Triptorelin

Mechanism

Triptorelin is a synthetic decapeptide analogue of natural GnRH (LHRH), with modifications at positions 6 (D-tryptophan) and 10 (ethylamide) that increase its receptor binding affinity and resistance to enzymatic degradation. Initially, continuous administration stimulates the pituitary GnRH receptors, causing a transient surge in LH and FSH release (the 'flare' phase, lasting 1–2 weeks). With continued stimulation, the pituitary GnRH receptors become desensitised (downregulated), leading to suppressed LH and FSH secretion. This results in decreased gonadal steroidogenesis — testosterone falls to castration levels in men, and oestradiol falls to postmenopausal levels in women. Recovery of the pituitary-gonadal axis occurs weeks to months after discontinuation.

Evidence base

Prostate Cancer

Triptorelin achieves and maintains castration-level testosterone suppression in >95% of patients with advanced prostate cancer, with efficacy equivalent to orchiectomy and other GnRH agonists. Long-term studies show sustained PSA control and progression-free survival comparable to leuprolide and goserelin (Tannock et al., NEJM, 2004; Sharma & Sharma, StatPearls, 2024).

Central Precocious Puberty

Triptorelin is the standard of care for central precocious puberty. It effectively suppresses the hypothalamic-pituitary-gonadal axis, halting premature puberty progression and improving predicted adult height. The GnRH stimulation test is used to confirm diagnosis and monitor suppression (Carel et al., NEJM, 2008).

Assisted Reproduction

In long agonist protocols, triptorelin effectively prevents premature LH surges during controlled ovarian stimulation. As an agonist trigger in antagonist cycles, it triggers final oocyte maturation while significantly reducing OHSS risk compared with hCG (Humaidan et al., Hum Reprod Update, 2012).

Endometriosis and Uterine Fibroids

Triptorelin provides symptomatic relief and reduces endometriotic lesion size and fibroid volume through oestrogen suppression, though long-term use is limited by bone density loss and menopausal side effects.

Protocols

Prostate Cancer (Depot)

• 3.75 mg IM or SC depot every 28 days, or
• 11.25 mg depot every 12 weeks, or
• 22.5 mg depot every 24 weeks (where available).

Central Precocious Puberty

• 50 µg/kg SC depot every 28 days, titrated to hormonal response.

IVF Long Protocol

• 0.1 mg SC daily from luteal phase Day 21, through stimulation to hCG trigger.

Agonist Trigger (Antagonist Protocol)

• 0.2 mg SC single dose to trigger final oocyte maturation.

All dosing reflects the licensed UK SmPC. This is a POM; administration occurs under specialist supervision. This profile is for research and educational purposes only.

UK legal status

Triptorelin is a prescription-only medicine (POM) in the UK under the Human Medicines Regulations 2012. It is licensed for prostate cancer, endometriosis, uterine fibroids, central precocious puberty, and assisted reproduction. The licensed products (Decapeptyl, Gonapeptyl) hold UK marketing authorisations regulated by the MHRA. Supply without a valid prescription is unlawful. It is not classified as a controlled substance under the Misuse of Drugs Act 1971.

Vendor notes

As a licensed POM, triptorelin is dispensed through hospital and specialist pharmacies upon prescription. It is not available from research peptide vendors. Peptide Data does not list vendors for this compound.