Sex-hormone control fragment (LHRH 4-10)
A small piece of the body's natural hormone-release signal that acts on the pituitary gland; used only as a lab research tool to study how reproductive hormones are controlled.
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
LHRH (4-10) is the C-terminal heptapeptide fragment of gonadotropin-releasing hormone (GnRH), the hypothalamic hormone that controls sex-hormone production. The full GnRH decapeptide — pyroGlu-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-Gly-NH₂ — is released from the hypothalamus in pulses to stimulate pituitary production of LH and FSH, which in turn drive testosterone and estrogen synthesis in the gonads (Flanagan and colleagues, 2017). LHRH (4-10) contains only the C-terminal seven residues (Ser-Tyr-Gly-Leu-Arg-Pro-Gly) — the portion that begins at position 4 of the parent decapeptide and runs to the end. It lacks the first three N-terminal residues (pyroGlu, His, Trp) that are required to activate the GnRH receptor. The stored sequence SYGLRPG is the standard single-letter representation; in characterized preparations the C-terminus carries an amide group (–NH₂), which is present in native GnRH but is not visible in the stored one-letter sequence.
History
GnRH was isolated and sequenced in the early 1970s by Andrew Schally's and Roger Guillemin's laboratories, work recognized with the 1977 Nobel Prize in Physiology or Medicine. Once the full sequence was known, fragment analysis became a major tool for mapping which parts of the decapeptide drive receptor binding versus receptor activation. By the mid-1980s, structure-activity work had established that the N-terminal triad (pGlu1, His2, Trp3) is primarily responsible for agonist activity, whereas the C-terminal region — including the Arg at position 8 — contributes to high-affinity receptor binding (Flanagan and colleagues, 2017). In this context LHRH (4-10) drew interest as a research reagent: Singh (1989) reported that monoclonal anti-GnRH antibodies generated by immunization against intact GnRH were able to recognize the heptapeptide H-Ser-Tyr-Gly-Leu-Arg-Pro-Gly as an epitope, enabling studies of antibody specificity for the conformational versus sequential features of the parent hormone. This use — as an antigenic fragment for antibody characterization rather than as a standalone bioactive compound — represents the documented research context for LHRH (4-10) in the published literature.
What it does
LHRH (4-10) does not reproduce the gonadotropin-releasing activity of the parent decapeptide. GnRH receptor activation requires the intact N-terminal triad; without pGlu1, His2, and Trp3, a fragment cannot trigger the Gq/11-mediated calcium signaling cascade in pituitary gonadotrophs that drives LH and FSH secretion (Flanagan and colleagues, 2017; Durán-Pastén and colleagues, 2013). The fragment retains the Arg8 residue (position 5 in the fragment's own sequence) that contributes to C-terminal receptor-binding affinity, and the terminal Pro-Gly-NH₂ motif conserved across GnRH variants in vertebrates — but affinity for GnRHR without the N-terminal activation segment has not been demonstrated to produce a functional response. The primary documented use of LHRH (4-10) is as a synthetic antigenic fragment in antibody epitope mapping studies of the GnRH axis (Singh, 1989).
Evidence
- Human: No clinical trials evaluating LHRH (4-10) as an isolated therapeutic or investigational agent were identified. The broader GnRH therapeutic space — full-length analogs such as leuprolide and goserelin — has been extensively studied in human trials; those findings pertain to intact receptor agonists or antagonists and do not transfer to this fragment.
- Animal: No animal-model studies examining biological activity specific to LHRH (4-10) were identified in the available sources.
- In vitro: LHRH (4-10) has been used in competitive binding and ELISA assays to characterize the epitope specificity of anti-GnRH monoclonal antibodies (Singh, 1989). No independent receptor-activation assay data for this fragment were identified.
Mechanism
Full-length GnRH binds GnRHR on anterior pituitary gonadotrophs and triggers Gq/11-mediated phospholipase C signaling, generating IP3 and DAG, mobilizing intracellular calcium, and stimulating pulsatile LH and FSH release — a pathway well characterized across receptor-binding and calcium-imaging studies (Flanagan and colleagues, 2017; Durán-Pastén and colleagues, 2013). LHRH (4-10) lacks the three N-terminal residues that serve as the receptor's activation switch. Structure-activity data compiled by Flanagan and colleagues (2017) indicate that the amino-terminal residues pGlu1, His2, and Trp3 determine agonist activity, while the carboxy-terminal region (particularly Arg8) is required for high-affinity binding. LHRH (4-10) retains the Arg (position 8 of the parent) and the conserved Pro-Gly-NH₂ tail but lacks the activation signal; this makes it a structural and immunological probe rather than a pharmacological agent. The GnRH receptor lacks the cytoplasmic C-terminal tail present in most GPCRs, which shapes its desensitization kinetics (Finch and colleagues, 2009; Davidson and colleagues, 1994) — a receptor architecture that is broadly relevant to any consideration of truncated ligands but has not been specifically examined with LHRH (4-10).
Open questions
- Whether LHRH (4-10) retains any measurable affinity at GnRHR or at non-canonical GPCRs (such as those reported for the N-terminal fragment GnRH-(1-5)) has not been tested in published assays.
- Whether the C-terminal amide is required for the antibody epitope recognized by anti-GnRH antibodies reactive to LHRH (4-10) has not been resolved (Singh, 1989).
- Whether LHRH (4-10) is produced under physiologically relevant conditions during normal GnRH catabolism — cleavage at the Tyr5-Gly6 bond primarily generates the 1-5 and 6-10 fragments — or whether it arises only from secondary processing of intermediate fragments remains unresolved.
- No structural prediction data for the free heptapeptide in solution are available; the platform Boltz-2 structure (ipTM 0.95, ranking score 0.79) provides a computed reference conformation.
Related peptides
- LHRH (1-5) — the N-terminal pentapeptide of GnRH; contains the activation residues pGlu-His-Trp and has documented orphan-GPCR signaling activity in endometrial cells distinct from the classical GnRHR pathway.
- LHRH (1-6) — the N-terminal hexapeptide; retains the same activation triad as GnRH-(1-5) plus one additional residue; studied in the context of N-terminal fragment signaling.
- Leuprolide — a full 9-residue GnRH analog with D-Leu substitution at position 6 and a C-terminal ethylamide; FDA-approved GnRH agonist that retains the N-terminal activation residues LHRH (4-10) lacks.
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.
Could this fragment block the receptor used by prostate and breast cancer cells without first causing the hormone spike that current drugs produce?
Current GnRH drugs used in prostate cancer cause an initial testosterone surge that can worsen symptoms before improving them. A fragment that skips that step could be safer at the start of treatment and help patients who currently need additional drugs to suppress the flare.
If the fragment's fragile tail were replaced with a slightly altered amino acid that resists breakdown, would it stay intact long enough in the body to be useful?
Most peptide fragments are destroyed too quickly in the bloodstream to be drugs. If a single chemical change can protect this fragment from being degraded, it could become the starting point for a new hormone-suppressing drug for conditions like endometriosis, prostate cancer, or precocious puberty.
Does this peptide bind only the receptor that controls hormone levels, without affecting the related receptor that influences sexual behavior and mood?
Drugs that hit only the intended receptor tend to have fewer side effects. If this fragment targets only the fertility-controlling receptor, it could potentially be used for hormone-dependent conditions, such as endometriosis or prostate cancer, with less impact on mood and behavior.
Could this fragment lower sex hormone production slowly and reversibly, without first causing the spike that standard GnRH drugs produce?
Men starting standard GnRH drugs for prostate cancer get a temporary testosterone surge that can worsen symptoms. A drug that suppresses hormones gradually, without that initial spike, could make the start of treatment easier and reduce the need for additional flare-blocking medication.
▸full evidence table2 metrics
| metric | value | tool |
|---|---|---|
| ipTM | 0.9485611319541931 | boltz-2 |
| ranking score | 0.7920911312103271 | boltz-2 |
▸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{pep10733,
sequence = {SYGLRPG},
target = {gnrhr},
author = {peptidemodel},
year = {2026},
status = {computed}
}