A tier · strong
Triptorelin holds live UK marketing authorisations as a prescription-only medicine (Decapeptyl SR, Ipsen, PL 34926/0002; Gonapeptyl Depot, Ferring, PL 03194/0085) with five live emc SmPCs in total, and has been approved in the United States since 2000, across prostate cancer, endometriosis, uterine fibroids, early breast cancer, central precocious puberty and the reduction of testosterone to castrate levels in severe sexual deviation. It stops short of S because its registration trials are in the hundreds rather than the multi-thousands, and because zero of the 294 registered triptorelin studies address the use the research market actually sells it for.
triptorelin
Triptorelin is a synthetic decapeptide GnRH agonist made resistant to degradation and far more potent than native GnRH by substituting D-tryptophan at position 6. A single exposure produces an acute pituitary gonadotrophin surge, while continued exposure desensitises and downregulates GnRH receptors, suppressing LH and FSH and driving gonadal steroid output to castrate levels. It is a licensed prescription-only medicine in the UK and the US, used in hormone-dependent prostate cancer, endometriosis, uterine fibroids, early breast cancer, central precocious puberty, and — under the brand Salvacyl — the deliberate reduction of testosterone to castrate levels in men with severe sexual deviations.
the explanation
Triptorelin is a lab-made copy of the brain hormone that tells the pituitary gland to switch the sex hormones on. Used continuously it does the opposite: the pituitary is overwhelmed, stops responding, and sex hormone levels fall almost to zero. That is exactly why doctors use it for prostate cancer, endometriosis, fibroids and children whose puberty starts far too early, and it is also why using it to 'restart' testosterone after a steroid cycle works against the drug's own pharmacology.
regulatory status
Licensed prescription-only medicine in the UK; US-approved since 2000
Triptorelin holds multiple live UK marketing authorisations, all prescription-only. Decapeptyl SR (Ipsen Limited, PL 34926/0002; SmPC text revised 1 June 2026) is indicated in locally advanced and metastatic hormone-dependent prostate cancer, as adjuvant and neoadjuvant therapy with radiotherapy in high-risk disease and after radical prostatectomy, in endometriosis, in uterine fibroids, and in early-stage breast cancer in premenopausal women alongside tamoxifen or an aromatase inhibitor. Gonapeptyl Depot (Ferring Pharmaceuticals Ltd, PL 03194/0085; revised 2 December 2024) is likewise prescription-only and adds confirmed central precocious puberty in girls under 9 and boys under 10. Salvacyl (Ipsen Limited, PL 034926/0012; revised 9 June 2025) is a third prescription-only UK triptorelin product, licensed for the reversible reduction of testosterone to castrate levels in order to decrease sexual drive in adult men with severe sexual deviations, to be initiated by a psychiatrist alongside psychotherapy. All five triptorelin products on the emc are depot formulations. In the United States triptorelin carries an initial approval date of 2000 and is marketed as TRELSTAR for advanced prostate cancer and as TRIPTODUR for central precocious puberty in patients aged 2 years and older. In the EU triptorelin is authorised nationally rather than through a centralised EMA marketing authorisation. It is not a controlled drug and is not a lawful dietary-supplement ingredient. Section S2.2.1 of the WADA 2026 Prohibited List names triptorelin explicitly among GnRH and its agonist analogues, grouped under testosterone-stimulating peptides in males and prohibited at all times.
how it works · proposed mechanism
Triptorelin is a GnRH receptor superagonist, and everything clinically interesting about it follows from the difference between pulsatile and continuous receptor occupancy. The native hypothalamic signal is pulsatile, and the pituitary responds to pulses; a long-acting agonist replaces pulses with continuous stimulation, and the gonadotroph responds by shutting down. Both phases — the initial flare and the subsequent suppression — are documented in the licensed product information.
Superagonism at the pituitary GnRH receptor
Replacing glycine at position 6 with D-tryptophan slows enzymatic degradation and increases receptor affinity, so triptorelin occupies the GnRH receptor far longer than the native decapeptide. The pharmacological target is the pituitary gonadotroph, not the gonad.
The acute flare, and its one legitimate single-exposure use
A single triptorelin exposure transiently raises LH and FSH. This is the basis of the triptorelin stimulation test: in a prospective study of boys with delayed puberty, the four-hour LH response after testosterone priming and withdrawal discriminated constitutional delay from isolated hypogonadotrophic hypogonadism with 93% sensitivity and 100% specificity. That is a diagnostic application, not a therapeutic one.
Desensitisation and downregulation
The UK SmPC states that continued administration beyond about a week leads to suppression of gonadotrophins and a consequent fall in plasma testosterone. This suppression, not the flare, is the therapeutic effect in prostate cancer, endometriosis, fibroids and precocious puberty.
Why the depot formulation dismantles the post-cycle claim
Every licensed triptorelin product is a sustained-release microsphere depot designed to hold exposure steady for weeks. Sustained exposure is the suppressive condition. A protocol built on repeating the flare is fighting the formulation and the receptor biology simultaneously, and no trial has ever tested whether it achieves anything.
what’s reported
evidence shape
7 sourcesThe composition of the cited literature by study type. This describes the shape of the evidence, not its quality — and it does not by itself set the grade.
⚠ the catch
Triptorelin grades A on an oncology and gynaecology evidence base that has nothing to do with why it is sold in the research-peptide market. The market sells it as a post-cycle 'testosterone restart', but the licensed pharmacology runs the other way: the UK SmPC states plainly that continued administration leads to suppression of gonadotrophins and a fall in plasma testosterone, and every licensed product is a depot engineered to sustain exactly that suppressive exposure for weeks. The clearest illustration is that the MHRA has licensed triptorelin under a third brand, Salvacyl, specifically for the reversible reduction of testosterone to castrate levels in men with severe sexual deviations — the same molecule, in the same country, licensed to do the exact opposite of what it is being sold to do. The only well-characterised single-exposure use in men is diagnostic — a four-hour LH response that separated constitutional pubertal delay from isolated hypogonadotrophic hypogonadism with 93% sensitivity and 100% specificity — not therapeutic. A targeted ClinicalTrials.gov search across the 294 registered triptorelin studies returns three records touching hypogonadism or steroid exposure, and all three are diagnostic or IVF studies; not one tests recovery after anabolic-androgenic steroid use. The strongest thing the market can point to is a cross-sectional survey of 470 men reporting that post-cycle therapy in general felt better than nothing, which is not evidence about triptorelin and not evidence about testosterone recovery.
key published findings
- Decapeptyl SR (Ipsen, PL 34926/0002; SmPC revised 1 June 2026) states its legal category as 'Prescription only medicine' and its section 4.1 indications are locally advanced and metastatic prostate cancer, adjuvant and neoadjuvant use with radiotherapy and after radical prostatectomy, endometriosis, uterine fibroids, and early-stage breast cancer in premenopausal women.
- Gonapeptyl Depot (Ferring, PL 03194/0085; revised 2 December 2024) is also prescription-only and additionally covers confirmed central precocious puberty in girls under 9 and boys under 10, while Salvacyl (Ipsen, PL 034926/0012; revised 9 June 2025) is licensed for 'the reversible reduction of testosterone to castrate levels in order to decrease sexual drive in adult men with severe sexual deviations' — the same molecule the research market sells as a testosterone restart.
- Section 5.1 of the UK SmPC states that continued administration leads to suppression of gonadotrophins and a consequent fall in plasma testosterone — the licensed pharmacology is suppressive, not restorative.
- In a prospective study of boys with delayed puberty, the four-hour LH response to a single triptorelin challenge after testosterone priming and withdrawal discriminated constitutional delay from isolated hypogonadotrophic hypogonadism with 93% sensitivity and 100% specificity.
- A ClinicalTrials.gov search for triptorelin combined with hypogonadism or anabolic-steroid terms returns three records — an iatrogenic-hypogonadism MRI substudy (NCT02102646, 31 participants), a diagnostic study in hypogonadotrophic hypogonadism (NCT06691815, 48 participants) and an IVF study (NCT02674178, 235 participants) — none of which tests post-cycle recovery.
- In a survey of 470 men who had used anabolic-androgenic steroids, 95.1% reported withdrawal symptoms on cessation, and self-reported post-cycle therapy use was associated with roughly 60% reductions in cravings and withdrawal symptoms and about 50% in suicidal thoughts — cross-sectional self-report, not triptorelin-specific, and not a controlled comparison.
limitations of the evidence
- No randomised controlled trial has tested triptorelin for restoring endogenous testosterone production after exogenous androgen use, in any population.
- The pharmacology points the wrong way for the marketed purpose: sustained GnRH receptor occupancy desensitises and downregulates the receptor and suppresses the axis, which is why the same molecule is used to induce medical castration in prostate cancer.
- Every licensed presentation is a sustained-release depot, so the formulation available in the legitimate supply chain is designed to deliver the suppressive rather than the stimulatory exposure profile.
- The best human data on single-exposure triptorelin are diagnostic accuracy studies in adolescents with delayed puberty, which say nothing about therapeutic outcomes in adults recovering from androgen use.
- The survey evidence the market leans on is about post-cycle therapy as a general practice, is self-reported, has no control group, and does not isolate triptorelin from hCG, clomiphene or tamoxifen.
- As a prescription-only medicine, triptorelin sold as a research chemical carries none of the identity, potency or sterility assurance attached to a marketing authorisation, and depot pharmacology means an error in exposure cannot be withdrawn once given.
documented safety signals
- The initial gonadotrophin surge is a labelled hazard, not an incidental effect: the UK SmPC records initial stimulation of pituitary gonadotrophin release before suppression develops, and the US TRIPTODUR prescribing information lists an initial rise in sex hormone levels among its warnings and precautions.
- The TRIPTODUR label carries warnings and precautions for psychiatric events, convulsions, severe cutaneous adverse reactions and pseudotumor cerebri (idiopathic intracranial hypertension). There is no boxed warning.
- Sustained gonadotrophin suppression produces a hypogonadal state that is the therapeutic goal in prostate cancer but the precise outcome someone using triptorelin for 'recovery' is trying to avoid.
- Because no trial has studied triptorelin in androgen-withdrawal states, the risk that it prolongs rather than shortens hypogonadal recovery is entirely unquantified.
identity
| full name | Triptorelin, a synthetic decapeptide gonadotrophin-releasing hormone (GnRH/LHRH) agonist in which glycine at position 6 is replaced by D-tryptophan |
| category | Ancillary & Endocrine |
| modality | peptide |
| formula | C64H82N18O13 |
| molar mass | 1311.4 g/mol |
| cas | 57773-63-4 |
| half-life | Biological half-life of about 7.6 hours in healthy volunteers and about 11.7 hours in men with prostate cancer for the immediate-release subcutaneous form; the licensed depot presentations release triptorelin gradually over weeks and are not described by a simple half-life |
| sequence | pGlu-His-Trp-Ser-Tyr-D-Trp-Leu-Arg-Pro-Gly-NH2 |
laboratory handling
| storage | Handle the lyophilised peptide as a hygroscopic, light-sensitive solid: store the sealed vial frozen and desiccated, protected from light, and allow it to reach room temperature before opening so moisture does not condense on the powder. Aqueous solutions are less stable than the lyophilisate; hold them refrigerated between 2 °C and 8 °C, protect from light, aliquot on first reconstitution and avoid repeated freeze-thaw cycles. Licensed depot presentations are stored per their own product information and must not be inferred from research-reagent handling. |
| solubility | Soluble in water and in aqueous buffers; the acetate salt is markedly more water-soluble than the pamoate, which is deliberately poorly soluble to serve as a depot. Mildly acidic aqueous buffers are used for the immediate-release salt. Avoid strongly alkaline conditions, and be aware that the tryptophan residues make the molecule sensitive to light and to oxidising conditions. |
| co-studied with | Post-cycle protocols circulating in the market pair triptorelin with hCG, clomiphene or tamoxifen; no controlled study has tested any of those combinations, and adding a sustained-exposure GnRH agonist to an axis one is trying to restart is pharmacologically self-defeating. |
Handling information describes laboratory practice for a research reagent. It is not a preparation guide for use in humans.
the receipts
7 citedelectronic medicines compendium (emc) · 2026 · official
electronic medicines compendium (emc) · 2024 · official
US Food and Drug Administration, Drugs@FDA · 2025 · official
World Anti-Doping Agency · 2026 · official
electronic medicines compendium (emc) · 2025 · official
Clinical Endocrinology (Oxford) 86(5):717-724 · 2017 · clinical study
Substance Abuse Treatment, Prevention, and Policy 18(1):66 · 2023 · observational
others in Ancillary & Endocrine