GnRH Agonists and Antagonists: Medicine Overviews
GnRH agonists such as leuprolide and antagonists such as cetrorelix, ganirelix and degarelix are approved peptide medicines. Their label uses, mechanisms and safety information.
Content last updated . This page has not been medically reviewed.
Two classes, one natural hormone
Gonadotropin-releasing hormone (GnRH, also written LH-RH) is a natural hormone. It triggers the pituitary gland to release luteinizing hormone (LH) and follicle-stimulating hormone (FSH). [1] Several approved medicines are peptide analogues of GnRH, meaning lab-made, modified versions. Leuprolide is described on its label as a synthetic nonapeptide (nine amino acids) analogue of natural GnRH. [2] Ganirelix is a synthetic decapeptide (ten amino acids) with high antagonistic activity against natural GnRH. [3]The two classes act in opposite ways at first. An agonist (leuprolide) first stimulates GnRH receptors, then with continuous use causes receptors to be downregulated and LH and FSH release to fall. [2] An antagonist (cetrorelix, ganirelix, degarelix) blocks the receptor: cetrorelix competes with natural GnRH for binding on pituitary cells, and degarelix binds reversibly to pituitary GnRH receptors. [1][4] See agonists and antagonists for the plain-language idea.
What the US labels approve (read 2026-10-22)
Only the labels below were read; other products and countries exist. Laws change, and this is not legal advice.| Product (as labeled) | Class | Use named on the label |
|---|---|---|
| Lupron Depot (prostate strengths) | Agonist | Advanced prostate cancer. First US approval 1989. [5] |
| Eligard | Agonist | Advanced prostate cancer. [6] |
| Lupron Depot 3.75 mg | Agonist | Endometriosis (with limits on duration with add-back therapy) and, before surgery, anemia from fibroids. [7] |
| Lupron Depot-PED | Agonist | Central precocious puberty in children. [2] |
| Fensolvi | Agonist | Central precocious puberty, age 2 and older. [8] |
| Cetrotide (cetrorelix) | Antagonist | Preventing premature LH surges in women having controlled ovarian stimulation. [1] |
| Ganirelix acetate injection | Antagonist | Same fertility-treatment use. [3] |
| Firmagon (degarelix) | Antagonist | Advanced prostate cancer. [4] |
EU (EMA, central authorization). Cetrotide is authorized to prevent premature ovulation in women having ovarian stimulation (authorized 1999). [9] Orgalutran (ganirelix) is authorized for the same purpose (2000). [10] Firmagon is authorized for advanced hormone-dependent prostate cancer (2009). [11] Other countries: not verified.
What the trials and labels show
- Prostate cancer, a hormone-lowering outcome. In a 620-patient open-label randomized trial, degarelix was compared with monthly leuprolide for one year. [4] Testosterone was suppressed to the "castration" level in 97.2% on degarelix and 96.4% on leuprolide. [4] This is a hormone-level result (a biomarker). It shows the drug does its hormonal job; it is not by itself a survival result. See biomarker changes vs meaningful outcomes.
- Early flare with agonists. The leuprolide label says testosterone can rise about 50% above baseline when treatment starts, and that patients should be watched for worsening prostate cancer symptoms in the first weeks. [5]
- Other uses. The label excerpts read list the approved uses above; this page does not summarize trial results for endometriosis, fibroids, fertility treatment or puberty.
Professional-care context
Labels state that fertility products should be prescribed by physicians experienced in fertility treatment, and the long-acting leuprolide depot must be given by a healthcare provider. [1][5] This page gives no schedules or advice about starting, stopping or switching; the prescriber decides.Off-label and promoted use
The label excerpts read do not support GnRH analogues as general "hormone balancing" or anti-aging products. Proper evidence not found in the labels and regulator pages read for such uses. For how approval categories differ, see approved vs off-label vs investigational use.Frequently asked questions
Is leuprolide a peptide?
Yes. The label describes leuprolide as a synthetic nonapeptide analogue of natural GnRH. [2]
What is the difference between a GnRH agonist and an antagonist?
An agonist first stimulates the receptor, then lowers hormone release with continuous use. [2] An antagonist blocks the receptor. [4]
Why is there a "flare" warning with agonists?
The leuprolide label says testosterone can rise about 50% above baseline at the start of treatment. [5]
Are these drugs used in fertility treatment?
Cetrorelix and ganirelix are approved in the US and EU to prevent premature LH surges or ovulation in women having ovarian stimulation. [1][3][9][10]
More details: evidence, limits and cautions
The details behind this page: cautions, limits of the evidence and where sources disagree. Open any note to read it.
How to read the evidence labels
Labels used on this page: approved medicine (a regulator has approved it for a named use) and established for what the labeled trials measured. Brand, ingredient and formulation are separate things: why they are not interchangeable.
Major safety information
- Heart and metabolism (prostate use). The leuprolide label reports raised risk of heart attack, sudden cardiac death and stroke in men on GnRH analogues, and possible hyperglycemia, diabetes and high lipids. [5] Degarelix can also lengthen the QT interval. [4]
- Bones (endometriosis use). The 3.75 mg label says the medicine induces a low-estrogen state that causes bone mineral density loss, some of which may not be reversible. [7] Duration with add-back therapy should not exceed 12 months. [7]
- Mood (children). Psychiatric events have been reported in patients taking GnRH agonists. [2]
- Pregnancy. The 3.75 mg label contraindicates it in pregnancy, and the cetrorelix and ganirelix labels contraindicate use in known or suspected pregnancy. [7][1][3] Cetrorelix is also contraindicated in lactation. [1]
- Allergy. Degarelix is contraindicated after a severe hypersensitivity reaction to it, and cetrorelix labeling notes hypersensitivity reactions including anaphylactoid ones. [4][1]
- Injection site reactions were among the most common effects with degarelix, along with hot flashes. [4]
References
- FDA label (DailyMed): Cetrotide (cetrorelix acetate for injection), EMD Serono. Read 2026-10-22.
- FDA label (DailyMed): Lupron Depot-PED (leuprolide acetate), AbbVie. Read 2026-10-22.
- FDA label (DailyMed): Ganirelix Acetate Injection, Organon. Read 2026-10-22.
- FDA label (DailyMed): Firmagon (degarelix), Ferring Pharmaceuticals. Read 2026-10-22.
- FDA label (DailyMed): Lupron Depot (leuprolide acetate) for advanced prostate cancer, AbbVie. Read 2026-10-22.
- FDA label (DailyMed): Eligard (leuprolide acetate), Tolmar. Read 2026-10-22.
- FDA label (DailyMed): Lupron Depot 3.75 mg (leuprolide acetate), AbbVie. Read 2026-10-22.
- FDA label (DailyMed): Fensolvi (leuprolide acetate), Tolmar. Read 2026-10-22.
- European Medicines Agency: Cetrotide, EPAR page. Read 2026-10-22.
- European Medicines Agency: Orgalutran, EPAR page. Read 2026-10-22.
- European Medicines Agency: Firmagon, EPAR page. Read 2026-10-22.