What Is Buserelin? Definition and What Research Reports

Definition

Buserelin is a synthetic nonapeptide analogue of gonadotropin-releasing hormone (GnRH), the hypothalamic decapeptide also referred to as luteinising hormone-releasing hormone (LHRH). It belongs to the class of GnRH agonists — molecules built on the native GnRH sequence with amino-acid substitutions that increase receptor affinity and resistance to enzymatic breakdown. Buserelin is most often handled as the salt buserelin acetate. Like the parent hormone, it binds GnRH receptors on pituitary gonadotroph cells and stimulates release of luteinising hormone (LH) and follicle-stimulating hormone (FSH); with continued exposure, that same receptor engagement leads to desensitisation and downregulation, which is why agonists of this class are described in the literature as producing an initial stimulatory phase followed by suppression.

This page is for educational purposes only and is not medical advice; consult a licensed physician for any question about medical treatment or a health condition.

What Class of Molecule It Is and Where It Comes From

Buserelin is not extracted from tissue. It is a chemically synthesised peptide modelled on the naturally occurring GnRH sequence, with modification at the position-6 residue and a substituted C-terminus — the general design strategy shared across GnRH agonists. Because it is a short peptide rather than a small molecule, it is poorly absorbed through the gut and is studied after parenteral routes; intranasal and depot formulations also appear in the reproductive-medicine literature.

In terms of naming, readers will encounter several labels for the same underlying molecule:

• Buserelin — the free peptide, international nonproprietary name.
• Buserelin acetate — the acetate salt form used in most formulations and in the veterinary literature, including the tambaqui spawning-induction work (PMID 32931986).
• GnRH agonist / LHRH agonist — the pharmacological class descriptor used interchangeably in older papers.
• Receptal — one veterinary product name under which buserelin acetate has been evaluated pharmacokinetically in gilts (PMID 41313143).

How the Term Is Used in Peptide Research

In the published literature, "buserelin" appears in four broad research contexts. First, human assisted-reproduction protocols, where GnRH agonists have historically been compared with GnRH antagonists during ovarian stimulation. Second, veterinary reproduction, where buserelin is one of several GnRH analogues studied for ovulation induction and oestrous synchronisation in cattle, sheep, horses, pigs and fish. Third, pharmacokinetic characterisation across species. Fourth, mechanistic and toxicology-adjacent animal work, where repeated buserelin administration has been used as a model system to study downstream effects on non-reproductive tissue.

Because the compound has a long veterinary history, a large share of the buserelin literature is livestock-based rather than human-based — a point worth keeping in mind when interpreting any single finding.

What the Published Literature Reports

Human reproductive medicine

A prospective randomised phase III European study compared the LHRH antagonist cetrorelix with the LHRH agonist buserelin during ovarian stimulation with human menopausal gonadotrophin (HMG), and the researchers reported outcomes for the two approaches within an in-vitro fertilisation setting (PMID 10686191). That trial is one of the reference points frequently cited when the agonist-versus-antagonist distinction is explained.

Endocrine and reproductive responses in animals

In rams, a study examined buserelin administration and reported effects on testicular blood flow alongside plasma concentrations of testosterone and estradiol-17β (PMID 34175682). In cattle, researchers compared gonadorelin, lecirelin and buserelin and reported differences in the LH surge, ovulation and subsequent progesterone (PMID 25890780). A separate study in dairy cows with anovulation type I evaluated repeated low doses of the GnRH analogue buserelin and reported fertility-performance outcomes (PMID 37389450). In anoestrous mares, retinol and cholecalciferol were reported to affect buserelin-induced oestrus (PMID 40095200). In fish, buserelin acetate was used for hormonal induction and the study reported that tambaqui females (Colossoma macropomum) spawned following induction (PMID 32931986).

Pharmacokinetics

A veterinary pharmacokinetic study characterised buserelin after intramuscular administration in pigs and cows (PMID 35410205), and a later evaluation described the pharmacokinetics of buserelin acetate (Receptal) in gilts (PMID 41313143). These papers are the usual citations when species differences in exposure are discussed.

Non-reproductive and mechanistic work

A 2025 immunology paper reported that buserelin promoted the differentiation and function of macrophage-colony-stimulating-factor-producing T helper cells (PMID 39495003), an example of buserelin being used as a probe outside the reproductive axis. In mice treated with cyclophosphamide, a study examined glutathione and buserelin and reported stereological parameters of the hypothalamus (PMID 33039509).

Buserelin in Animal Models: What Studies Report

The most frequently referenced adverse-effect literature for buserelin comes from a rat enteric-neuropathy model. Researchers reported structural and functional consequences of buserelin-induced enteric neuropathy in the rat (PMID 25496312), and a follow-up paper described long-term outcomes of buserelin-induced enteric neuropathy in rats (PMID 26935850). These are animal studies designed to characterise a model, and their findings are not statements about outcomes in humans; they are cited here because they are part of the published buserelin record.

The hypothalamic stereology work in cyclophosphamide-treated mice similarly sits in the mechanistic-animal category rather than the clinical one (PMID 33039509).

Quick Reference

Related Terms

• GnRH / LHRH — the endogenous decapeptide buserelin is modelled on.
• GnRH agonist — class including buserelin, gonadorelin and lecirelin, the latter two compared with buserelin in cattle (PMID 25890780).
• GnRH antagonist — class including cetrorelix, compared with buserelin in a randomised European study (PMID 10686191).
• Downregulation — the receptor desensitisation that follows sustained agonist exposure.

Limitations of the Evidence

Much of the recent buserelin literature is veterinary or preclinical, and findings in rams, cattle, gilts, mares, mice, rats or fish do not transfer directly to humans. Species differ in GnRH receptor pharmacology and in peptide clearance, which is precisely why separate pharmacokinetic evaluations were performed in pigs and cows (PMID 35410205) and in gilts (PMID 41313143). Readers comparing papers should note the species, formulation and route before drawing any conclusion. Regulatory status also varies by jurisdiction and by whether a given product is authorised for human or veterinary use.

References

• Buserelin Promotes the Differentiation and Function of Macrophage-Colony-Stimulating Factor-Producing T Helper Cells (Immunological Investigations, 2025)
• Long-term follow-up of buserelin-induced enteric neuropathy in rats (Molecular Medicine Reports, 2016)
• Effects of buserelin administration on testicular blood flow and plasma concentrations of testosterone and estradiol-17β in rams (Domestic Animal Endocrinology, 2021)
• Tambaqui females (Colossoma macropomum) spawn after hormonal induction with buserelin acetate (Animal Reproduction Science, 2020)
• The pharmacokinetics of buserelin after intramuscular administration in pigs and cows (BMC Veterinary Research, 2022)
• Structural and functional consequences of buserelin-induced enteric neuropathy in rat (BMC Gastroenterology, 2014)
• Ovarian stimulation with HMG: results of a prospective randomized phase III European study comparing the LHRH-antagonist cetrorelix and the LHRH-agonist buserelin (Human Reproduction, 2000)
• Pharmacokinetic Evaluation of Buserelin Acetate (Receptal) in Gilts (Journal of Veterinary Pharmacology and Therapeutics, 2026)
• Effect of repeated low doses of GnRH analogue (buserelin) on fertility performance of dairy cows with anovulation type I (Polish Journal of Veterinary Sciences, 2023)
• Effect of gonadorelin, lecirelin, and buserelin on LH surge, ovulation, and progesterone in cattle (Theriogenology, 2015)
• Retinol and cholecalciferol affect buserelin-induced estrous in anestrous mares (Tropical Animal Health and Production, 2025)
• The effect of glutathione and buserelin on the stereological parameters of the hypothalamus in the cyclophosphamide-treated mice (Journal of Chemical Neuroanatomy, 2020)