neither in the six-substance list of section 216.23 nor in section 216.24 ^[38]. It is also absent from the American list of ingredients judged to carry significant safety risks, which does name GHRP-2, GHRP-6, ipamorelin and kisspeptin-10 ^[39].

Absence there means the regulator has not assessed it, not that compounding is cleared. No warning letter names the substance either, in a table of 2,658 records ^[40]. The wider framework is set out under are peptides legal.

Every entry reflects the position on 10 September 2026.

Anti-doping

Gonadorelin is banned in male athletes at all times, in and out of competition, and everything in its class counts as a non-specified substance ^[10].

The 2026 prohibited list names it directly in section S2.2.1, headed "Testosterone-stimulating peptides in males": "gonadotrophin-releasing hormone (GnRH, gonadorelin) and its agonist analogues (e.g. buserelin, deslorelin, goserelin, histrelin, leuprorelin, nafarelin and triptorelin)" ^[10].

The words "in males" sit in the heading and cover every substance listed under it. This is one of the few sex-specific rules on the whole list ^[10]. German anti-doping law repeats no such limit and names gonadorelin in section II number 2.1 without qualification ^[41].

An American voluntary testing programme uses nearly identical wording, and the racing authority has written gonadorelin into its medication rule for horses ^[42], ^[43]. A German drug database warns prescribers directly that the substance can produce a positive doping test ^[13]. More on this class at peptides banned in sport.

Compared with related peptides

The first four sit on one axis and behave very differently on it. Gonadorelin and kisspeptin push the axis upwards, hCG bypasses it and works on the gland itself, and leuprorelin shuts the axis down by never letting the receptor rest ^[1], ^[16].

That difference in direction has a clinical consequence. If the pituitary itself has failed, gonadorelin does nothing at all, while hCG still works, because it reaches the testicle without passing through the pituitary ^[1].

Oxytocin is here as a contrast rather than a relative. It comes from the back lobe of the same gland and acts on the womb and the breast, so it shares an address and nothing else ^[44].

Doping rules follow the biology. Everything that raises a man's own testosterone sits in one entry, whichever end of the axis it grips, while oxytocin appears nowhere on the list ^[10].

Common misconceptions

• "Gonadorelin is a GnRH analogue like leuprorelin." It is the other way round. Gonadorelin is the hormone; the analogues are its altered descendants. Pulses of gonadorelin switch the axis on, while depot agonists switch it off after a brief initial surge ^[1], ^[16].
• "Pulsed or in one shot, it is the same substance." The timing is the mechanism. In a normal cycle the body's own hormone arrives at intervals of 60 to 120 minutes during the follicular phase, and only that rhythm keeps the receptor working; a steady supply blunts it. That is why the licensed single injection can only ever be a short test ^[8], ^[1].
• "Gonadorelin works like hCG." Both raise testosterone, but at different places. hCG acts on the testicle directly, gonadorelin on the pituitary above it, and it needs a working pituitary to do anything. In the one head-to-head cohort, testosterone rose to 14.4 ± 8.0 nmol/l on hCG against 7.4 ± 5.2 on the pump ^[1], ^[20].
• "It replaces hCG during testosterone therapy." No clinical study has tested that. Every solid finding in men comes from pump therapy in patients who are not taking testosterone. Injected testosterone suppresses the pituitary, which is exactly the level gonadorelin depends on ^[9].
• "It is FDA-approved." Not for people, not any more. Both American human licences are discontinued and no human product remains in the American label archive, only five veterinary ones ^[3], ^[4], ^[36].
• "It is licensed for animals, so it must be harmless." Cattle labels cover heat and ovulation control and are tied to a vet's order. They say nothing about people. Gonadorelin is not even the strongest option in that field: in twelve Holstein cows its peak hormone response was 2.5 times lower than that of lecirelin or buserelin ^[45], ^[35].
• "Ovulation rates near 90 percent apply to any cycle problem." They apply to hypothalamic amenorrhoea, where the defect sits exactly where the medicine acts. In polycystic ovary syndrome the benefit is unproven, and where the pituitary itself has failed the substance does nothing ^[6], ^[8], ^[1].

Frequently asked questions

Is gonadorelin approved by the FDA?

Not for human use any more. Two American licences existed, one for a diagnostic injection from 30 September 1982 and one for a pump kit from 10 October 1989, and every strength of both is now listed as discontinued. No discontinuation date is recorded. Five gonadorelin products remain in the American label archive, and all five are veterinary.

Where is gonadorelin still an approved medicine?

In the United Kingdom and in Switzerland. The British authorisation PL 17509/0005 covers a single injection used to test how the pituitary responds. The Swiss authorisation 31628 covers a preparation for pump therapy in hypothalamic amenorrhoea and in central hypogonadism in men. Canada has cancelled or suspended all seven of its human registrations.

What does gonadorelin actually do in the body?

It docks onto a receptor in the pituitary gland and makes it release luteinising hormone and follicle-stimulating hormone. Those two then act on the ovary or the testicle. Gonadorelin never reaches the sex glands itself, which is why it does nothing when the pituitary has failed.

Why does gonadorelin only work in a pulsed rhythm?

Because the rhythm, not the substance, carries the effect. In the body the hormone arrives at intervals of 60 to 120 minutes during the follicular phase, and only that pattern keeps the receptor responsive. A steady supply blunts it and shuts the axis down. The molecule also disappears from the blood within minutes.

Does gonadorelin help women who are not ovulating?

In one specific group, yes. In 66 women with functional hypothalamic amenorrhoea, 96 percent of cycles ended in ovulation and 65.9 percent of treatments in a live birth. In polycystic ovary syndrome the picture is different: four randomised trials with 57 women were too small to prove or rule out any benefit.

Does gonadorelin work better than hCG injections for male fertility?

Partly, and not on the endpoints that matter most. Pooling 420 men, sperm appeared 5.30 months earlier on the pump, but sperm concentration and pregnancy rates did not differ. In a 92-man cohort more men on the pump produced sperm, while testosterone rose roughly twice as high on hCG plus hMG.

Is gonadorelin a safe replacement for hCG during testosterone therapy?

There is no evidence either way, which is itself the answer. A structured literature search in September 2026 found no clinical study of gonadorelin alongside testosterone replacement. Every reliable finding in men comes from pump therapy in patients not taking testosterone, and injected testosterone suppresses the very gland gonadorelin acts on.

What are the side effects of gonadorelin?

Mostly mild and local: pain, swelling and itching are uncommon, while headache, dizziness, nausea, flushing, a fast heartbeat and hives are rare. The reaction that shapes practice is anaphylaxis. One published case involved a child who lost consciousness three minutes after an injection into a vein and recovered within half an hour.

Is gonadorelin banned in sport?

For male athletes, at all times. The 2026 prohibited list names it in section S2.2.1, headed testosterone-stimulating peptides in males, and everything in that class is a non-specified substance. The restriction to men is unusual and easy to miss. German anti-doping law names gonadorelin with no such limit.

Is gonadorelin legal to buy without a prescription?

No. German schedule 1 names the substance itself, so the prescription requirement holds whether or not a product is on sale, and German anti-doping law names it separately. Australia lists it in schedule 4. It is a prescription medicine in every market covered on this page.

Cite this page

The facts on this page were checked on 10 September 2026, and every register behind the status table was queried on that same day. Legal schedules and doping lists change from year to year, so the version and the date matter as much as the text.

myPeptides Research & Editing. (2026). Gonadorelin: what the studies show, status and safety. Version 1.0, 10 September 2026. myPeptides Peptide Register. Retrieved from https://mypep.app/peptides/gonadorelin

How pages in this register are compiled and graded is described under methodology; the full register is at peptides.

Last verified: 10 September 2026. Next review: on any change to the anti-doping list, to the British or Swiss authorisations, or on any new human study.