Triptorelin is a synthetic decapeptide agonist of gonadotropin-releasing hormone (GnRH), the hypothalamic signal that directs the pituitary gland to release luteinizing hormone (LH) and follicle-stimulating hormone (FSH). Marketed in the United States as Trelstar and Triptodur and in Europe and the United Kingdom as Decapeptyl and Gonapeptyl, it suppresses sex hormone production in advanced prostate cancer, central precocious puberty, endometriosis, uterine fibroids, and premenopausal hormone-receptor-positive breast cancer.
Like leuprolide, triptorelin acts in 2 phases depending on exposure duration. A single injection or the first days of a depot shot trigger an acute surge (“flare”) in LH, FSH, and testosterone, which is why single microgram doses have been studied as diagnostic pituitary stimulation tests in men and boys. Under continuous exposure from a sustained-release depot, pituitary GnRH receptors downregulate and serum testosterone drops into the castrate range (50 ng/dL or less) within 2 to 4 weeks.
This page summarizes what regulatory labels, clinical trials, and endocrine studies report as of November 2026. It is for education only and is not medical advice.
| Property | Detail |
|---|---|
| Drug class | GnRH agonist (synthetic decapeptide analog of native GnRH, D-Trp⁶-GnRH) |
| Formula / weight | Free base: C₆₄H₈₂N₁₈O₁₃, 1311.4 g/mol; pamoate salt: C₈₇H₉₈N₁₈O₁₉, 1699.8 g/mol; acetate salt: C₆₆H₈₆N₁₈O₁₅, 1371.5 g/mol (PubChem) |
| US FDA approvals | Trelstar 3.75 mg (June 15, 2000), 11.25 mg (June 29, 2001), 22.5 mg (March 10, 2010); Triptodur 22.5 mg (June 29, 2017) |
| Main brands | Trelstar, Triptodur (US); Decapeptyl SR, Gonapeptyl Depot (UK/EU) |
| Route | Intramuscular extended-release microgranule suspension (Trelstar, Triptodur, Decapeptyl SR); intramuscular or subcutaneous depot (Gonapeptyl Depot) |
| Labeled doses (US) | Prostate cancer (Trelstar): 3.75 mg every 4 weeks, 11.25 mg every 12 weeks, or 22.5 mg every 24 weeks. Central precocious puberty (Triptodur): 22.5 mg every 24 weeks |
| Half-life | About 2.8 h terminal half-life after IV bolus in healthy men; depots release peptide over 4, 12, or 24 weeks |
| Key mechanism fact | Transient LH, FSH, and testosterone flare peaking on Days 2–4, followed by pituitary receptor downregulation and castration within 2–4 weeks |
| US status | Prescription-only medication; not a DEA Schedule III controlled substance |
| WADA status | Prohibited at all times in male athletes (Section S2.2.1, testosterone-stimulating peptides in males) |
What it is
Natural GnRH (gonadorelin) is a 10-amino-acid peptide released in short pulses by the hypothalamus. Triptorelin keeps all 10 amino acids of the native sequence except at position 6, where L-glycine is replaced by D-tryptophan (pGlu-His-Trp-Ser-Tyr-D-Trp-Leu-Arg-Pro-Gly-NH₂, or D-Trp⁶-GnRH) (Trelstar label; Lahlou, Ann Urol 2005). That substitution slows cleavage by pituitary peptidases and increases GnRH receptor affinity (Gonapeptyl Depot SmPC).
In rat pituitary cell cultures cited in the US label, triptorelin was 100-fold more active than native GnRH at stimulating LH release and 20-fold more active at displacing radiolabeled GnRH from pituitary receptors; in animal models, triptorelin pamoate showed 13-fold higher LH-releasing and 21-fold higher FSH-releasing activity than native GnRH (Trelstar label). PubChem lists the free base at 1311.4 g/mol (PubChem CID 25074470), the pamoate salt at 1699.8 g/mol (PubChem CID 25074469), and the acetate salt at 1371.5 g/mol (PubChem CID 25080282). Labeled doses are expressed as milligrams of triptorelin free base (Trelstar label).
Approved products and formulations
Because oral triptorelin is digested in the gut, all clinical products are injections. Long-acting depots embed the peptide in biodegradable poly-(D,L-lactide-co-glycolide) (PLGA) microgranules (Trelstar label; Triptodur label).
| Product and region | Salt and matrix | Delivered dose and schedule | Labeled indications |
|---|---|---|---|
| Trelstar (US: NDA 020715, 021288, 022437) | Pamoate in PLGA | 3.75 mg every 4 weeks, 11.25 mg every 12 weeks, or 22.5 mg every 24 weeks IM | Advanced prostate cancer |
| Triptodur (US: NDA 208956) | Pamoate in PLGA | 22.5 mg every 24 weeks IM | Central precocious puberty in patients aged 2 years and older |
| Decapeptyl SR (UK/EU) | Acetate (3 mg) or pamoate (11.25 mg, 22.5 mg) in PLGA | 3 mg every 4 weeks, 11.25 mg every 3 months, or 22.5 mg every 6 months IM | Advanced prostate cancer; endometriosis; uterine fibroids; central precocious puberty; premenopausal breast cancer (3 mg with tamoxifen or exemestane) |
| Gonapeptyl Depot (UK/EU) | Acetate in PLGA syringe | 3.75 mg every 28 days SC or IM (1.875–3.75 mg in children) | Prostate cancer; uterine fibroids; endometriosis; central precocious puberty |
Because the 3.75 mg, 11.25 mg, and 22.5 mg depots use different polymer release matrices, their strengths are not additive, and reconstituted Trelstar suspensions must be injected within 2 minutes (Trelstar label).
Where it sits in the hormone chain
| Compound | Target in the axis | Effect on endogenous testosterone in men |
|---|---|---|
| Kisspeptin-10 | Hypothalamic GnRH neurons | Triggers endogenous GnRH release when pulsed |
| Gonadorelin | Pituitary GnRH receptors (native peptide, half-life 2–3 min IV) | Pulsatile pump dosing stimulates LH and FSH; continuous infusion desensitizes the pituitary |
| Triptorelin and leuprolide | Pituitary GnRH receptors (long-acting superagonists) | Initial 1-week flare in LH, FSH, and testosterone; continuous depot exposure drives testosterone below 50 ng/dL |
| hCG | Testicular Leydig cell LH/CG receptors | Stimulates testicular testosterone directly, bypassing hypothalamus and pituitary |
| Clomiphene and enclomiphene | Hypothalamic and pituitary estrogen receptors | Block estrogen negative feedback to raise endogenous GnRH, LH, and FSH pulses |
Initial hormone flare followed by suppression
Triptorelin produces a biphasic hypothalamic-pituitary-gonadal (HPG) response:
- Initial flare (Days 1–7). Strong binding at pituitary GnRH receptors initially triggers a surge in LH and FSH, raising serum testosterone and dihydrotestosterone in men and estradiol in premenopausal women. Mean serum testosterone peaks on Day 4 after Trelstar 3.75 mg in healthy men, on Days 2 to 3 after 11.25 mg in men with prostate cancer, and on Day 3 after 22.5 mg (Trelstar label).
- Receptor downregulation and castration (Weeks 2–4 onward). Because physiological gonadotropin release requires intermittent GnRH pulses every 60 to 120 minutes, continuous receptor occupancy suppresses transcription of the bioactive LH-beta subunit (Lahlou, Ann Urol 2005). Serum testosterone falls into the castrate range (50 ng/dL or less, or 1.735 nmol/L) by Weeks 3 to 4; in the 22.5 mg trial, geometric mean time to castration was 18.8 days (Trelstar label).
- No acute-on-chronic flare on repeat doses. Once receptors are downregulated, repeat depot injections do not trigger another LH surge: 98.4% of men (124/126) on 3.75 mg had LH of 1.0 IU/L or less 2 hours after their Day 85 injection, and 98.3% on 22.5 mg had no LH rise after their Week 24 injection (Trelstar label; Lundström et al., Clin Drug Investig 2009).
A population PK/PD model of 8 healthy men and 74 prostate cancer patients across 5 formulations estimated a receptor dissociation constant (Kd) of 0.931 ng/mL and found that a serum triptorelin concentration of 0.0609 ng/mL (61 pg/mL) keeps 95% of patients below 50 ng/dL (Romero et al., J Pharmacol Exp Ther 2012).
Pharmacokinetics
After a 0.5 mg intravenous bolus in healthy men, triptorelin follows 3-compartment elimination with distribution half-lives of 6 and 45 minutes, a terminal half-life of 2.81 hours, and a distribution volume of 30 to 33 L without significant plasma protein binding (Müller et al., Br J Clin Pharmacol 1997; Trelstar label). After a 100 µg (0.1 mg) subcutaneous aqueous injection, plasma levels peak at 1.85 ± 0.23 ng/mL at 0.63 hours with an apparent half-life of 7.6 ± 1.6 hours (Decapeptyl SR 3 mg SmPC).
| Group (0.5 mg IV bolus study) | Cmax (ng/mL) | AUCinf (h·ng/mL) | Total clearance (mL/min) | Renal clearance (mL/min) | Terminal half-life (h) |
|---|---|---|---|---|---|
| 6 healthy male volunteers | 48.2 ± 11.8 | 36.1 ± 5.8 | 211.9 ± 31.6 | 90.6 ± 35.3 | 2.81 ± 1.21 |
| 6 men with moderate renal impairment | 45.6 ± 20.5 | 69.9 ± 24.6 | 120.0 ± 45.0 | 23.3 ± 17.6 | 6.56 ± 1.25 |
| 6 men with severe renal impairment | 46.5 ± 14.0 | 88.0 ± 18.4 | 88.6 ± 19.7 | 4.3 ± 2.9 | 7.65 ± 1.25 |
| 6 men with liver disease | 54.1 ± 5.3 | 131.9 ± 18.1 | 57.8 ± 8.0 | 35.9 ± 5.0 | 7.58 ± 1.17 |
In healthy men, 41.7% of an IV dose is excreted intact in urine, while tissue peptidases (pyroglutamyl-peptidase and neutral endopeptidase, not CYP450 enzymes) cleave the rest (Gonapeptyl Depot SmPC). After IM depot injection in prostate cancer patients, mean Cmax is 28.4 ng/mL (3.75 mg), 38.5 ng/mL (11.25 mg), and 44.1 ng/mL (22.5 mg) at 1 to 3 hours, followed by steady release without accumulation (Trelstar label).
What the research shows
Advanced prostate cancer
US approval of the 3 Trelstar depots rested on trials measuring castration (testosterone 50 ng/dL or less) on Day 29 and maintenance from Day 57 onward (Trelstar label; Lundström et al., Clin Drug Investig 2009):
| Trelstar strength and schedule | Evaluable patients | Castrate (50 ng/dL or less) on Day 29 | Maintenance of castration from Day 57 to study end |
|---|---|---|---|
| 3.75 mg every 4 weeks (253-day study) | 137 | 91.2% (125/137); rose to 97.7% by Day 57 | 96.2% (Days 57–253) |
| 11.25 mg every 12 weeks (253-day study) | 171 | 97.7% (167/171) | 94.4% (Days 57–253) |
| 22.5 mg every 24 weeks (337-day study) | 120 | 97.5% (117/120) | 93.3% (112/120, Days 57–337) |
In a pooled analysis of 920 men across 9 prospective trials of the 1-, 3-, and 6-month depots using a stricter threshold of under 20 ng/dL, 79% were below 20 ng/dL at Month 1, 92% at Month 3, 93% at Month 6, and 91% at Month 12, with final median testosterone values of 2.9, 5.0, and 8.7 ng/dL (Breul et al., Adv Ther 2017).
How triptorelin compares with leuprolide
Triptorelin and leuprolide are both GnRH superagonists used for androgen deprivation therapy:
| Feature | Triptorelin (Trelstar, Triptodur, Decapeptyl) | Leuprolide (Lupron Depot, Eligard) |
|---|---|---|
| Structure and weight | Decapeptide (10 amino acids, D-Trp⁶, native Pro⁹-Gly¹⁰-NH₂); 1311.4 g/mol | Nonapeptide (9 amino acids, D-Leu⁶, Pro⁹-N-ethylamide); 1209.4 g/mol |
| US prostate cancer depot doses | 3.75 mg (1-month), 11.25 mg (3-month), 22.5 mg (6-month) IM | 7.5 mg (1-month), 22.5 mg (3-month), 30 mg (4-month), 45 mg (6-month) IM or SC |
| Terminal IV half-life and time to castration | About 2.8 h IV; castrate testosterone in 2–4 weeks | About 3 h IV; castrate testosterone in 2–4 weeks |
In 2 randomized head-to-head trials comparing them in advanced prostate cancer:
- Monthly triptorelin 3.75 mg IM vs leuprolide 7.5 mg IM (n = 284). Over 9 months (253 days), 140 men received triptorelin 3.75 mg and 144 received leuprolide 7.5 mg every 28 days (Heyns et al., BJU Int 2003). Castration on Day 29 was slightly lower with triptorelin (91.2% vs 99.3%; difference −8.0%), but rates matched by Day 57 (97.7% vs 97.1%), cumulative maintenance from Day 29 to Day 253 was 96.2% vs 91.2%, and 9-month secondary overall survival was 97.0% vs 90.5% (P = 0.033).
- Equal 3.75 mg doses IM vs SC (n = 67). When 33 men received 3.75 mg triptorelin IM and 34 received 3.75 mg leuprolide SC every 4 weeks for 3 months, 77% on triptorelin vs 48% on 3.75 mg leuprolide reached testosterone below 1.0 nmol/L (29 ng/dL) at Month 2 (P = 0.02), though US prostate labels use 7.5 mg monthly for leuprolide (Kuhn et al., Eur Urol 1997).
Single-dose hypothalamic-pituitary-gonadal response in men
Because a single aqueous injection of triptorelin clears within hours, it captures the initial agonist flare without lasting long enough to downregulate the pituitary:
- Healthy adult men (1 to 250 µg). In 23 healthy men given single doses of 1 to 50 µg D-Trp⁶-LH-RH (IV, IM, SC, or 8-hour infusion), LH and FSH rose from 2.5 µg upward; a 10 µg bolus matched the peak increment of 100 µg native GnRH, and a 50 µg bolus kept LH and serum testosterone significantly elevated for at least 8 hours (P less than 0.02) (Jaramillo Jaramillo et al., Int J Fertil 1977). After a single 250 µg SC dose in healthy men, serum LH remained elevated at 90 minutes and 24 hours (Mason-Garcia et al., PNAS 1985).
- Diagnostic stimulation test in delayed puberty (0.1 mg SC). Endocrinologists use a single 0.1 mg (100 µg) or 0.1 mg/m² SC dose to distinguish constitutional delay of growth and puberty (CDGP) from isolated hypogonadotropic hypogonadism (IHH) (Ozkan et al., Turk J Pediatr 2001; Binder et al., Clin Endocrinol 2015). In 23 boys aged 14 to 16.5 years, 16 with CDGP and 7 with IHH separated without overlap: 4-hour LH was 33.2 ± 9.3 vs 3.3 ± 2.6 mIU/mL and 24-hour testosterone was 369.3 ± 128.1 vs 61.4 ± 22.6 ng/dL (both P less than 0.0002) (Ozkan et al., Turk J Pediatr 2001). In 61 boys (52 CDGP, 9 IHH), a 4-hour LH peak below 5.3 IU/L after 0.1 mg triptorelin had 100% sensitivity and specificity for IHH (Binder et al., Clin Endocrinol 2015).
- Case report in steroid-induced hypogonadism. A 2010 case report described a 34-year-old bodybuilder with testicular atrophy (2.9 mL) and hypogonadotropic hypogonadism (testosterone 0.3 ng/mL, or 30 ng/dL) 5 months after stopping 13 years of cycling nandrolone, stanozolol, mesterolone, boldenone, clomiphene, and hCG (Pirola et al., Fertil Steril 2010). Given a single 100 µg IV triptorelin diagnostic test, he had a normal LH/FSH surge and his serum testosterone rose to 7.0 ng/mL (700 ng/dL) 10 days later, remaining normal at 1 month. Because a single uncontrolled case cannot distinguish drug effect from spontaneous recovery, 2026 endocrine guidelines state that no controlled clinical trials support GnRH agonists for post-cycle HPG recovery (Smit et al., Endocr Connect 2026; Grant et al., Endocr Connect 2026).
Multi-dose suppression, precocious puberty and estrogen-dependent uses
- Repeated dosing in men. When 8 healthy men received 50 µg/day SC for 6 to 10 weeks, the initial surge gave way by Week 4 to suppressed testosterone, reversible impotence in 5 of 8 men, and sperm counts of 6 million/mL or less in 6 of 8 men (Linde et al., NEJM 1981). A 5-week depot triptorelin study in 10 healthy men reduced testosterone from 7.32 ± 1.92 to 1.15 ± 0.57 ng/mL (P = 0.002) and raised serum leptin from 2.96 to 6.63 ng/mL (P = 0.004) (Hislop et al., Eur J Endocrinol 1999).
- Central precocious puberty and gynecologic/breast indications. In the pivotal US Triptodur trial (44 children aged 2 to 9 years given 22.5 mg every 24 weeks), prepubertal LH suppression (5 IU/L or less) was achieved in 93.2% (41/44) at Month 6 and 97.7% (43/44) at Month 12 (Triptodur label). In Europe and the UK, monthly 3 mg or 3.75 mg depots are used for up to 6 months in endometriosis and uterine fibroids (where bone density drops about 1% per month and menses return 2 to 3 months after the last dose) and for up to 5 years of ovarian suppression with tamoxifen or exemestane in premenopausal breast cancer (SOFT/TEXT trials, n = 4,690) (Decapeptyl SR 3 mg SmPC; Gonapeptyl Depot SmPC).
Side effects and risks
Triptorelin has no FDA boxed warning, but labels warn of effects from both the initial hormone flare and prolonged sex-steroid deprivation (Trelstar label; Triptodur label):
| Trelstar formulation and trial size | Most frequently reported adverse reactions |
|---|---|
| 3.75 mg every 4 weeks (N = 140, treatment-related) | Hot flush 58.6%, skeletal pain 12.1%, impotence 7.1%, headache 5.0%, injection site pain 3.6%, hypertension 3.6% |
| 11.25 mg every 12 weeks (N = 174, treatment-related) | Hot flush 73.0%, skeletal pain 13.2%, headache 6.9%, leg edema 6.3%, leg pain 5.2%, dysuria 4.6%, injection site pain 4.0%, hypertension 4.0% |
| 22.5 mg every 24 weeks (N = 120, treatment-emergent) | Hot flush 72.5%, influenza 15.8%, hypertension 14.2%, urinary tract infection 11.6%, back pain 10.8%, erectile dysfunction 10.0%, testicular atrophy 7.5% |
- Initial tumor flare. During Weeks 1 to 2, the testosterone surge can worsen metastatic bone pain (about 5%) or urinary obstruction (under 2%) and can cause hematuria or spinal cord compression with paralysis in men with vertebral metastases; clinicians may co-administer an antiandrogen such as bicalutamide during the first weeks (Trelstar label; Decapeptyl SR 3 mg SmPC).
- Metabolic, cardiovascular, and bone risks. GnRH agonists increase the risk of hyperglycemia, diabetes, hyperlipidemia, non-alcoholic fatty liver disease, myocardial infarction, sudden cardiac death, stroke, QT/QTc prolongation, and bone loss (in the SOFT/TEXT breast cancer trials, osteoporosis occurred in 39% on triptorelin plus exemestane and 25% on triptorelin plus tamoxifen) (Trelstar label; Decapeptyl SR 3 mg SmPC).
- Rare serious events and contraindications. Labels warn of pituitary apoplexy (sudden pituitary hemorrhage or infarction, usually within 2 weeks of the first dose in patients with an occult pituitary adenoma), severe cutaneous reactions (SJS, TEN, DRESS, AGEP), convulsions, depression or mood changes, and pediatric pseudotumor cerebri (idiopathic intracranial hypertension). Triptorelin is contraindicated in pregnancy, breastfeeding, and hypersensitivity to GnRH analogs, and should not be combined with prolactin-raising drugs (Trelstar label; Triptodur label).
Legal status and sports ban
In the United States, triptorelin (Trelstar, Triptodur) is a prescription-only medication and is not scheduled as a DEA Schedule III controlled substance (21 CFR 1308.13). In competitive sports, the World Anti-Doping Agency (WADA) 2026 Prohibited List bans triptorelin at all times in male athletes under Section S2.2.1 (“Testosterone-stimulating peptides in males”), where triptorelin is explicitly listed alongside leuprolide, gonadorelin, hCG, LH, and kisspeptin (WADA 2026 Prohibited List).
Key takeaways
- A potent decapeptide GnRH superagonist. Replacing glycine at position 6 with D-tryptophan makes triptorelin 100-fold more active than native GnRH at releasing LH in vitro.
- Exposure duration flips the hormonal outcome. A single microgram dose triggers an acute LH, FSH, and testosterone surge over 4 to 24 hours, whereas continuous depot exposure downregulates pituitary GnRH receptors and drives testosterone below 50 ng/dL within 2 to 4 weeks.
- Approved depots span 1, 3, and 6 months. Trelstar (3.75 mg, 11.25 mg, 22.5 mg IM) treats advanced prostate cancer and Triptodur (22.5 mg IM every 24 weeks) treats central precocious puberty in the US; European Decapeptyl and Gonapeptyl labels add endometriosis, uterine fibroids, and premenopausal breast cancer.
- Comparable to leuprolide at 50% of the monthly milligram dose. Monthly triptorelin 3.75 mg matches monthly leuprolide 7.5 mg for castration maintenance by Day 57 (97.7% vs 97.1%) after a slightly slower Day 29 decline (91.2% vs 99.3%).
- Single-dose stimulation is a diagnostic tool, not an approved PCT therapy. Single 100 µg doses distinguish constitutional delayed puberty from hypogonadotropic hypogonadism in boys, and only 1 uncontrolled case report describes a 100 µg diagnostic dose after anabolic steroid use.
- Side effects reflect both flare and castration. Hot flushes affect 58.6% to 73.0% of men on Trelstar, alongside risks of initial tumor flare, bone loss, diabetes, cardiovascular events, QT prolongation, rare pituitary apoplexy, convulsions, and severe skin reactions.
- Banned at all times in male athletes. WADA explicitly lists triptorelin under Section S2.2.1 as a prohibited testosterone-stimulating peptide in males.
Sources
- Verity Pharmaceuticals Inc. Trelstar (triptorelin pamoate for injectable suspension), 3.75 mg, 11.25 mg, and 22.5 mg, prescribing information. DailyMed.
- Azurity Pharmaceuticals Inc. Triptodur (triptorelin for extended-release injectable suspension), 22.5 mg, prescribing information. DailyMed.
- Ipsen Ltd. Decapeptyl SR 3 mg powder and solvent for suspension for injection, Summary of Product Characteristics. emc.
- Ferring Pharmaceuticals Ltd. Gonapeptyl Depot 3.75 mg powder and solvent for suspension for injection, Summary of Product Characteristics. emc.
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- Pirola I, Cappelli C, Delbarba A, et al. Anabolic steroids purchased on the Internet as a cause of prolonged hypogonadotropic hypogonadism. Fertil Steril. 2010;94(6):2331.e1–2331.e3. PubMed.
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- US Code of Federal Regulations. 21 CFR 1308.13, Schedule III. eCFR.
- World Anti-Doping Agency. World Anti-Doping Code International Standard: Prohibited List 2026. WADA 2026 Prohibited List.