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for the Treatment of Pelvic Pain & Fibroids (Decapeptyl / Zoladex)
Obstetrics & Gynaecology
GnRH analogue is a modified version of a hormone produced naturally by your body.
GnRH analogues are designed to ‘switch off’ the ovaries temporarily and create a ‘menopausal’ state. This is done by blocking the hormones that stimulate the ovaries to produce eggs and will only last as long as you are on the medication.
Examples of the GnRH given in this treatment include Decapeptyl (triptorelin acetate), Zoladex (gosarelin acetate) and Prostap (leuprorelin acetate).
GnRH analogues are offered to patients with gynaecological conditions that are affected by the hormones of the menstrual cycle.
GnRH analogues are usually given as an injection into a muscle such as the buttocks.
This may be a one-off injection or a course of injections (for example, once a month for 6 months).
You will have your first injection at the hospital and any further injections will be with your GP or practice nurse. Some preparations are also available as a nasal spray.
Currently, GnRH analogues are not licensed for use for more than 6 months due to concerns that the treatment causes thinning of the bones. In some cases, a Consultant Gynaecologist can agree to a more prolonged course of treatment however, you must be made aware of the risks. You should also be advised to have bone scans along with hormone replacement therapy (HRT).
As with most medications, GnRH analogues may produce unwanted side effects.
Very common (may affect more than 1 in 10 people)
Common (may affect up to 1 in 10 people)
Uncommon (may affect up to 1 in 100 people)
Frequency not known (how often they occur cannot be estimated from the available data)
These side effects are reversible and, in most cases, will stop when the treatment ends. You may be prescribed HRT during your treatment to replace what your body would normally be producing and this will reduce these side effects. If the side effect become too much, please contact the clinic for advice.
Allergic reactions to GnRH analogues are very uncommon, however, if you experience any of the following please seek medical attention immediately:
Following your first injection your body may try to compensate by increasing your hormones. This may last for around 2 weeks until your body adjusts to the medication. Your symptoms may feel worse during this time.
The medication will usually stop your periods but you may experience a vaginal bleed during the first month of treatment. This is known as a ‘hormone withdrawal bleed’ and will stop once your body has adjusted to the medication.
You should not have this treatment if you are pregnant, trying to conceive or breastfeeding. You will be asked to provide a urine sample at your appointment to ensure you are not pregnant when the treatment is given.
Although the injections work by stopping the menstrual cycle, it is not licenced as contraception. You should use barrier contraception (e.g. condoms or diaphragm) for the duration of your treatment.
Hormonal contraception must not be used during your treatment.
There is no long-term impact on fertility once the treatment is stopped and the menstrual cycle returns. However, a regular menstrual cycle may take 2-3 months to return. The longer you use - this treatment, the longer it may take for your periods to return to normal.
If you have any further questions you can contact us in the Gynaecology Clinic at Greenoaks, telephone: 01709 427641.
Produced by Mr R Faraj and Dr W Smith (ST5), September 2017. April 2014, April 2020.
Revised April 2020, July 2022. Revision due July 2024. Version:4.0
©The Rotherham NHS Foundation Trust 2022. All rights reserved.