Triptorelin Evidence Guide
Triptorelin (Trelstar) is FDA-approved for prostate cancer androgen deprivation and gender-affirming hormone therapy, with multiple Phase 3 RCTs supporting both indications. As a GnRH agonist, it produces reliable castrate-level testosterone suppression with a well-characterized adverse effect profile. For research into GnRH agonist pharmacology or testosterone suppression, it is a validated reference compound.
Our Take
Triptorelin (Trelstar) is FDA-approved for prostate cancer androgen deprivation and gender-affirming hormone therapy, with multiple Phase 3 RCTs supporting both indications. As a GnRH agonist, it produces reliable castrate-level testosterone suppression with a well-characterized adverse effect profile. For research into GnRH agonist pharmacology or testosterone suppression, it is a validated reference compound.
- Best for
- Prostate cancer androgen deprivation, gender-affirming hormone therapy, GnRH agonist pharmacology
- Evidence grade
- Level A
- Confidence
- High
- Starting point
- 3.75mg IM monthly or 11.25mg IM every 3 months
Benefits and Evidence
- Prostate Cancer Control: Level A, includes human evidence - Triptorelin achieves castrate testosterone levels in >95% of advanced prostate cancer patients. Multiple large RCTs demonstrate disease control equivalent to surgical castration with reversibility.
- Endometriosis Symptom Relief: Level A, includes human evidence - Significant reduction in endometriosis-related pain, dysmenorrhea, and endometrial implant size. Efficacy comparable to other GnRH agonists with estrogen suppression.
- Central Precocious Puberty Arrest: Level A, includes human evidence - Effectively halts premature pubertal development and preserves adult height potential. Standard of care for central precocious puberty in children.
Side Effects and Warnings
- Hot flashes
- Initial tumor flare (prostate cancer)
- Decreased libido and erectile dysfunction
- Bone mineral density loss with prolonged use
- Injection site reactions
- Mood changes and depression
- Fatigue
- Initial testosterone flare can worsen prostate cancer symptoms - consider anti-androgen cover for first 2-4 weeks
Research Dosage References
- <strong>Intramuscular depot</strong> - 3.75 mg (monthly) or 11.25 mg (3-month) or 22.5 mg (6-month) - Monthly, quarterly, or semi-annually - Depot formulation provides sustained release. Prostate cancer: typically 3-month or 6-month depot. Endometriosis: usually limited to 6 months with add-back therapy.
- <strong>Subcutaneous</strong> - 0.1 mg/day - Daily (short protocol for IVF) - Used in some IVF stimulation protocols. Less common than depot formulations.
Mechanism of Action
Triptorelin acts through GnRH receptor desensitization: 1. Initial agonism: Binds GnRH receptors on pituitary gonadotropes with high affinity, initially stimulating LH and FSH release ("flare" effect lasting 1-2 weeks). 2. Receptor downregulation: Continuous receptor occupation leads to internalization and downregulation of GnRH receptors on the cell surface. 3. Gonadotropin suppression: Desensitized pituitary stops producing LH and FSH, leading to profound suppression of downstream sex hormones. 4. Chemical castration: Testosterone (males) or estrogen (females) falls to castrate/menopausal levels, achieving the therapeutic goal in hormone-dependent conditions.
Legal Status
FDA-approved prescription medication (Trelstar). Available by prescription only. Not a controlled substance.
Primary Sources
- Triptorelin 6-month depot for the treatment of advanced prostate cancer. European Urology, 2009.
- GnRH agonists in the treatment of endometriosis: a Cochrane review. Cochrane Database of Systematic Reviews, 2010.
- Triptorelin for central precocious puberty: efficacy and safety. Journal of Clinical Endocrinology & Metabolism, 2004.