Also known as: Decapeptyl, Trelstar, GnRH Agonist
Half-life: ~3 hours (aqueous); weeks (depot formulation)
Last reviewed: · Published:
Triptorelin is a synthetic decapeptide analog of gonadotropin-releasing hormone (GnRH) with a single amino acid substitution (D-tryptophan at position 6) that confers dramatically increased receptor binding affinity and resistance to enzymatic degradation. Because it is a long-acting GnRH receptor agonist, Triptorelin's effect on the hypothalamic-pituitary-gonadal (HPG) axis is biphasic: an initial "flare" of LH/FSH release and consequent rise in sex hormones lasting 1-2 weeks, followed by sustained receptor desensitization that suppresses gonadotropin release and produces a state of "medical castration" with sustained dosing.
Clinically, Triptorelin (brand names Decapeptyl, Trelstar, Diphereline) is FDA-approved as a long-acting depot injection for the treatment of advanced prostate cancer, where the sustained suppression of testosterone is therapeutic. It is also used for endometriosis, uterine fibroids, precocious puberty, and as part of IVF protocols.
In the bodybuilding and self-experimentation community, Triptorelin is used in a very different way: as a single low-dose injection at the end of an anabolic steroid cycle to leverage the initial "flare" of LH release for HPG axis restart (post-cycle therapy / PCT). This use leverages only the first part of Triptorelin's biphasic effect; chronic dosing in this context would produce the opposite of the desired effect by suppressing the HPG axis. A single 100-200 mcg injection is the typical PCT protocol. Long-term safety of this off-label use is reasonable to extrapolate from the much higher chronic doses used clinically, but the protocol itself is unstudied.
Triptorelin was developed in the early 1980s by Tulane University researchers (Andrew V. Schally's group, building on their Nobel Prize-winning GnRH work) and licensed to Ipsen for clinical development. The depot formulation (Decapeptyl LA) was approved for prostate cancer in Europe in the late 1980s and in the US (as Trelstar) in 2000. Subsequent approvals extended use to other gonadotropin-dependent conditions including endometriosis and precocious puberty.
Chronic clinical Triptorelin use produces the constellation of effects associated with castration-level testosterone suppression — hot flashes, libido loss, mood changes, and (with prolonged use) bone density loss. Single low-dose PCT use does not produce this side-effect profile because the chronic suppression phase is never reached; the main effects in PCT use are the headache and mild flu-like feelings sometimes associated with the acute LH surge. The single-dose PCT protocol has been used widely in self-experimentation for over a decade with no major safety signals reported, but lacks formal clinical study.
Dose Range
100-200 mcg
Frequency
Single dose at cycle end (SubQ)
Duration
One-time
Dose Range
3.75 mg / 11.25 mg / 22.5 mg
Frequency
Monthly / quarterly / semi-annual depot IM
Duration
Long-term
Dose Range
3.75 mg monthly depot IM
Frequency
Monthly
Duration
3-6 months typical
Dosing information is for educational purposes only. Consult a healthcare professional before using any peptide.
Typical Vial Size
2 mg
Water Type
Bacteriostatic water (BAC water) for research/PCT use; clinical depot has specific reconstitution
Mixing Volume
1-2 mL
Half-Life
~3 hours (aqueous); weeks (depot formulation)
Molecular Weight
1,311 Da
Store reconstituted vial refrigerated at 2-8°C. Use within 14-21 days. Clinical depot formulations have their own reconstitution and are designed for sustained release; PCT use of research-grade peptide is aqueous SubQ single-injection.
FDA Status
FDA approved (Trelstar) for advanced prostate cancer. Other indications approved internationally (Decapeptyl, Diphereline).
Legal Status
Prescription drug in clinical formulations. Research chemical in vendor-sold form. Prohibited by WADA.
USA
Approved (Trelstar)Advanced prostate cancer; depot IM
EU
Approved (Decapeptyl)Prostate cancer, endometriosis, fibroids, precocious puberty
UK
Approved (Decapeptyl)Multiple gonadotropin-dependent indications
Australia
Approved (Decapeptyl)Prostate cancer, endometriosis
Canada
Approved (Trelstar)Prostate cancer; depot IM
Lambertini M, Boni L, Michelotti A, Gamucci T, Scotto T, Gori S, Giordano M, Garrone O, Levaggi A, Poggio F, Giraudi S, Bighin C, Vecchio C, Sertoli MR, Pronzato P, Del Mastro L
Drugs (2014)
Comprehensive review of Triptorelin's clinical pharmacology and use across multiple gonadotropin-dependent conditions, providing the clinical foundation that informs off-label PCT applications.
View Study →Crowley WF Jr, Comite F, Vale W, Rivier J, Loriaux DL, Cutler GB Jr
Journal of Clinical Endocrinology & Metabolism (1981)
Foundational human pharmacology study showing that single-dose GnRH agonist administration produces a reliable initial gonadotropin surge with subsequent recovery — the pharmacology underlying the off-label PCT use of low-dose Triptorelin.
View Study →Conn PM, Crowley WF Jr
Annual Review of Medicine (1994)
Classic mechanistic review of GnRH analog pharmacology including the biphasic flare-then-suppression response that defines both the clinical and off-label uses of Triptorelin and related compounds.
View Study →Track Triptorelin and more with PinnyPeptide.
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