Gonadorelin: synthetic fertility hormone (CHEMBL436874)
Lab-made copy of the brain's master reproductive hormone; tells the pituitary gland to release the hormones that drive fertility, used as a fertility treatment and diagnostic test.
A researcher, an agent, or an algorithm wrote down the sequence and picked a target to hit.
An AI model like OpenFold3 or AlphaFold built a 3D structure and scored how well it fits the binding site.
A second contributor repeated the computation on their own hardware and the scores matched.
A chemistry service or a researcher ordered the sequence, it was manufactured, and mass spectrometry confirmed the right molecule was produced.
A binding or activity measurement confirmed that it actually does what the computer predicted — or didn't.
What this is
This card holds the bare 10-amino-acid backbone of gonadotropin-releasing hormone (GnRH) — the master reproductive hormone made by the hypothalamus. The synthetic version of GnRH used in medicine is called gonadorelin (formerly sold as Factrel for diagnostic pituitary testing and Lutrepulse for pulsatile fertility therapy). The stored sequence EHWSYGLRPG is the unmodified residue chain; the active hormone is actually pyroGlu-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-Gly-NH2, with a cyclized pyroglutamate at the N-terminus and a C-terminal amide — neither of which is encoded by the raw one-letter sequence shown here. Both modifications are essential for receptor binding and protect the peptide from aminopeptidase and carboxypeptidase degradation. The ChEMBL entry CHEMBL436874 that this card is keyed to reports a GnRH receptor (GnRHR) binding affinity of approximately 0.8 nM, consistent with native GnRH potency.
History
GnRH was isolated and sequenced in the early 1970s by the laboratories of Andrew Schally and Roger Guillemin — work that contributed to their sharing the 1977 Nobel Prize in Physiology or Medicine. The 10-residue sequence shown on this card is identical to the endogenous human hormone. In the US, synthetic gonadorelin was marketed as Factrel (Ayerst/Wyeth) for pituitary function testing and as Lutrepulse (Ferring), delivered via programmable subcutaneous pump for primary hypothalamic amenorrhea and related infertility indications. Both products have since been discontinued in the United States, though the FDA approval history remains on the record. Internationally, gonadorelin and close analogs remain widely used in veterinary reproductive medicine — most prominently for ovulation synchronization in cattle — which accounts for a substantial share of its published randomized-trial literature.
What it does
When GnRH is released in pulses (roughly every 60–120 minutes, as the hypothalamus naturally does), it tells the pituitary gland to secrete luteinizing hormone (LH) and follicle-stimulating hormone (FSH). LH and FSH then act on the testes or ovaries to drive testosterone, estrogen, and gamete production. The route of delivery matters as much as the molecule: pulsatile exposure stimulates the axis, while continuous exposure suppresses it through receptor desensitization. That paradox is the basis for an entire class of cancer drugs (GnRH agonists such as leuprolide), which deliver the same receptor signal in a steady-state fashion to shut down sex-hormone production.
Mechanism
GnRH binds the gonadotropin-releasing hormone receptor (GnRHR), a class A G-protein-coupled receptor expressed on pituitary gonadotrophs. Receptor activation signals primarily through Gq/phospholipase C, generating IP3 and DAG, mobilizing intracellular calcium, and triggering LH and FSH synthesis and secretion. Pulse frequency biases the LH-versus-FSH output. The GnRHR is also expressed at lower levels outside the pituitary, where multiple structural classes of small-molecule ligands — both peptide and non-peptide — engage overlapping but non-identical pockets on the receptor, a binding-site architecture mapped in detail by Betz and colleagues (J Med Chem, 2006).
Evidence
- Human: Decades of well-characterized use in diagnostic pituitary-function testing and approved pulsatile pump therapy for hypothalamic amenorrhea. Receptor pharmacology and HPG-axis physiology are among the most thoroughly studied in endocrinology.
- Animal: Extensive randomized-controlled literature, dominated by veterinary reproductive applications (cattle, llamas, horses). The PMID record indexed under "gonadorelin" is dense with bovine ovulation-synchronization and fertility protocols.
- In vitro: The ChEMBL entry CHEMBL436874 reports sub-nanomolar GnRHR binding. Receptor signaling has been dissected across recombinant cell systems and primary pituitary gonadotroph preparations.
Known effects
- Pituitary LH/FSH release — well-characterized; the basis for diagnostic stimulation testing
- Restoration of ovulation in hypothalamic amenorrhea — historical FDA-approved indication (Lutrepulse)
- Receptor desensitization on continuous exposure — the mechanism leveraged by leuprolide-class GnRH agonists to suppress the HPG axis in prostate cancer and endometriosis
- Veterinary ovulation induction and estrus synchronization — extensively documented in bovine reproductive medicine
Safety signals
Reported adverse effects from the human use literature include injection-site reactions, headache, nausea, and flushing. Hypersensitivity and anaphylactoid reactions have been documented with repeated diagnostic dosing. The pharmacology is unusual in that the same molecule can either stimulate or suppress the reproductive axis depending on the temporal pattern of exposure — a property that has clinical consequences when the delivery schedule does not match the intended effect.
Regulatory status
- US: Both historical FDA-approved products — Factrel (diagnostic) and Lutrepulse (pulsatile pump therapy) — have been discontinued. There is currently no FDA-approved commercial gonadorelin product in the United States. In 2024, the FDA flagged gonadorelin for safety review in the 503A compounding context.
- International: Veterinary use remains extensive worldwide. Human prescribing varies by jurisdiction; some countries retain approved human-use products for diagnostic or fertility indications.
- WADA: Prohibited at all times (in and out of competition) under category S2 — peptide hormones and their releasing factors — regardless of therapeutic intent.
Myths and misconceptions
- "Gonadorelin is a currently FDA-approved drug." — It was historically (as Factrel and Lutrepulse). Both products are discontinued in the US. The approval history remains on record but no commercial product is marketed.
- "Gonadorelin and hCG do the same thing." — They act at different levels of the axis. hCG mimics LH and acts directly on Leydig cells; gonadorelin acts upstream on the pituitary, preserving the whole HPG cascade.
- "Continuous dosing produces a stronger effect than pulsatile dosing." — The opposite. Continuous GnRHR exposure desensitizes the receptor and suppresses gonadotropins — the same mechanism leuprolide uses therapeutically. Gonadorelin only stimulates when delivered in pulses.
Related peptides
- Kisspeptin — the upstream hypothalamic signal that drives endogenous GnRH neuron firing
- Leuprolide — a long-acting GnRH agonist that produces sustained receptor occupancy, paradoxically suppressing the HPG axis (used in prostate cancer, endometriosis, central precocious puberty)
- hCG (human chorionic gonadotropin) — acts downstream at the Leydig-cell LH receptor, bypassing the pituitary
Open questions
- The non-identical, partially overlapping binding pockets used by different chemical classes of GnRHR ligands (Betz et al., J Med Chem, 2006) leave room for further selectivity tuning between agonist and antagonist scaffolds.
- The contribution of extra-pituitary GnRHR expression to whole-organism physiology remains less characterized than the pituitary axis.
- Long-term safety datasets for chronic pulsatile gonadorelin exposure beyond the months-long Lutrepulse pregnancy protocols have not been formally established.
Research directions for this peptide, selected from the current sources — hypotheses you can explore and model. None of it is proven yet; tap any one to see the full thinking.
Does the GnRH receptor's own reset speed determine the ratio of LH to FSH that the pituitary makes?
If receptor reset speed is the key control dial, doctors could program fertility pumps more precisely based on the receptor's known properties rather than trial and error, potentially improving success rates for people with hypothalamic infertility.
Does the raw, unmodified version of gonadorelin trigger a different internal cell response than the chemically finished hormone?
If the unmodified version activates a distinct cellular pathway, it could become the starting point for fertility drugs that stimulate reproduction without triggering the paradoxical shutdown that current hormone therapies cause when given continuously.
▸full evidence table1 metrics
| metric | value | tool |
|---|---|---|
| IC50 | 0.8 nM | GPCRDB/ChEMBL |
▸3-letter notation
▸recipeboltz-2 2.2.1
| parameter | value |
|---|---|
| model | boltz-2 2.2.1 |
| weights | — |
| hardware | vast_v100_32gb |
| mlx version | — |
| python | — |
| random seed | 1 |
| msa strategy | colabfold_local |
| runtime | — |
| predicted by | — |
| predicted at | 2026-05-22 |
▸citationbibtex
@peptide{pep10375,
sequence = {EHWSYGLRPG},
target = {gnrhr},
author = {peptidemodel},
year = {2026},
status = {bioassayed}
}