Triptorelin: The GnRH Agonist That Switches the Axis Off, the Approved Uses, and the Single-Dose Myth

Triptorelin: The GnRH Agonist That Switches the Axis Off, the Approved Uses, and the Single-Dose Myth

Triptorelin is what happens when you take the native GnRH decapeptide, swap one amino acid, and remove the gap between pulses. Gonadorelin lasts minutes and stimulates; triptorelin lasts hours, is packaged in depots that last months, and suppresses. The same receptor, the opposite outcome, and both outcomes are used in medicine: triptorelin has held testosterone at castrate levels in men with prostate cancer since the 1980s, paused puberty in children who started it too early, and given IVF clinics a way to trigger egg maturation without the ovarian hyperstimulation that hCG can cause. It is also, in the research-compound market, the subject of a persistent belief that one small injection restarts a steroid-suppressed axis. That belief rests on a single published patient, and the pharmacology explains both why it looked true once and why repeating it is a different experiment. This reference sets out the molecule, the approved evidence, and the myth.

Michael Phelps

Founder & Peptide Research Specialist, PrymaLab

Research reference · Last updated September 23, 2026 · ~25 min read

What triptorelin is: GnRH with one D-amino acid

Gonadotropin-releasing hormone is ten amino acids long, and in the hormone the sixth is a glycine. Triptorelin keeps nine of the ten and replaces that glycine with D-tryptophan, the mirror image of the natural amino acid: pGlu-His-Trp-Ser-Tyr-D-Trp-Leu-Arg-Pro-Gly-NH₂, molecular formula C₆₄H₈₂N₁₈O₁₃, molecular weight 1,311.47 g/mol, CAS 57773-63-4.^[1] Position 6 is where the native peptide bends and where serum proteases cut it, so a D-amino acid there does two things at once: it stabilises the bioactive shape and it blocks the cut. The result binds the pituitary GnRH receptor more tightly and survives in blood far longer than the hormone it copies.

It came out of Andrew Schally's laboratory at Tulane, the same group that had characterised GnRH itself; it was patented in 1975, licensed to Debiopharm in 1982 and approved for medical use in 1986.^[1] Two salts are used. The acetate is the soluble form, given as a daily or single injection and the form a research vial contains. The pamoate is a poorly soluble salt formulated into microparticle depots that release the peptide over months, and it is what the prostate-cancer and puberty products are made of. Brand names track the market: Trelstar and Triptodur in the United States, Decapeptyl from Ipsen and Diphereline and Gonapeptyl from Ferring in Europe, Salvacyl in the UK and Germany, Variopeptyl in Iran.^[1] The World Health Organization lists it as a therapeutic alternative on its List of Essential Medicines.^[1]

By the definition in the what counts as a peptide reference it is a peptide without qualification, and the gonadorelin reference covers the unmodified hormone it descends from. The two articles are two halves of one story, and the hinge is the rule that article establishes: pulsed GnRH stimulates, continuous GnRH suppresses. Triptorelin is that rule turned into a drug.

The flare, the shutdown, and why the depot matters more than the peptide

The Trelstar prescribing information states the mechanism in two sentences. Triptorelin initially causes a transient surge in LH, FSH and testosterone. After 2 to 4 weeks of continuous therapy a sustained decrease in these hormones occurs, achieving 'reduction of serum testosterone concentration to a level typically seen in surgically castrated men'.^[2] That is the whole pharmacology, and both halves matter.

The surge is the agonist doing what an agonist does: it binds the receptor and the pituitary releases what it has. In a man with prostate cancer that surge can briefly feed the tumour, which is why the label warns of a 'transient increase in serum testosterone levels' in the first weeks and clinicians cover the flare with an anti-androgen.^[2] The shutdown is the receptor's response to being occupied without a break: it downregulates and stops signalling, LH release falls, and the gonad, no longer instructed, stops making sex steroid. This is the 1978 monkey experiment described in the gonadorelin reference, run in reverse and on purpose.

The peptide itself does not last long. After a subcutaneous dose, serum levels peak within 1 to 3 hours and the half-life in healthy volunteers is about 2.8 hours, rising to 6.6 to 7.7 hours with liver or kidney impairment; 41.7% is excreted unchanged by the kidney, and metabolism 'is unlikely to involve hepatic microsomal enzymes'.^[2] What produces months of suppression is the depot: the pamoate microparticles release 38.3% of the dose in the first 13 days, about 2.9% a day, and then about 0.92% of the dose per day thereafter.^[1] A 2.8-hour peptide becomes a six-month drug through formulation. A research vial of the acetate has none of that; it delivers the surge and clears.

The approved uses and what the trials showed

Triptorelin's evidence base is unusual for a compound in this library: it is a licensed drug with prescribing information written by regulators, and the numbers below are label facts about approved products given under medical supervision.

Advanced prostate cancer. Trelstar, first approved in the United States in 2000, is indicated for the palliative treatment of advanced prostate cancer as an intramuscular depot of 3.75 mg every 4 weeks, 11.25 mg every 12 weeks or 22.5 mg every 24 weeks. In the registration studies, testosterone reached castrate levels by day 29 in 91.2%, 97.7% and 97.5% of men respectively, and stayed there through day 253 in 96.2% and 94.4% for the first two strengths and through day 337 in 93.3% for the six-month depot.^[2]

Central precocious puberty. Triptodur, a 22.5 mg depot given once every 24 weeks, is indicated for children aged 2 years and older with central precocious puberty, the condition in which the hypothalamic-pituitary axis switches on years too early. In its trial, 44 children aged 2 to 9 (39 girls, 5 boys) were treated; 93% had LH suppressed to prepubertal levels of 5 IU/L or below at month 6 and 98% at month 12.^[3] The FDA approved it in 2017.^[4] The label carries the same flare warning in paediatric form, 'a transient increase in clinical signs and symptoms of puberty, including vaginal bleeding', in the first weeks, and warnings for psychiatric events, convulsions and pseudotumor cerebri that apply to the GnRH-agonist class.^[3]

Endometriosis, fibroids and the rest. European labels add endometriosis, reduction of uterine fibroids before surgery, and, for Salvacyl, hypersexuality with severe sexual deviation.^[1] Triptorelin is also used off-label to suppress puberty or sex-hormone production in transgender care; that use sits outside this reference, which reports the licensed indications and their trial numbers.

The IVF uses: suppression, and the agonist trigger

Two very different things are done with triptorelin in fertility medicine, and they illustrate the two-phase pharmacology better than anything else.

The first is suppression. In a long IVF protocol the agonist is given daily to shut the pituitary down so that a stimulated cycle cannot be spoiled by a premature LH surge. The minimal daily dose of triptorelin acetate needed for that has been determined as 15 micrograms, and 50 micrograms performs the same as 100 in IVF outcomes.^[1] That is the downregulation phase, used deliberately.

The second is the opposite phase, used just as deliberately. In an antagonist cycle the pituitary has been kept responsive, and a single dose of agonist at the end of stimulation produces exactly the surge the label warns about: an endogenous LH peak that matures the eggs, in place of the hCG injection that has done that job for decades. Because the agonist-induced surge is short and hCG's is long, the agonist trigger nearly abolishes ovarian hyperstimulation syndrome. The 2014 Cochrane review pooled 17 randomised trials in 1,847 women: in fresh autologous cycles the agonist trigger cut the odds of OHSS to 0.15 (95% CI 0.05 to 0.47; 8 trials, 989 women), but it also lowered the odds of live birth to 0.47 (0.31 to 0.70; 5 trials, 532 women) and of ongoing pregnancy to 0.70 (0.54 to 0.91), because the short surge leaves the corpus luteum under-supported. In donor cycles there was no difference in live birth and far less OHSS. The reviewers' conclusion: the agonist trigger 'could be useful for women who choose to avoid fresh transfers, women who donate oocytes to recipients or women who wish to freeze their eggs'.^[5]

Read the two uses together and you have the compound in miniature. One dose: a surge. Daily doses: a shutdown. Same vial.

The single-dose steroid-recovery idea, and the one patient behind it

Search for triptorelin outside the clinic and most of what comes back is a claim that a single 100 microgram injection 'restarts' the hypothalamic-pituitary-gonadal axis after a course of anabolic steroids. The claim has a source, and the source is worth reading in full, because it is a single case report.

In 2010, physicians at the University of Brescia published in Fertility and Sterility the case of a 34-year-old man who had used anabolic steroids bought on the internet for 13 years, in cycles that included nandrolone, stanozolol, mesterolone, boldenone, clomiphene and hCG, and who presented with hypogonadotropic hypogonadism that had persisted for at least four months after stopping. As part of his work-up he received a single 100 microgram dose of triptorelin, the standard GnRH stimulation test. LH and FSH rose within minutes, his testosterone was 7 ng/mL ten days later, and it remained normal at three weeks.^[6][7]

Three things follow from the pharmacology above. First, a single dose of any GnRH agonist produces the flare, so a rise in LH and testosterone after one injection is the expected response of a working pituitary, not evidence of a lasting reset; the case report's own value was diagnostic. Second, I could not find a controlled study of triptorelin for steroid-induced hypogonadism in the sixteen years since, in any population, so the idea has never moved past n=1. Third, and most important, the same molecule given repeatedly does the opposite of what the protocol intends: continuous agonist exposure downregulates the receptor and suppresses testosterone to castrate levels within 2 to 4 weeks, which is precisely what it is licensed to do.^[2] A protocol that 'repeats the dose to be sure' is a protocol for the second box on the timeline, not the first. The peptides for men overview and the gonadorelin reference cover the axis in more detail; nothing in either supports the myth.

What the labels say about safety

Triptorelin's adverse effects are, for the most part, the intended effect experienced as symptoms: they are what castrate testosterone does to a man or what paused puberty does to a child. On the Trelstar label the most common adverse reactions are hot flushes (58.6% to 73.0% across the three strengths), skeletal pain (12.1% to 13.2%), impotence or erectile dysfunction (7.1% to 10.0%) and, at the six-month strength, testicular atrophy (7.5%).^[2] The warnings are the class warnings for androgen deprivation: the transient testosterone rise in the first weeks and the tumour flare it can cause; QT prolongation; hyperglycaemia and an increased risk of diabetes; and increased cardiovascular risk including myocardial infarction and stroke.^[2]

The paediatric label adds warnings that are specific to suppressing a developing axis: a transient increase in pubertal signs including vaginal bleeding in the first weeks; psychiatric events, with 'symptoms of emotional lability, such as crying, irritability, impatience, anger, and aggression' reported; post-marketing reports of convulsions with GnRH agonists; and pseudotumor cerebri, with instructions to monitor for headache, papilloedema, blurred vision and vision loss. The most common adverse reactions in the Triptodur trial were injection-site reactions, menstrual or vaginal bleeding, hot flush, headache, cough and infections.^[3] The general warning in the Wikipedia summary, which lists anaphylaxis, mood changes, depression, ovarian cysts and changes in blood pressure among reported effects, is consistent with the labels.^[1]

None of this is a safety record for research-grade acetate given as an injection outside a clinic, for which no data exist; it is the record of a prescription depot in patients who needed their axis switched off.

Triptorelin vs the other GnRH analogues, and vs gonadorelin

Every GnRH agonist on the market is native GnRH with a D-amino acid at position 6 and, usually, a change at the C-terminus. Leuprolide has D-leucine at 6 and an ethylamide replacing the terminal glycinamide; goserelin has D-serine(tBu) at 6 and an azaglycine at 10; buserelin, histrelin, nafarelin and deslorelin follow the same pattern with different substitutions. Triptorelin is the one whose only change is the D-tryptophan at 6.^[1] They differ in potency and in the depot technologies built around them, and they share the pharmacology: flare, then suppression, in men and women and children alike. Nafarelin is worth naming because it is the approved nasal GnRH agonist, used to suppress the axis in endometriosis and precocious puberty; no triptorelin nasal product is approved anywhere, and no human pharmacokinetics exist for intranasal triptorelin at research-market strengths.

The GnRH antagonists, ganirelix, cetrorelix, degarelix and the oral elagolix and relugolix, block the receptor outright and suppress without a flare, which is why they have taken over parts of IVF and, in degarelix and relugolix, parts of prostate cancer. Kisspeptin-10 acts one step upstream, on the neurons that release GnRH, and the kisspeptin reference covers it. hCG acts one step downstream, on the gonad, and is what triptorelin's trigger replaces; the hCG guide covers that side.

Where triptorelin stands: an approved drug, a WADA-listed substance, a research compound

Triptorelin is an approved prescription drug in the United States, across Europe and in most of the world, which makes it different from almost every other compound in this library and changes what 'research use' means. An approved product is what a patient receives; research-grade acetate in a vial is the same peptide without the pharmaceutical manufacturing, the depot formulation, the label or the prescriber, and it is legal to sell and hold for laboratory research and not for human use. The legal status guide sets out that framework. Triptorelin is not on FDA's 503A or 503B bulk-substance lists because it does not need to be: approved products exist.

For athletes the position is explicit. The 2026 WADA Prohibited List names it in S2.2.1, testosterone-stimulating peptides in males: 'gonadotrophin-releasing hormone (GnRH, gonadorelin) and its agonist analogues (e.g. buserelin, deslorelin, goserelin, histrelin, leuprorelin, nafarelin and triptorelin)', prohibited at all times.^[8] The listing is written for the flare, since a single dose stimulates testosterone; it applies regardless of which phase a user intends.

Research-grade triptorelin: what to verify

Triptorelin is an easy peptide to verify and a hard one to misread. Identity is by mass spectrometry against the 1,311.5 Da parent; the D-tryptophan does not change the mass, so a chiral method or a certificate stating the D-configuration at position 6 is what distinguishes triptorelin from a mis-synthesised all-L peptide, which would be a weak, short-lived agonist rather than a superagonist. Purity is by HPLC by lot, and net peptide content matters because the acetate counter-ion and water add mass. The purity testing guide covers each of these. PrymaLab's 2 mg vial, autoinjector and nasal spray are documented on that basis; ask the same of any supplier, and ask them which salt they are selling, because a research vial should be the acetate and a listing that describes pamoate depot pharmacology is describing a product it does not contain.

Handling is simpler than for gonadorelin. The D-amino acid gives triptorelin a serum half-life of hours rather than minutes, and the lyophilised acetate keeps for months refrigerated or frozen; reconstituted solution should be refrigerated and used within weeks. The peptide calculator converts a 2 mg vial and its diluent into a concentration for bench work, and the storage guide covers the general practice.

The version of the story the record supports: a one-residue variant of GnRH that binds hard and lasts, engineered into depots that hold the reproductive axis off for months; forty years of licensed use in prostate cancer, precocious puberty, endometriosis and IVF with the numbers to show for it; a receptor whose response depends entirely on whether the signal has gaps; and a research-market belief in a single-dose reset that traces to one patient and contradicts the drug's own label.

What this article does not settle

Single-dose recovery after steroids. One case report, no controlled study, and a pharmacology that predicts the opposite on repeat dosing. The article reports the case; it does not endorse the inference.

Intranasal triptorelin. No approved nasal product and no published human pharmacokinetics; nafarelin is the nasal GnRH agonist with a label.

Recovery time after a depot. The labels describe suppression, not the interval to normal function after the last injection, which varies and is not stated.

Long-term outcomes of puberty suppression outside central precocious puberty. Outside this reference's scope; the labels cover CPP and nothing else.

Live birth after an agonist trigger with modern luteal support. The 2014 Cochrane figures predate some current protocols; the OHSS result has held up, the live-birth penalty may have narrowed.

What is well established: the sequence, mass and salts; the flare-then-suppression mechanism and its 2 to 4 week time course; the depot release kinetics; the Trelstar and Triptodur registration results; the Cochrane trigger figures; the WADA listing; and the size of the evidence behind the single-dose idea.

Triptorelin, D-Trp6-GnRH, Trelstar and Decapeptyl: what the names refer to

Triptorelin is the international non-proprietary name; the 'trip' is for tryptophan and the '-relin' suffix marks a releasing-hormone analogue. D-Trp6-GnRH, D-Trp6-LHRH and [D-Trp6]-GnRH all describe the structure: gonadotropin-releasing hormone with D-tryptophan at position 6; LHRH, luteinising hormone-releasing hormone, is the older name for the same native hormone.^[1] Triptorelin acetate and triptorelin pamoate (or embonate) are the two salts, the first a soluble solution form and the second the poorly soluble salt used in depot suspensions. Trelstar and Triptodur are the United States brands, for prostate cancer and central precocious puberty; Decapeptyl (Ipsen) and Diphereline and Gonapeptyl (Ferring) are the European brands; Salvacyl and Variopeptyl are national brands.^[1] 'Trip' is research-market shorthand. None of the names denotes a different peptide.

Frequently asked questions

References