How is goserelin different from a daily injection?

It is a subcutaneous depot implant placed by a clinician that releases drug over 1 or 3 months, avoiding daily dosing.

Does it cause an initial flare?

Yes; like all GnRH agonists it briefly raises sex hormones before suppressing them, which is why anti-androgen flare cover is used in prostate cancer.

What are the key side effects?

Hot flushes and, with longer use, bone mineral density loss; men on androgen deprivation also face cardiometabolic considerations.

Can it protect fertility during chemotherapy?

In the POEMS trial, goserelin during breast-cancer chemotherapy reduced ovarian failure and improved later pregnancy outcomes, though it is not a guarantee of fertility.

EMA-approvedaka Zoladex

Goserelin — Complete Research Guide (2026)

Last updated 2026-06-30

TL;DR

Goserelin (also known as Zoladex) is a peptide catalogued under Sexual Health (GnRH agonist). It is described as: GnRH receptor agonist. Documented context: Prostate/breast cancer; endometriosis. Neutral reference entry; EU status: EU-approved prescription medicine.

What is Goserelin?

Goserelin (goserelin acetate; brand Zoladex) is a long-acting GnRH-agonist decapeptide analog delivered as a subcutaneous implant.

It is an approved human therapeutic used in advanced prostate cancer, hormone-receptor-positive breast cancer and ovarian suppression, endometriosis, and endometrial thinning before surgery; approvals vary by region.

Evidence level is high, anchored by large randomized controlled trials in both prostate and breast cancer.

How does Goserelin work?

Like other GnRH agonists, continuous receptor occupancy first stimulates then desensitizes pituitary gonadotrophs, initially raising and then suppressing LH and FSH.

The resulting fall in testosterone (men) or estradiol (women) removes the hormonal stimulus driving hormone-sensitive tumors and estrogen-dependent conditions such as endometriosis.

What does the research say about Goserelin?

Adding long-term goserelin to radiotherapy improved 10-year overall and prostate-cancer-specific survival versus radiotherapy alone in high-risk, locally advanced disease. ^[1]
In premenopausal breast cancer, ovarian suppression with goserelin added to endocrine therapy reduced recurrence in higher-risk women. ^[3]
Goserelin given during adjuvant chemotherapy lowered rates of ovarian failure and improved subsequent pregnancy outcomes. ^[4]

Clinical research & studies

The references below are the primary sources cited throughout this guide. Each links directly to PubMed or the regulator. Where evidence is preclinical (animal or in-vitro), that is stated rather than implied.

[1] External irradiation with or without long-term androgen suppression for prostate cancer with high metastatic risk: 10-year results of an EORTC randomised study — Bolla M et al., Lancet Oncology 2010. (Randomized controlled trial)
[2] Long-term results with immediate androgen suppression and external irradiation in patients with locally advanced prostate cancer (an EORTC study): a phase III randomised trial — Bolla M et al., Lancet 2002. (Randomized controlled trial)
[3] Adjuvant ovarian suppression in premenopausal breast cancer — Francis PA et al., New England Journal of Medicine 2015. (Randomized controlled trial (SOFT))
[4] Goserelin for ovarian protection during breast-cancer adjuvant chemotherapy — Moore HC et al., New England Journal of Medicine 2015. (Randomized controlled trial (POEMS))
[5] Comparison of the gonadotropin-releasing hormone agonist goserelin acetate alone versus goserelin combined with estrogen-progestogen add-back therapy in the treatment of endometriosis — Kiilholma P et al., Fertility and Sterility 1995. (Randomized controlled trial)

Dosing context

This is not medical advice or a usage recommendation. Dosing figures are reported research context only, cited from the published literature.

Goserelin is supplied as a clinician-inserted subcutaneous depot implant (commonly 3.6 mg monthly or 10.8 mg every 12 weeks), with the formulation chosen by indication.

This is context only, not a dosing recommendation; regimens must be individualized and prescribed by a qualified clinician.

Side effects & safety profile

As with the class, treatment starts with a transient hormonal flare (rising testosterone/estradiol in the first weeks) that can briefly aggravate prostate-cancer symptoms before suppression takes effect.

Predominant adverse effects are those of induced hypogonadism: hot flushes and vasomotor symptoms and, with prolonged use, reduced bone mineral density; androgen-deprivation therapy in men also carries cardiometabolic considerations.

It is prescription-only, administered by a clinician, and contraindicated in pregnancy.

Stacking & combinations

In prostate cancer a short course of an anti-androgen is typically added around initiation to cover the testosterone flare; in benign gynecologic use, estrogen/progestin add-back is used to protect bone and reduce menopausal symptoms.

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Frequently asked questions

It is an approved medicine for advanced prostate cancer, hormone-receptor-positive breast cancer and ovarian suppression, endometriosis, and endometrial thinning, depending on region.

References

[1] External irradiation with or without long-term androgen suppression for prostate cancer with high metastatic risk: 10-year results of an EORTC randomised study — Bolla M et al., Lancet Oncology 2010. PMID: 20933466. View sourceStudy: Randomized controlled trialLong-term androgen suppression with goserelin added to radiotherapy improved 10-year overall and disease-specific survival.
[2] Long-term results with immediate androgen suppression and external irradiation in patients with locally advanced prostate cancer (an EORTC study): a phase III randomised trial — Bolla M et al., Lancet 2002. PMID: 12126818. View sourceStudy: Randomized controlled trialGoserelin plus radiotherapy improved survival versus radiotherapy alone in locally advanced prostate cancer.
[3] Adjuvant ovarian suppression in premenopausal breast cancer — Francis PA et al., New England Journal of Medicine 2015. PMID: 25495490. View sourceStudy: Randomized controlled trial (SOFT)Adding ovarian suppression to endocrine therapy reduced recurrence, particularly in higher-risk premenopausal women.
[4] Goserelin for ovarian protection during breast-cancer adjuvant chemotherapy — Moore HC et al., New England Journal of Medicine 2015. PMID: 25738668. View sourceStudy: Randomized controlled trial (POEMS)Goserelin during chemotherapy reduced ovarian failure and improved pregnancy rates.
[5] Comparison of the gonadotropin-releasing hormone agonist goserelin acetate alone versus goserelin combined with estrogen-progestogen add-back therapy in the treatment of endometriosis — Kiilholma P et al., Fertility and Sterility 1995. PMID: 7589632. View sourceStudy: Randomized controlled trialAdd-back therapy maintained efficacy against endometriosis while reducing hypoestrogenic side effects.

This article is for educational and research purposes only. Peptides discussed here are not approved for human consumption by the FDA, EMA, or equivalent regulators outside of specific clinical contexts. Always consult a licensed medical professional before any therapeutic use.