Triptorelin Research, Specifications & Scientific Information

Introduction

Triptorelin differs from the hormone it copies at exactly one position. Glycine at residue 6 is replaced by D-tryptophan — and for years the compound was known by nothing more elaborate than that fact, as D-Trp6-LHRH ^[1].

That single substitution produces a molecule used for the opposite purpose to the natural hormone. Gonadorelin, given in pulses, switches the reproductive axis on. Triptorelin, given as a depot that releases continuously for one, three or six months, switches it off. Neither is a receptor blocker; both are agonists at the same receptor. What separates them is how long the receptor stays occupied, and the reason that matters was established in 1978, when continuous and intermittent delivery of the hormone were compared directly and found to produce opposite pituitary responses ^[7].

Depot products containing triptorelin are approved medicines in the United States and elsewhere. This page describes the compound and its clinical research record, and is explicit about what those approvals cover.

What Is Triptorelin?

Triptorelin is a synthetic decapeptide: pGlu-His-Trp-Ser-Tyr-D-Trp-Leu-Arg-Pro-Gly-NH2. Set beside the natural hormone, nine residues and both terminal modifications are unchanged; position 6 is D-tryptophan where the hormone has glycine.

Position 6 is not an arbitrary place to modify. It sits at the centre of the sequence, at the principal site where enzymes cleave the native hormone, and a D-amino acid there is not a substrate for those enzymes. The substitution therefore does two things at once: it extends the molecule's survival, and it increases affinity for the receptor. Nearly every clinically used agonist in this family carries a D residue at position 6 for the same reason.

PubChem holds the peptide under compound identifier 25074470, with CAS registry number 57773-63-4 and FDA/NCATS UNII code 9081Y98W2V. The acetate and pamoate salts have their own codes; the pamoate is the salt used in the long-acting depot products.

Finished products containing it are approved in the United States — a pamoate depot in the palliative treatment of advanced prostate cancer, and a separate depot formulation in central precocious puberty. Other jurisdictions license further indications, including endometriosis and uterine fibroids, under their own product licences. Every one of those approvals attaches to a particular finished product, presentation and indication. None extends to research-grade material supplied for laboratory use.

Triptorelin Specifications

Triptorelin differs from the native hormone at exactly one position: glycine at position 6 is replaced by D-tryptophan, which is why the compound was known for years simply as D-Trp6-LHRH. Position 6 sits at the centre of the enzymatic cleavage site, and substituting a D residue there blocks the principal degradation route while increasing receptor affinity. The remaining nine residues, the N-terminal pyroglutamate and the C-terminal amide are all as in gonadorelin. PubChem carries the peptide under compound identifier 25074470 with CAS registry number 57773-63-4 and the FDA/NCATS UNII code 9081Y98W2V; the acetate and pamoate salts carry their own codes, 43OFW291R9 and 08AN7WA2G0, and the pamoate is the salt used in the long-acting depot products. Mass spectrometry cannot distinguish D-tryptophan from L-tryptophan, so an intact-mass result is consistent with this molecule and equally consistent with the all-L peptide, which is a different pharmacological entity.

Values that a public register does not carry are shown as not publicly characterised rather than estimated. Identifiers are reference values; the certificate of analysis supplied with a laboratory order is the record for a given lot.

How Does Triptorelin Work?

It is a full agonist at the gonadotropin-releasing hormone receptor, and it is used to suppress the axis. Those two statements only appear to conflict.

The receptor is a Gq/11-coupled class A G protein-coupled receptor on pituitary gonadotrope cells. In normal physiology it receives pulses of hormone every sixty to ninety minutes and responds to each with a burst of luteinising hormone and follicle-stimulating hormone release. Its behaviour under sustained rather than pulsed stimulation is different in kind: receptor numbers fall, coupling is lost, and gonadotropin output collapses. The 1978 experiment that established this compared the two delivery patterns side by side and found them to produce opposite results with the same molecule ^[7].

A depot formulation releasing peptide continuously for months creates precisely the suppressive condition. The sequence of events in a treated patient is therefore:

1. Flare. In the first days, agonist action raises luteinising hormone, follicle-stimulating hormone and sex steroid concentrations. This is intrinsic to the class, is expected, and is managed clinically.
2. Desensitisation. Sustained occupancy downregulates the receptor.
3. Suppression. Gonadotropin output falls, and sex steroid production falls with it — to castrate concentrations in adults, to prepubertal concentrations in children.

The therapeutic effect is stage three. Stage one is the price of reaching it with an agonist, and it is the main reason receptor antagonists were later developed as an alternative: an antagonist produces no flare because it never stimulates.

Triptorelin Mechanism of Action

The mechanism above is classical endocrine pharmacology established across the 1970s and 1980s, and no in vitro receptor characterisation performed specifically on triptorelin was located for this page. The two load-bearing results are the pattern-dependence of the receptor's response ^[7] and the clinical demonstration that a long-acting form of this molecule achieves suppression comparable to surgical castration ^[1].

Nothing here is uncertain in the way that the mechanism of many compounds in this library is uncertain. The receptor is identified, the ligand is a modified version of its natural agonist, and the therapeutic effect follows from a documented property of the receptor.

What Is Triptorelin Being Researched For?

• Advanced prostate cancer — androgen deprivation, established against surgical castration in a randomised comparison ^[1] and characterised since for the depth and durability of testosterone suppression achieved with sustained-release formulations ^[2].
• Central precocious puberty — suppression of a prematurely activated axis in children, with phase 3 trials of three-month and six-month depot formulations ^{[3, 4]} and review-level assessment of the compound and its class in paediatric use ^{[5, 6]}.
• Gynaecological indications — endometriosis and uterine fibroids, under licences held outside the United States.
• Formulation intervals — much of the recent registered research asks how long a single administration can maintain suppression rather than whether suppression occurs.

Each of those is research on an approved medicine, conducted under protocol in defined patient populations. None of it is research into, or evidence about, research-grade material supplied for laboratory use.

Human Research on Triptorelin

Human clinical research

Results from pharmaceutical clinical trials describe the investigational material and populations used in those studies and should not be interpreted as establishing the effects of research-grade materials offered for laboratory use.

Advanced prostatic carcinoma against surgical castration, 1985

Design. A randomised controlled study in advanced prostatic carcinoma comparing orchidectomy with long-acting D-Trp-6-LHRH microcapsules ^[1].

Why the comparator matters. Surgical castration was the established treatment. A placebo-controlled trial in that setting would have been indefensible, so the question asked was whether a monthly injection could match an irreversible operation. That framing is the reason this trial mattered, and the reason androgen deprivation is now overwhelmingly pharmacological rather than surgical.

Limitations. A 1985 trial, reported to the conventions of its time, with the endpoints and analytical standards of that period.

Testosterone suppression with sustained-release formulations, 2017

Design and result as reported. An assessment of the efficacy of testosterone suppression achieved with sustained-release triptorelin in advanced prostate cancer ^[2].

What this kind of study measures. Suppression of testosterone below a castrate threshold is a surrogate for the intended pharmacological state, not a clinical outcome in itself. Studies of this kind establish that a formulation delivers and maintains the intended suppression across its stated interval; survival and disease-control questions are answered by different trials.

Central precocious puberty: three-month and six-month formulations

Design. Phase 3, open-label, single-arm trials in Chinese children with central precocious puberty, one of a three-month formulation ^[3] and one of a six-month formulation ^[4].

Why single-arm. In a condition where suppressing the axis is the accepted standard of care, randomising children to no suppression is not acceptable. The design therefore measures whether the formulation achieves and maintains suppression of the pubertal gonadotropin response over the administration interval, against each child's own baseline.

What that design can and cannot establish. It can establish that a longer interval maintains suppression, which is the question a six-month formulation exists to answer. It cannot establish comparative efficacy against another analogue in the class, and it carries no control for the natural course of the condition.

Context. The compound and its class have been reviewed for use in children aged two and over ^[5], and practice across the available analogues in the United States has been surveyed ^[6].

The flare, as a clinical fact

The initial stimulation is not an adverse surprise but a predicted consequence of agonism at this receptor ^[7]. It is the reason antagonists at the same receptor occupy a distinct clinical niche, and it is the single most important thing to understand about how this class of compound behaves in the first week of exposure.

Current Research Status

Status as of September 22, 2026. This block is rendered from maintained fields, not from prose, so it cannot go stale in one place and stay current in another.

Triptorelin vs Related Compounds

Against Gonadorelin

Gonadorelin is the natural hormone, cleared within minutes and stimulating the axis when delivered in pulses. Triptorelin differs by one residue, resists cleavage, and is formulated for months of continuous release — so it suppresses. The comparison is the clearest available demonstration that pharmacological effect can be determined by exposure pattern rather than by structure ^[7].

Against other agonists in the class

Leuprolide, goserelin and buserelin share the strategy of a D-amino acid at position 6 and a sustained-release formulation. They are distinct molecules with distinct products and licences, and practice surveys describe them side by side rather than as interchangeable ^[6].

Against GnRH antagonists

Antagonists block the receptor from the first administration and produce no flare. The trade-off is pharmacological rather than about potency: an agonist reaches suppression through a period of stimulation, an antagonist reaches it immediately.

Against the kisspeptins

Kisspeptin-54 and kisspeptin-10 act on the hypothalamic neurons upstream of this receptor rather than on the pituitary. They stimulate through the body's own GnRH pulse generator, which is a different level of intervention and produces a differently shaped hormone response.

No comparison of effect between these compounds is made on this page.

Chemical & Molecular Characteristics

Triptorelin is a ten-residue peptide of molecular formula C64H82N18O13 and average mass 1311.4 g/mol, under PubChem compound identifier 25074470 and CAS registry number 57773-63-4.

Mass cannot confirm the defining feature. D-tryptophan and L-tryptophan are identical in mass. An intact-mass measurement consistent with 1311.4 daltons is equally consistent with the all-L peptide, which is not this compound and does not have its pharmacology. Confirming the D configuration requires chiral analysis. This is the most consequential analytical point about the molecule, and the same point applies to every D-substituted analogue in this class.

Two tryptophans, one of each hand. Position 3 is L-tryptophan, inherited from the natural sequence, and position 6 is the D form. Both indoles are oxidation- and light-sensitive, and their oxidation products are close in mass and frequently poorly resolved from the parent peak. A peptide with two such residues has twice the exposure to that failure mode.

Both termini are modified, as in the parent hormone. The N-terminal pyroglutamate and the C-terminal amide are features of the natural molecule rather than stabilising additions, and both are required for activity. A free C-terminal acid differs by one dalton and is not an agonist.

The salt is part of the product. The pamoate salt used in depot products is what gives them their release characteristics; the acetate is the common reagent form. The two carry different UNII codes — 08AN7WA2G0 and 43OFW291R9 — and materially different masses per unit of peptide. A purity or mass figure that does not state the counter-ion and water content is incomplete.

Depot behaviour is a property of the formulation, not of the peptide. The microsphere and implant systems that release this molecule over one, three or six months are engineered products in their own right. Nothing about a peptide powder reproduces them, and the trial results described above were all generated with those formulations.

Frequently Asked Questions

Scientific References

1. Parmar H, Phillips RH, Lightman SL, et al.. Randomised controlled study of orchidectomy vs long-acting D-Trp-6-LHRH microcapsules in advanced prostatic carcinoma Lancet (London, England); 1985. PMID 2866289 doi:10.1016/s0140-6736(85)90739-1
2. Breul J, Lundström E, Purcea D, et al.. Efficacy of Testosterone Suppression with Sustained-Release Triptorelin in Advanced Prostate Cancer Advances in therapy; 2017. PMID 28028737 doi:10.1007/s12325-016-0466-7
3. Luo X, Zhang C, Yang Y, et al.. Efficacy and Safety of Triptorelin 3-Month Formulation in Chinese Children with Central Precocious Puberty: A Phase 3, Open-Label, Single-Arm Study Advances in therapy; 2023. PMID 37584898 doi:10.1007/s12325-023-02617-8
4. Yu X, Cheng X, Wei H, et al.. A Phase 3, Open-Label, Single-Arm Trial of the Efficacy and Safety of Triptorelin 6-Month Formulation in Chinese Children with Central Precocious Puberty Advances in therapy; 2024. PMID 39412628 doi:10.1007/s12325-024-02991-x
5. Bertelloni S, Mucaria C, Baroncelli GI, et al.. Triptorelin depot for the treatment of children 2 years and older with central precocious puberty Expert review of clinical pharmacology; 2018. PMID 29957076 doi:10.1080/17512433.2018.1494569
6. Popovic J, Geffner ME, Rogol AD, et al.. Gonadotropin-releasing hormone analog therapies for children with central precocious puberty in the United States Frontiers in pediatrics; 2022. PMID 36268040 doi:10.3389/fped.2022.968485
7. Belchetz PE, Plant TM, Nakai Y, et al.. Hypophysial responses to continuous and intermittent delivery of hypopthalamic gonadotropin-releasing hormone Science (New York, N.Y.); 1978. PMID 100883 doi:10.1126/science.100883

Every identifier above is resolved against PubMed, Crossref or ClinicalTrials.gov at build time, and the title returned by the register is compared with the title stored here. A page does not publish if a reference fails to resolve.

Research-Use Information

For in vitro research use only. This material is a laboratory reagent. It is not a drug, food, dietary supplement, or cosmetic and is not for human or veterinary use, including ingestion, injection, or any other administration. No information on this page describes or implies any effect in humans or animals. Sold only to researchers under our Terms of Sale.