Gonadorelin is the synthetic form of gonadotropin releasing hormone, the hypothalamic decapeptide that governs luteinising hormone and follicle stimulating hormone release from the anterior pituitary. Its sequence is identical to the native hormone, with a pyroglutamate at the N-terminus and a glycinamide at the C-terminus. It is the reference agonist against which every GnRH analogue, agonist and antagonist alike, is characterised.
Key facts
| Type | Native sequence hypothalamic decapeptide, GnRH agonist |
| Amino acid count | 10 |
| Sequence | pGlu-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-Gly-NH2 |
| Molecular formula | C55H75N17O13 |
| Molecular weight | 1182.3 g/mol |
| CAS number | 33515-09-2 |
| Receptor | GnRH receptor, a class A G protein-coupled receptor on pituitary gonadotrophs |
| Synonyms | GnRH, GnRH-I, LHRH, luteinising hormone releasing hormone |
Structure and chemistry
Both termini are blocked. The N-terminal glutamine cyclises to pyroglutamate, removing the free amine, and the C-terminus is amidated after removal of the terminal glycine of the precursor. Those modifications are structural and not incidental: the pyroglutamate and the glycinamide both make direct receptor contacts, and analogues that open either terminus lose most of their affinity.
The peptide adopts a beta-turn around glycine at position 6 that brings the two ends into proximity, and it is that folded conformation the receptor recognises. Glycine 6 is also the primary cleavage site for the endopeptidase that clears the hormone, which is why almost every long-acting analogue substitutes a bulky D-amino acid at that position. Leuprorelin uses D-leucine, goserelin D-serine with a tert-butyl ether, and nafarelin D-2-naphthylalanine, all with the same aim of blocking cleavage and stabilising the turn.
Tryptophan at position 3 and tyrosine at position 5 make the molecule light sensitive and give it a useful ultraviolet chromophore. Solutions are protected from light and quantified by absorbance at 280 nanometres. Native sequence gonadorelin has a serum half-life of two to four minutes, an order of magnitude shorter than any of the substituted analogues, and that short exposure is precisely what makes it the right tool for studying pulsatile signalling.
Mechanism of action
The GnRH receptor couples through Gq to phospholipase C beta. Receptor activation raises inositol trisphosphate and diacylglycerol, releases calcium from intracellular stores and activates protein kinase C, driving exocytosis of stored gonadotropin and transcription of the LHbeta and FSHbeta subunit genes. The receptor is unusual in lacking a C-terminal cytoplasmic tail, which slows beta-arrestin recruitment and gives it a distinctive desensitisation profile.
Frequency, and not concentration alone, determines the output. Pulsatile exposure at roughly one pulse per hour favours luteinising hormone; slower pulses favour follicle stimulating hormone; continuous exposure downregulates the receptor and suppresses both, which is the basis on which long-acting agonists are used to shut the axis down. Gonadorelin is the tool used to reproduce those regimes in perifusion culture because its rapid clearance lets a pulse be delivered and then withdrawn, something a substituted analogue cannot do.
Research applications
- Pituitary perifusion culture delivering defined GnRH pulse frequencies and measuring LH and FSH output.
- Receptor desensitisation time courses comparing pulsatile against continuous exposure in gonadotroph lines.
- Calcium flux and inositol phosphate accumulation assays used to quantify Gq coupling efficiency.
- Comparative pharmacology screens positioning agonists and antagonists against the native decapeptide.
- Enzymatic stability studies mapping cleavage at the Gly6 site and the effect of D-amino acid substitution.
- Gonadotropin subunit gene transcription assays measuring LHbeta and FSHbeta promoter response to pulse pattern.
Compounds acting on this axis sit in NuVion’s Reproductive Signalling category.
Handling in the laboratory
Gonadorelin is supplied lyophilised, usually as the acetate salt, and is reconstituted with bacteriostatic water added slowly down the wall of the vial and swirled. Peptide content on the certificate is what matters for molar calculations, since acetate and residual water can account for a noticeable fraction of the vial mass. The reconstitution calculator converts vial content and diluent volume into a stock concentration.
The tryptophan at position 3 is the stability limit. It photo-oxidises under ultraviolet and strong visible light and oxidises chemically in the presence of peroxides or trace metals, giving degradation products that separate readily on reversed phase. Vials are held in the dark, working solutions are prepared in amber tubes or foil-wrapped, and stock is aliquoted at first reconstitution. Adsorption to glass is measurable at low micromolar concentration, so dilute standards are prepared in low-binding plastic with a carrier protein where the assay permits.
Testing and supply from NuVion
NuVion supplies a tested range across reproductive signalling, including HCG, Kisspeptin and PT-141. That range is manufactured at a GMP-audited facility and independently tested by Janoshik Analytical, with purity determined by RP-HPLC and identity confirmed by mass spectrometry, and the certificates are published in the Certificate of Analysis library. Gonadorelin is not part of the current catalogue and this page is a reference profile.
Related compounds
Upstream of the decapeptide, kisspeptin is the principal driver of GnRH neuron firing and sets the pulse generator. Downstream, HCG acts at the luteinising hormone receptor on gonadal tissue and bypasses the pituitary step. PT-141 covers melanocortin signalling in the same category, and oxytocin the posterior pituitary nonapeptides.
Frequently asked questions
Is gonadorelin the same as GnRH?
Yes. Gonadorelin is the international nonproprietary name for the synthetic decapeptide with the native human gonadotropin releasing hormone sequence. GnRH, GnRH-I and LHRH all refer to the same molecule, with LHRH being the older name from before follicle stimulating hormone release was attributed to it.
Why is gonadorelin cleared so much faster than leuprorelin or nafarelin?
Because it keeps glycine at position 6, which is the site an endopeptidase cleaves. Substituted analogues replace that glycine with a bulky D-amino acid, blocking cleavage and extending the serum half-life from minutes to hours. The trade is that continuous exposure downregulates the receptor, so the long-acting analogues suppress the axis where pulsed native peptide stimulates it.
Why does pulse frequency matter more than concentration?
The GnRH receptor and its downstream transcription programmes respond to the pattern of exposure. Roughly hourly pulses favour luteinising hormone output, slower pulses favour follicle stimulating hormone, and unbroken exposure downregulates the receptor and suppresses both. Perifusion systems exist to reproduce those patterns because a static culture cannot.
Is gonadorelin listed in the Australian Register of Therapeutic Goods?
Material supplied as a laboratory chemical for in vitro research is not an ARTG-listed product and has not been assessed by the Therapeutic Goods Administration for quality, safety or efficacy. Compounds of this class are supplied in Australia for laboratory use only.
Research use only. The compound described on this page is discussed as a laboratory chemical used in in vitro research. It is not included in the Australian Register of Therapeutic Goods and has not been assessed by the Therapeutic Goods Administration for quality, safety or efficacy. It is not for human or veterinary use, and nothing on this page is a representation about therapeutic use.
