Reproductive & hormonal
Goserelin
A GnRH agonist implant that suppresses ovarian or testicular hormone production for one or three months.
What it is
Goserelin is a synthetic decapeptide GnRH agonist, delivered as a small subcutaneous implant (Zoladex) that releases drug over 28 days or 12 weeks. Continuous exposure desensitises the pituitary, shutting down sex-hormone production. It is licensed for prostate cancer, premenopausal breast cancer, endometriosis and thinning of the womb lining before surgery.
How it works
- 1
Binds pituitary GnRH receptors with high affinity.
- 2
Continuous stimulation desensitises the gland, so LH and FSH release falls.
- 3
Testosterone or oestradiol drops to castrate or postmenopausal levels.
- 4
The implant releases a steady dose, avoiding the peaks that would otherwise restore pulsatility.
- 5
Suppression is reversible when the implant is stopped.
What it's studied for
Reported and studied effects
- Castrate testosterone levels within three to four weeks
- Reduced relapse and improved survival when added to tamoxifen in premenopausal breast cancer trials
- Substantial reduction in endometriosis pain
- Reversible menopause-like state with bone loss during treatment
Research protocol notes
Research context onlyResearch context only - prescription medicine. A 3.6 mg implant every 28 days or a 10.8 mg implant every 12 weeks, placed subcutaneously in the abdominal wall, is the licensed pattern; endometriosis treatment is normally limited to six months because of bone density loss, and trials measure hormone suppression and bone mineral density at 6 and 12 months.
These figures are described so you can understand what researchers did. They are not a dose, a schedule, or a suggestion — and they are not a substitute for a doctor.
Possible side effects and contraindications
Safety profile
Possible side effects
- Hot flushes and sweats
- Reduced libido
- Bone mineral density loss
- Mood changes and fatigue
- Vaginal dryness
- Bruising or pain at the implant site
- Tumour flare at the start
Contraindications and cautions
- Pregnancy and breastfeeding
- Prior hypersensitivity
- In prostate cancer with spinal metastases, antiandrogen cover is needed during the flare
- Caution with drugs that prolong the QT interval
A side-effect list is never complete, and these are not the only situations that warrant caution. Anything unexpected, or anything you are unsure about, should be discussed with a doctor before use.
Evidence assessment
Large randomised trials in premenopausal breast cancer (ZEBRA and the Early Breast Cancer Trialists overview) and prostate cancer, with survival and endocrine endpoints.
References
- 01Jonat et al., Goserelin versus cyclophosphamide, methotrexate and fluorouracil as adjuvant therapy in premenopausal patients with node-positive breast cancer (ZEBRA), JCO 2002
- 02European Medicines Agency - Zoladex product information
References link to published literature, regulator pages or literature indexes. Where a link points to a search, it collects the peer-reviewed work on that molecule rather than a single study.
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