FDA-approved
Sexual & reproductive
Goserelin
Goserelin (Zoladex) is an FDA-approved GnRH agonist implant. Learn how it lowers sex hormones and what it is used for in cancer and endometriosis.
- Reviewed by
- William Maish, MD MBA MPH, Clinical Product Lead
- Published
- October 5, 2026
- Last updated
- October 5, 2026
Key takeaway
Goserelin (goserelin acetate, sold as Zoladex) is a synthetic decapeptide agonist of gonadotropin-releasing hormone delivered as a small implant that suppresses the body's production of testosterone and estrogen. It is used across prostate cancer, breast cancer, and endometriosis, and in one long-term breast-cancer trial it matched standard chemotherapy for survival in certain premenopausal women. It has been FDA-approved in the U.S. since 1989 and is given as a monthly or three-month depot implant.
At a glance
| What it is | A GnRH (LHRH) receptor agonist peptide delivered as a subcutaneous implant |
| Approved for | Advanced prostate cancer, advanced breast cancer in pre/perimenopausal women, endometriosis, and endometrial thinning before ablation |
| Key fact | In the ZEBRA trial it was equivalent to CMF chemotherapy for disease-free and overall survival in estrogen-receptor-positive, node-positive premenopausal breast cancer |
| Route | Subcutaneous depot implant (monthly or every three months) |
| Evidence strength | FDA approved |
What is goserelin?
Goserelin, known generically as goserelin acetate and sold under the brand Zoladex, is a synthetic ten-amino-acid analog of gonadotropin-releasing hormone (GnRH, also called LHRH). GnRH is the hypothalamic signal that drives the pituitary to release luteinizing hormone and follicle-stimulating hormone, which in turn stimulate the testes and ovaries. Goserelin is a longer-acting, more potent version of that signal, formulated as a wax-like cylinder that is placed under the skin of the abdomen and releases drug slowly. It was first developed under the code ICI-118630 and approved in the United States in 1989.
How does goserelin work?
Goserelin binds the GnRH receptor on pituitary cells. A first dose briefly stimulates the pituitary, causing a transient rise in luteinizing hormone and sex hormones known as the flare. Because the implant then delivers drug continuously rather than in natural pulses, the receptors downregulate and desensitize, and within a few weeks luteinizing hormone and follicle-stimulating hormone fall. Testosterone in men, or estrogen in women, drops to castrate or postmenopausal levels.
Lowering those hormones is the point of treatment:
| Condition | Hormone lowered | Why it matters |
| Prostate cancer | Testosterone | Hormone-sensitive tumors depend on it |
| Premenopausal breast cancer | Ovarian estrogen | It can fuel estrogen-receptor-positive disease |
| Endometriosis | Estrogen, inducing a reversible low-estrogen state | The low-estrogen state shrinks lesions |
In the long-term ZEBRA trial, goserelin was equivalent1 to standard CMF chemotherapy for disease-free and overall survival in premenopausal women with estrogen-receptor-positive, node-positive early breast cancer, without chemotherapy's acute toxicity.
Is it FDA-approved?
Yes. Goserelin, originally developed by ICI Pharmaceuticals (later Zeneca, now AstraZeneca), was approved2 by the FDA in 1989. The implant is available in a 3.6 mg monthly strength and a 10.8 mg three-month strength, and the approved indications have broadened over time across oncology and gynecology.
What is goserelin prescribed for?
Goserelin is prescribed for:
- Advanced prostate cancer (alone or with radiotherapy or an anti-androgen)
- Advanced breast cancer in pre- and perimenopausal women
- Endometriosis
- Thinning of the endometrial lining before surgical ablation for heavy uterine bleeding
It is contraindicated in pregnancy because of its hormonal effects.
What are the side effects?
According to the prescribing information2, common side effects reflect reduced sex-hormone levels:
- Hot flashes and sweating
- Sexual dysfunction and vaginal dryness
- Headache
- Injection-site reactions
- Bone-density loss with long-term use
More serious considerations include:
- Disease "flare" early in prostate-cancer treatment, sometimes managed with an anti-androgen
- Increased risk of hyperglycemia and cardiovascular events with long-term androgen deprivation
- Rare pituitary apoplexy
More for sexual & reproductive
Sources: FDA prescribing information for Zoladex; the ZEBRA trial (Kaufmann et al., European Journal of Cancer, 2003, DOI: 10.1016/s0959-8049(03)00392-71), indexed on PubMed. This document is educational and does not constitute medical advice.