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FDA-approvedVendors pendingFacts verified · 2026-05-25

Triptorelin

Also known as [d-trp6]-gnrh, decapeptyl · Wikipedia

Triptorelin (Trelstar, Decapeptyl) is an FDA-approved synthetic decapeptide GnRH (LHRH) agonist with a D-Trp6 substitution that confers roughly 100-fold greater potency than native GnRH and resistance to enzymatic degradation. In the US, Trelstar pamoate intramuscular depot is approved for the palliative treatment of advanced prostate cancer, with 1-, 3-, and 6-month formulations (3.75 mg, 11.25 mg, 22.5 mg). In Europe and elsewhere, additional formulations are approved for endometriosis, uterine fibroids, central precocious puberty, and adjunctive therapy in premenopausal hormone-receptor-positive breast cancer. Triptorelin is widely misused off-label as a research-chemical 'PCT' agent without supporting clinical evidence.

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Mechanism of action

Triptorelin (pGlu-His-Trp-Ser-Tyr-D-Trp-Leu-Arg-Pro-Gly-NH2) is a synthetic decapeptide GnRH agonist with a D-Trp at position 6 that confers ~100-fold greater receptor potency and resistance to peptidase cleavage relative to native GnRH. Acute administration produces a transient LH/FSH and testosterone (or estradiol) surge - the 'flare' effect.

Triptorelin (pGlu-His-Trp-Ser-Tyr-D-Trp-Leu-Arg-Pro-Gly-NH2) is a synthetic decapeptide GnRH agonist with a D-Trp at position 6 that confers ~100-fold greater receptor potency and resistance to peptidase cleavage relative to native GnRH. Acute administration produces a transient LH/FSH and testosterone (or estradiol) surge - the 'flare' effect. Continuous occupancy of pituitary GnRH receptors via the depot pamoate microsphere formulation down-regulates and desensitises the receptors, suppressing pulsatile LH and FSH secretion and driving gonadal steroidogenesis to medical-castration levels within 2-4 weeks (Lepor and Shore, Rev Urol 2012). Recovery of HPG axis function after depot discontinuation is slow and incomplete in older patients. The pamoate microsphere formulation provides sustained release over 1, 3, or 6 months.

Pharmacokinetic properties

Half-life

After IV bolus, three-compartment model with terminal half-lives ~6 min, ~45 min, ~3 hours. Depot formulation (Trelstar pamoate IM) provides sustained release over 1-6 months depending on dose strength.

Routes

intramuscular · subcutaneous

Bioavailability

Trelstar approved formulation is IM only as pamoate microsphere depot. Other formulations (acetate) available outside US as SC. Oral bioavailability negligible.

Amino-acid sequence

pGlu-His-Trp-Ser-Tyr-D-Trp-Leu-Arg-Pro-Gly-NH2

Use & research dosing

HPG Axis ModulationResearch Agonist

FDA-approved Trelstar pamoate dosing for advanced prostate cancer: 3.75 mg IM every 4 weeks, 11.25 mg IM every 12 weeks, or 22.5 mg IM every 24 weeks (Trelstar US prescribing information). Lower doses are used for paediatric central precocious puberty and gynecologic indications outside the US. Off-label 'post-cycle therapy' use in research-chemical communities (typically a single 100-mcg dose) is not approved, has no controlled clinical evidence base, and misunderstands the mechanism - acute exposure produces only the transient flare, then suppression.

Research-use framing only. SavePeptides sells nothing for human consumption. Doses above reflect reported research / self-experimentation ranges, not clinical recommendations.

Editorial perspective

Triptorelin is the mechanistic opposite of pulsatile gonadorelin despite sharing the same GnRH receptor target: continuous occupancy via depot formulation suppresses, rather than stimulates, the HPG axis. Using triptorelin for 'testicular preservation' on TRT would do the opposite of what is intended. The off-label 'single-dose PCT' protocol popular in research-chemical communities lacks any controlled clinical evidence and could induce a prolonged suppressive phase rather than recovery. Trelstar is the FDA-approved brand.

— SavePeptides editorial desk · last updated 2026-05-25

Cautions & contraindications

Before researching this compound, note:

  • Testosterone (or estradiol) flare in the first 1-2 weeks can transiently worsen prostate-cancer symptoms (spinal-cord compression, ureteral obstruction, bone pain) - often co-administered with an antiandrogen
  • Pregnancy Category X - causes fetal harm; effective contraception required
  • Bone mineral density loss with long-term androgen/oestrogen suppression - monitor DEXA, consider bisphosphonates or denosumab
  • Cardiovascular risk signal (MI, stroke, sudden death) with the GnRH-agonist drug class
  • QT interval prolongation reported - caution with other QT-prolonging drugs and in congenital long-QT
  • New-onset or worsening diabetes and hyperglycaemia reported
  • Hypogonadal symptoms: hot flashes, libido loss, erectile dysfunction, mood changes, fatigue
  • Hypersensitivity reactions including anaphylaxis reported (rare)
  • Injection-site reactions; depot bead may cause sterile abscess in rare cases
  • Off-label 'PCT' use lacks evidence and may further suppress, not restore, the HPG axis

Research foundation

The papers behind the page.

  1. [01]https://www.accessdata.fda.gov/drugsatfda_docs/label/2023/020715s045,021288s040,022437s020lbl.pdf
  2. [02]https://pubmed.ncbi.nlm.nih.gov/27246172/

Facts verified

2026-05-25

Confidence

high

What this means

  • FDA-approved drug (Trelstar) for advanced prostate cancer
  • off-label single-dose 'PCT' use has no controlled clinical evidence
  • testosterone flare in first 1-2 weeks - co-administered antiandrogen often required in prostate cancer

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