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Professor Peptides
FDA approved

Triptorelin

Also known as Triptorelin · Trelstar · triptorelin pamoate · GnRH agonist

FDA-approved GnRH agonist (Trelstar) producing sustained gonadal suppression after initial flare

Last reviewed · Educational reference — not medical advice.

Formula
C64H82N18O13
Molecular weight
1,311.4 g/mol
Half-life
Not characterised in published human pharmacokinetic studies
Route
Intramuscular or subcutaneous depot injection, clinician-administered
CAS
57773-63-4
PubChem
25074470 (opens in new tab)
Status
FDA-approved drug — Trelstar, NDA020715
Mechanism
GnRH receptor agonist. Continuous (non-pulsatile) receptor stimulation first causes a surge in LH, FSH and sex steroids, then downregulates and desensitises pituitary GnRH receptors, producing sustained suppression of gonadotropin and sex steroid production.
01

Overview

Triptorelin is a synthetic decapeptide agonist of gonadotropin-releasing hormone. It is FDA-approved and marketed as Trelstar under NDA020715, with additional applications NDA021288 and NDA022437, verified against the openFDA drug label database.

Its pharmacology is counterintuitive and frequently misunderstood on vendor sites. GnRH is normally released in

pulses , and the pituitary responds to that pulsatility. A long-acting agonist provides continuous rather than pulsatile stimulation, which initially causes a surge in LH, FSH and therefore testosterone — the so-called flare — and then, with sustained exposure, downregulates and desensitises pituitary GnRH receptors, producing profound suppression of gonadotropins and sex steroids.

The net clinical effect is therefore chemical castration, which is why it is used in advanced prostate cancer, endometriosis, uterine fibroids and central precocious puberty. This matters because triptorelin is sometimes listed alongside gonadorelin and hCG on peptide sites as if it were similarly a stimulator of the reproductive axis. It is the opposite: gonadorelin given in pulses stimulates the axis, whereas triptorelin given continuously shuts it down.

The initial flare is itself clinically significant — it can transiently worsen hormone-sensitive disease, which is why anti-androgen cover is standard practice in prostate cancer.

Research areasGnRH receptor pharmacologyAndrogen deprivation therapyEndometriosisCentral precocious puberty
02

What the evidence shows

Separated by study type
HumanClinical trials and human studies
Approved for human use with an established clinical evidence base across prostate cancer, endometriosis, uterine fibroids and central precocious puberty.
AnimalRodent and other animal models
Not the primary evidence base; this is an approved human drug.
In vitroCell and tissue studies
GnRH receptor agonism and receptor downregulation are well characterised.
03

Key studies & findings

1 study
  1. 1

    Triptorelin pamoate is FDA-approved and marketed as Trelstar under NDA020715, NDA021288 and NDA022437, verified against the openFDA drug label database.

    openFDA drug label database

04

Benefits & effects

2 documented

  • Sustained suppression of gonadotropins and sex steroids

    HumanVerified

  • Established use in advanced prostate cancer, endometriosis and central precocious puberty

    HumanVerified
05

Side effects & safety

4 reported

Safety notePrescription drug with profound endocrine effects. Sustained administration suppresses sex hormone production, and an initial testosterone surge can transiently worsen hormone-sensitive conditions. Requires clinical supervision.

  • Initial testosterone flare that can transiently worsen hormone-sensitive disease

    unknown

  • Hypogonadal symptoms including hot flushes and loss of libido

    Moderateunknown

  • Bone mineral density loss with sustained use

    unknown

  • Injection site reactions

    Mildunknown
06

Limitations & open questions

Triptorelin suppresses the reproductive axis; it does not support it. Any listing that groups it with gonadorelin or hCG as a testosterone-supporting compound has the pharmacology backwards. Sustained use produces hypogonadism with the expected consequences including bone mineral density loss, and the initial flare can transiently worsen hormone-sensitive conditions. This is a clinician-administered depot drug, not a research compound for self-directed use.

07

Pharmacology

Triptorelin is a synthetic decapeptide (C64H82N18O13, MW 1311.4, CAS 57773-63-4, PubChem CID 25074470), typically formulated as the pamoate salt in long-acting depot preparations. The depot formulation is essential to the mechanism: continuous rather than pulsatile receptor exposure is what produces desensitisation rather than stimulation.

08

Frequently asked questions

Does triptorelin raise or lower testosterone?

Both, in sequence — and the end state is suppression. Continuous stimulation first causes a surge (the flare), then downregulates pituitary GnRH receptors, producing sustained suppression of gonadotropins and testosterone.

How is triptorelin different from gonadorelin?

Dosing pattern determines the outcome. Gonadorelin given in pulses mimics physiological GnRH and stimulates the axis. Triptorelin given continuously as a depot desensitises the receptor and shuts the axis down. They are opposite in net effect despite acting at the same receptor.

Is triptorelin FDA-approved?

Yes — as Trelstar, under NDA020715 with additional applications NDA021288 and NDA022437, verified against the openFDA drug label database.

What is the 'flare' and why does it matter?

The initial surge in LH, FSH and testosterone before receptor desensitisation sets in. In hormone-sensitive prostate cancer it can transiently worsen disease, which is why anti-androgen cover is standard at initiation.