Gonadorelin
Synthetic gonadotropin-releasing hormone with the native ten-residue sequence, freeze-dried in a sealed vial. Every lot is tested in the manufacturer’s own laboratory and ships with a lot certificate.
| Compound | Gonadorelin Native gonadotropin-releasing hormone (GnRH, LHRH) |
|---|---|
| CAS number | 33515-09-2 |
| Molecular formula | C55H75N17O13 |
| Theoretical mass | 1182.3 Da |
| Sequence / structure | pGlu-HWSYGLRPG-NH₂ (10 residues; N-terminal pyroglutamate; C-terminal amide) |
| Label claim | 2 mg/vial |
| Form | Lyophilized (freeze-dried) powder or cake in a sealed glass vial with a rubber stopper and aluminium crimp cap |
| Storage, sealed | −20 °C, desiccated, dark |
| Purity specification | 99.0% or higher by RP-HPLC |
| Format | Lyophilized powder, sealed vial |
Sizes and lots
- 2 mg · 1 vial — $37.25 · lot PL-2609-045, certificate PL-26-00045
- 2 mg · Kit of 10 — $331.15 · lot PL-2609-045, certificate PL-26-00045
Gonadorelin is synthetic gonadotropin-releasing hormone (GnRH, also known as LHRH): the ten-residue peptide through which the hypothalamus controls release of LH and FSH from the pituitary. This vial contains 2 mg as a white freeze-dried powder, with the native sequence, an N-terminal pyroglutamate and a C-terminal amide. Research on GnRH covers its pituitary receptor and how that receptor signals, and a classic primate study showing that the pattern of exposure decides whether the pituitary responds.
The native sequence, unmodified
The certificate gives the sequence as pGlu-HWSYGLRPG-NH2: ten residues, starting with pyroglutamic acid and ending in glycinamide, formula C55H75N17O13, theoretical mass 1182.3 Da. That is the hormone itself, made by synthesis rather than by neurons, with no substituted residue and no altered terminus. GnRH agonists such as triptorelin, described in the triptorelin guide, are modified versions of this sequence. The structure was first proposed in 1971 by Matsuo and colleagues, working from the porcine hormone1.
With the mass stated, molar amounts are simple arithmetic: 2 mg of a 1182.3 Da peptide is about 1.7 µmol. The true figure is slightly lower, because the powder also holds the residual water the certificate reports. The same peptide is sold in solution as a gonadorelin nasal spray.
What the research covers
The receptor and its signalling
GnRH is an old and widely varied signal. Millar and colleagues counted 23 structural variants of GnRH across protochordates and vertebrates, and in many vertebrates three GnRH forms paired with three receptors, each with its own distribution and functions2. In humans, hypothalamic GnRH controls gonadotropin secretion through the pituitary type I GnRH receptor, which acts mainly by activating the G protein Gq2. Detailed studies have identified residues in both the hormone and the receptor that are involved in binding, in activating the receptor and in passing the signal into the cell2. Coupling to other G proteins, and possibly signalling that does not need G proteins at all, has also been described, and the review suggested that variations in ligand structure may steer which intracellular pathway is selected2. A second form, GnRH II, is conserved in all higher vertebrates including humans and is found outside the hypothalamus2.
The same review placed this work in a clinical context. GnRH and its analogues are used extensively for hormone-dependent diseases and in assisted reproduction, and Millar's group described their potential as contraceptives in men and women2.
Pulsed and continuous exposure
The best known experiment on GnRH is about timing rather than amount. Belchetz and colleagues worked with rhesus monkeys whose hypothalamic lesions had abolished gonadotropin release by the pituitary3. A constant infusion of synthetic GnRH failed to restore sustained gonadotropin secretion. Intermittent delivery, timed to the physiological rhythm of gonadotropin release in these monkeys, did restore it, and the authors attributed the difference to the pattern of delivery rather than the amount of hormone reaching the pituitary3. When monkeys whose secretion had been restored this way were switched to continuous GnRH, the processes responsible for gonadotropin release could become desensitized, or down-regulated3.
For GnRH, then, the pattern of exposure is part of the experiment: the same synthetic hormone restored pituitary output in one arrangement and failed to in the other3.
What is not established
The evidence cited on this page is receptor biology, the original sequence work and one primate study from 1978. The older human literature, including gonadorelin's history as a diagnostic agent, and its comparison with hCG, which acts on a different receptor in a different organ, are set out in the gonadorelin guide.
Frequently asked questions
Is gonadorelin the same as natural GnRH?
Yes. It has the native ten-residue sequence, with pyroglutamate at the N-terminus and an amide at the C-terminus, and a theoretical mass of 1182.3 Da. The LC-MS identity result on the certificate is the figure to compare with that mass.
How does the 2 mg vial differ from the nasal spray?
The vial holds 2 mg of dry peptide that is stored at −20 °C and dissolved only when a study needs it. The spray holds 10 mg already in bacteriostatic water with benzyl alcohol, kept at 2 to 8 °C and never frozen. The peptide is the same in both.
How should the vial be stored?
Sealed at −20 °C, dry and dark, as the certificate specifies. Let the vial reach room temperature before opening so moisture does not condense on the powder. A solution goes to 2 to 8 °C, away from light, for a period your laboratory has validated.
Why does the pattern of exposure matter in GnRH research?
Because the pituitary responds to the rhythm of the signal as well as its size. In a 1978 primate study, intermittent GnRH restored gonadotropin secretion that continuous exposure could not, and switching to continuous delivery could desensitize the response.
References
- Matsuo H, Baba Y, Nair RM, et al. Structure of the porcine LH- and FSH-releasing hormone. I. The proposed amino acid sequence. Biochem Biophys Res Commun. 1971;43(6):1334-9. DOI · PubMed
- Millar RP, Lu ZL, Pawson AJ, et al. Gonadotropin-releasing hormone receptors. Endocr Rev. 2004;25(2):235-75. DOI · PubMed
- Belchetz PE, Plant TM, Nakai Y, et al. Hypophysial responses to continuous and intermittent delivery of hypopthalamic gonadotropin-releasing hormone. Science. 1978;202(4368):631-3. DOI · PubMed
For laboratory research use only. Not for human or veterinary consumption. Products have not been evaluated by the U.S. Food and Drug Administration and are not intended to diagnose, treat, cure or prevent any disease.