Triptorelin
GnRH agonist
Also Trelstar, Triptodur, Decapeptyl, Diphereline, Gonapeptyl, Triptorelin pamoate
- Evidence
- AStrong human evidence
- FDA status
- FDA approvedas of 2026-10-26
- Route
- Injection
- Studies cited
- 1 human0 animal or cell
Sold for
Triptorelin is a long-acting hormone-suppressing injection used for prostate cancer and to pause puberty, and is discussed online as a tool for hormone manipulation.
Studies say
Randomized trials show it drives testosterone to castrate levels as reliably as leuprolide, which supports an A for its approved indications.
Why grade A. Triptorelin's prostate cancer use rests on randomized comparisons with leuprolide, the reference GnRH agonist, including a 2003 BJU International trial of 284 men showing equivalent maintenance of castrate testosterone over nine months. Hormonal suppression is a surrogate endpoint, but it is the accepted basis for approval of this drug class, so it grades A for its approved use. 12
FDA. Triptorelin is approved by the FDA as Trelstar (since 2000) for treatment of advanced prostate cancer, in 1-, 3- and 6-month depot injections, and as Triptodur (2017) for central precocious puberty in children 2 years and older. 23
Written from 3 cited sources. Fact-checked 2026-10-27: 14 claims checked, 3 corrected. Last refreshed 2026-10-27. Not physician reviewed.
Evidence checklist
- Randomised controlled trial Randomized vs leuprolide, 9 monthsyes
- Human study over 100 people 284 men in the leuprolide trialyes
- More than one research group Comparisons plus pediatric studiesyes
- Clinical outcomes, not surrogate markers Testosterone suppression, a surrogate markerno
- Human safety data beyond case reports Hot flashes, bone loss, cardiac warningsyes
Drawn from the cited studies below. A dash means the sources give no information.
What it is
Triptorelin is a 10-amino-acid synthetic analog of gonadotropin-releasing hormone (GnRH), the hypothalamic signal that tells the pituitary to release the hormones (LH and FSH) that drive testosterone and estrogen production. One amino acid is swapped for a D-form, which makes the molecule resist breakdown and bind the receptor more strongly than natural GnRH. It is formulated as microparticles that release the drug over one, three or six months after an intramuscular injection. 2
Trelstar is approved for advanced prostate cancer, where cutting testosterone slows tumor growth. Triptodur treats central precocious puberty, where a child's pituitary switches on too early. Outside the US it is also used for endometriosis, fibroids, breast cancer and in fertility treatment. 23
How it works
Continuous stimulation does the opposite of what pulses do. The pituitary responds to the first dose with a surge of LH and testosterone (the flare), then within two to four weeks its GnRH receptors are desensitized and pulled from the cell surface, LH falls, and the testes stop making testosterone. Levels fall to the castrate range and stay there as long as the depot keeps releasing drug. The initial flare can briefly worsen symptoms in men with bone metastases, which is why an anti-androgen is sometimes given alongside the first injection. 12
What human research shows
In the 2003 BJU International trial, 284 men with advanced prostate cancer were randomized to monthly triptorelin or monthly leuprolide for nine months. Castrate testosterone was reached by 91 percent of triptorelin patients at day 29 compared with 99 percent on leuprolide, but by day 57 the two were equivalent (98 percent and 97 percent), and maintenance of castration from day 29 to day 253 was equivalent. Nine-month survival was 97 percent with triptorelin and 90.5 percent with leuprolide. 1
The 6-month depot was approved for prostate cancer and, as Triptodur, for central precocious puberty on the basis of a single-arm open-label study in 44 children aged 2 to 9, where LH was suppressed to prepubertal levels in the large majority of treated patients. 23
| Study | Model | Finding |
|---|---|---|
| Heyns 2003 (BJU International) | Humans, n=284 men with advanced prostate cancer, randomized comparison with leuprolide, 9 months | Castration was reached slightly more slowly with triptorelin but maintained equivalently from day 29 to day 253; nine-month survival was higher with triptorelin. 1 |
| Trelstar prescribing information | FDA label, pooled trials | Approved indication, formulation strengths, hormone-flare and class warnings. 2 |
Safety
The side effects are those of testosterone or estrogen deprivation: hot flashes in roughly half of men, erectile dysfunction, loss of libido, fatigue, and over time loss of bone density and muscle. Injection-site pain is common. The transient hormone flare after the first dose can cause bone pain or, rarely, spinal cord compression or urinary obstruction in men with metastases. 12
The label warns of increased risk of diabetes and cardiovascular events with androgen deprivation therapy as a class, QT interval prolongation on the ECG, and rare pituitary apoplexy (sudden bleeding into a pituitary tumor). In children, Triptodur carries warnings about psychiatric symptoms and seizures reported with GnRH agonists. 23
Questions for your clinician
- How will my bone density and heart health be monitored during treatment?
- What should I watch for in the first weeks after the first dose?
- Which depot interval fits my care plan?
Questions people ask
Is triptorelin FDA-approved?
Yes. Trelstar was approved in 2000 for advanced prostate cancer and comes in 1-, 3- and 6-month depot injections. Triptodur, a 6-month formulation, was approved in 2017 for central precocious puberty. 23
How does triptorelin differ from leuprolide?
They are both GnRH agonists with the same mechanism and similar efficacy. In a 284-man randomized trial, triptorelin took slightly longer to bring testosterone to castrate levels but maintained suppression equally well over nine months. 1
Why does testosterone rise before it falls?
Triptorelin is an agonist: the first dose stimulates the pituitary and testosterone surges for a week or two. Only with continuous exposure do the receptors shut down and testosterone collapse. This flare is why some men receive an anti-androgen at the start. 12
Which adverse effects come up most?
Those of low testosterone or estrogen: hot flashes, sexual dysfunction, fatigue, and bone loss with long use. Class warnings include diabetes, cardiovascular events and QT prolongation. 2
Citations
- Heyns 2003, BJU Int: Comparative efficacy of triptorelin pamoate and leuprolide acetate in men with advanced prostate cancer doi.org
- FDA 2026: Trelstar (triptorelin pamoate) prescribing information accessdata.fda.gov
- FDA 2017: Triptodur (triptorelin) extended-release injectable suspension prescribing information accessdata.fda.gov