What the human research shows
Two pages' worth of evidence under one name. The licensed uses are grade A: decades of use, large approval programmes, three depot intervals on the label. The "HPTA restart" use that brings people to this page is grade D — one case report, n=1, and a mechanism that cuts the other way if the dose is wrong.
Evidence profile0–5
- Metabolic & weight—0.0
- Cardiovascular—0.0
- Muscle & growth—0.0
- Healing & repair—0.0
- Neuro & sleep—0.0
- Immune & inflammation—0.0
- Sexual & hormonalA5.0
- Skin & appearance—0.0
- Ageing & longevity—0.0
| Outcome | Grade | Effect size | Human studies | Where the evidence comes from |
|---|---|---|---|---|
| Testosterone suppression in advanced prostate cancer | AEstablished | Large | Approval programme; decades of use | The licensed indication. Continuous GnRH receptor occupancy desensitises the pituitary, and after a transient surge testosterone falls to castrate levels. The Trelstar label carries three depot intervals for this use and the effect is the basis of forty years of androgen-deprivation therapy.1 |
| Central precocious puberty | AEstablished | Large | Approval programme | Triptodur is approved for central precocious puberty in children aged two and above, as a single depot injection repeated every 24 weeks — the same axis shutdown used to halt premature puberty.2 |
| Restarting testosterone after anabolic steroids | DNo human evidence | Not measurable | 1 case report (n=1) | A 2010 Italian case report describes one man with hypogonadism after anabolic steroid use who was given a single 100 μg dose of triptorelin; testosterone was in the normal range within a month. One patient, no control, no replication in sixteen years. Forum protocols built on this report also ignore the dose relationship: the licensed depot products use the same molecule to switch the axis off.3 |
| Initial testosterone surge ("flare")adverse | AEstablished | Moderate | Approval programme | The first days after a depot injection bring a rise in testosterone before suppression — clinically important in prostate cancer because it can transiently worsen symptoms, and the reason anti-androgen cover is used.1 |
Literature searched to 29 October 2026. Human studies only; animal and cell work informs the mechanism section and nothing else.
Registered trials
ClinicalTrials.gov lists 110+ interventional studies naming Triptorelin as an intervention — 50 completed, 12 recruiting, and 24 with results posted to the registry.
A registration is not a result. Anyone can register a study, and many never report — so this list shows what has been attempted, not what has been shown. The graded evidence above is the answer to whether something works.
102 further studies are registered. Participant counts marked * are the sponsor's estimate, not a final enrolment. Source: ClinicalTrials.gov, read directly from the registry and refreshed weekly.
What it is
Triptorelin is GnRH with one substitution: the glycine at position six is replaced by D-tryptophan, which resists the enzymes that destroy the natural hormone in minutes. The Trelstar label gives the structure as a synthetic decapeptide. The result is a molecule that occupies the receptor long enough to desensitise it — the same trick leuprolide uses, from the same era.
It is supplied as a depot suspension for intramuscular injection in several intervals. The grey-market product sold as a single-use vial for "restart" protocols is a different preparation from the licensed depots, and in most of LYO's regions selling it for human use without authorisation is unlawful.
How it is thought to work
Pulsed GnRH keeps the pituitary releasing LH and FSH; GnRH present continuously desensitises the receptor and stops them. Triptorelin's long action makes it a continuous signal, which is why it suppresses. The restart idea uses the opposite end of the curve: a single small dose as one artificial pulse, intended to prompt one burst of LH and FSH and so restart a suppressed axis. The pharmacology of that is coherent; the human evidence for it is one man.
What is still unknown
- Whether a single low dose restarts the axis in anyone other than the one reported patient — no trial has tested it.
- What dose, if any, produces a pulse rather than the beginning of suppression.
- Whether the case report's outcome would have occurred spontaneously, as post-steroid hypogonadism often resolves without treatment.
The molecule and how long it lasts
- Formula
- C64H82N18O13
- Molecular weight
- 1311.4 g/mol
- CAS number
- 57773-63-4
- PubChem
- CID 25074470
- Sequence
- [pGlu]HWSY[D-Trp]LRPG-NH2
Matches the decapeptide structure given in the Trelstar label.
PubChem record, read 29 October 2026; the sequence was derived from that record's own structure and checked against the product label where one exists.
- Route
- Intramuscular depot injection
- Half-life
- About 6 minutes, 45 minutes and 3 hours in a three-compartment model
- Licensed regimen (Trelstar)
- Depot injection repeated every 4, 12 or 24 weeks depending on the strength used, for advanced prostate cancer; Triptodur is a 24-week depot for central precocious puberty
From the approved product's prescribing information: Trelstar prescribing information (DailyMed) The regimen is the label's own wording, reproduced as a regulatory fact.
Regulatory status
Authorised nationally across member states (Decapeptyl and others) for prostate cancer, endometriosis, uterine fibroids, precocious puberty and in assisted reproduction.
Trelstar for advanced prostate cancer; Triptodur for central precocious puberty. Vials sold online for "restart" protocols are unapproved drugs.
Decapeptyl SR licensed by the MHRA.
Diphereline / Decapeptyl registered on the ARTG.
Trelstar authorised with a Drug Identification Number.
GnRH agonists are S2 (peptide hormones, growth factors and related substances) for male athletes.
Questions people actually ask
Does a single triptorelin shot restart testosterone after a steroid cycle?
Is triptorelin the same as leuprolide?
Is triptorelin banned in sport?
One page per claimed effect
- ADoes Triptorelin help with testosterone suppression in advanced prostate cancer?Approval programme; decades of use
- ADoes Triptorelin help with central precocious puberty?Approval programme
- DDoes Triptorelin help with restarting testosterone after anabolic steroids?1 case report (n=1)
- AHow common is initial testosterone surge with Triptorelin?Approval programme
References
- 1Trelstar (triptorelin pamoate) prescribing information.DailyMed, read 29 Oct 2026Advanced prostate cancer; three depot intervals; pharmacokinetics and the decapeptide structure.
- 2Triptodur (triptorelin) prescribing information.DailyMed, read 29 Oct 2026Central precocious puberty in children aged 2 and above; 24-week depot.
- 3Pirola I, Cappelli C, Delbarba A, et al. Anabolic steroids purchased on the Internet as a cause of prolonged hypogonadotropic hypogonadism.Fertil Steril, 2010;94:2331–2332Case report, n=1. The origin of the "triptorelin restart" protocol.
Change log
- 2026-10-29Initial publication. Grade A for the licensed uses; the grey-market restart row graded D on a single case report.