Information alert

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The purpose of this information is to explain:

  • what GnRH-a is
  • the different types of GnRH-a available
  • why GnRH-a might be prescribed
  • the side effects of the medication.

This information is intended for patients who are receiving GnRH-a injections as part of their treatment under a gynaecology team.

Gonadotropin-releasing hormone analogue (GnRH-a) is a modified version of a natural hormone in the body called gonadotropin releasing hormone (GnRH). An injection of this hormone reduces the release of Follicle Stimulating Hormone (FSH) and Luteinising Hormone (LH) from the pituitary gland. Without FSH and LH, the ovaries do not get a signal to produce oestrogen and progesterone hormones. The ovaries stay inactive, and this puts a woman into a temporary (short term) state similar to menopause.

GnRH-a is a helpful treatment for women with many gynaecological conditions, including fibroids and severe endometriosis. It can also be used in preparation for gynaecological surgery.

At UCLH the common GnRH-a given is Prostap® (Leuprorelin acetate). (Other versions you may have heard of are Gonapeptyl® (Triptorelin) and Zoladex® (Goserelin)).

Prostap® (Leuprorelin acetate):

-3.75mg single injection-dose lasts up to 4 weeks.

-11.25mg single injection-dose lasts up to 12 weeks.

Most commonly, this is a short-term treatment, for example in preparation for surgery. For this reason, women are usually prescribed one or two doses (3–6 months of treatment). A small number of women may, after discussion with their doctor, be prescribed the medication for a longer period.

If you do take the GnRH-a medication for more than 6–12 months, you may be recommended to have a bone density test. This is because long-term use can thin your bones, though this can be prevented by giving ‘add back’ hormones (see below).

The lining of the womb, fibroids (knots of muscle fibres in the wall of the womb) and endometriosis (a condition where the tissue in the lining of the womb is found elsewhere in the pelvis) grow under the influence of hormones. Therefore when the production of oestrogen and progesterone by the ovaries is temporarily switched off with GnRH-a injections, it can have many benefits.

Reasons that you have been recommended to have GnRH-a may include:

  • to make surgery safer, especially in patients that have large fibroids or severe endometriosis
  • to allow a smaller incision to be made to remove fibroids or the womb during surgery (which has the benefit of a shorter recovery time)
  • to manage heavy vaginal bleeding and improve anaemia
  • to manage pain associated with menstrual cycles and endometriosis.

GnRH-a is not usually a long-term solution: once you stop taking it, your cycle will restart and your own hormones will stimulate growth of fibroids or endometriosis and bleeding again (unless, by then, you have naturally reached the menopause (when your ovaries naturally stop producing hormones).

GnRH-a can be given as a subcutaneous injection (just beneath the skin, normally in the stomach or arm) or as an intramuscular injection (in the thigh or buttock). You may be seen for repeat injections (every 1–3 months), or have just one dose in preparation for surgery.

After receiving the first GnRH-a, depending on where you are in your cycle, you may still have a period. Providing you take your follow up doses on time, you will usually not have a period again until you stop the injections.

After stopping the injection, periods generally return within a few weeks, although for some women it may take several months. The first few periods may be longer or shorter, or heavier or lighter than you are used to.

Side effects are similar to symptoms of the menopause and may include:

Very common (affecting more than 1 in 10 people):

  • sweating and hot flushes
  • headaches
  • difficulty sleeping
  • bone pain.

Common (affecting 1 in 10 to 1 in 100 people):

  • weight changes
  • irritability
  • mood swings and low mood
  • sleep disturbances and tiredness
  • bone and joint pain
  • low sex drive, vaginal dryness and difficulty reaching orgasm
  • nausea
  • breast tenderness or changes to breast size.

Some people experience a hard lump at the site of the injection, which can be uncomfortable. This should reduce within a week, but if it persists or looks infected (e.g. red & hot to touch, increased swelling, discharge or offensive smell) you should consult your doctor.

As with any medication, very rarely an allergic reaction may occur. Symptoms of this may include:

  • rash and/or itching all over your body
  • shortness of breath.

You should seek urgent medical attention at your local A&E if you experience any of these symptoms, and explain that you recently had a GnRH-a injection.

If you have severe menopause symptoms you can contact the doctor who prescribed you the medication for advice. They can assess whether you would benefit from a low dose hormone replacement therapy (HRT) tablet such as Tibolone – which can help with these side effects.

Tibolone is given as a tablet at a dose of 2.5mg daily. A few women may continue this combination of treatment (GnRH-a and Tibolone) long-term.

If you have a history of breast cancer, stroke or blood clots, certain HRT medications may not be suitable for you. You should ensure your doctor is aware of this at the time they prescribe it.

Whilst GnRH-a stops oestrogen production by switching off the ovaries, it is not a recommended form of contraception. It is advised that you use additional protection, such as condoms, to prevent a pregnancy whilst you are receiving treatment. Once you stop treatment you can start trying to conceive straight away should you wish. GnRH-a injections do not have any long-term effects on fertility.

There are several different gynaecology specialist clinics that refer patients for GnRH-a injections. The injection clinic is run out of the Gynaecology Diagnostic Unit (GDU) where a registered nurse administers the injection here. The nurse cannot prescribe or give clinical advice about your medical care.

If you need to discuss your care then please contact your own gynaecology team.

If you were referred from the Endometriosis Team:

Contact the Endometriosis team at:

Or telephone: 020 3447 2611

If you were referred from Gynaecology Diagnostic Unit (Clinic 3):

Contact the GDU team on: 020 3447 6515 (goes to voicemail, but leave a message and we will return)

Or email:

The waiting time for surgery can be variable, and depends on many factors, including the complexity of the operation, investigations required, and the waiting list for that team. Once a date has been allocated, you will be contacted by the admissions team.

If you wish to discuss your operation date please contact the admissions team on 020 3447 2507. Please leave a message with your name, hospital number and contact details and they will return your call.

Your referring clinician or team should have made you aware of the ongoing treatment plan following administration of GnRH-a. If this includes receiving subsequent doses of GnRH-a, you might need to schedule another appointment.

This can be done straight away after your injection at the Clinic 3 reception. Your nurse will inform you whether to book for a month or three months’ time.

The clinic code for the injection clinic is: DJ35E

If you wish to cancel or change your appointment this can be done by contacting the appointment centre:

Telephone: 020 3447 9393


These websites provide further information about GnRH-a and the conditions that it helps to manage:



The Patient Advice and Liaison Service (PALS) is a service that offers support, information and assistance to patients, relatives and visitors. The PALS office is located on Ground Floor Atrium,

Telephone: 020 3447 9975 Email:

Address: PALS, Ground Floor Atrium, University College Hospital, 235 Euston Road, London NW1 2BU

Gynaecology Diagnostic and Early Pregnancy Unit Elizabeth Garrett Anderson Wing

Clinic 3, Lower Ground floor 235 Euston Road

London, NW1 2BU

UCLH Main switchboard: 0845 155 5000

































Page last updated: 17 May 2024

Review due: 01 March 2025