Gonadotrophin-Releasing Hormone Analogue (GnRH) injections

This leaflet will tell you about Gonadotrophin-Releasing Hormone Analogue (GnRH) injections (also known as Prostap). It will tell you about the reason the medication may be started, possible side effects and what will happen if you are started on the medicine.

Why have I been offered these injections?

Gonadotrophin-Releasing Hormone Analogue (GnRH) injections are used to help with several gynaecological conditions including:

• Endometriosis.
• Uterine Fibroids.
• Adenomyosis.
• Menorrhagia.
• Pelvic pain.
• Severe premenstrual syndrome.

The overall aim of the injections is to improve symptoms by reducing or stopping heavy menstrual bleeding (heavy periods), and managing the linked symptoms of pelvic pain. By doing this it will hopefully improve your quality of life.

These injections can also be used before having an operation as part of getting ready for surgery and to reduce risks such as heavy bleeding. It can also be used as part of a treatment to avoid surgery in some patients.

The reasons why these injections are used are different depending on each condition. The reasons will be discussed with you in detail at your appointment with the nurse or doctor.

Types of GnRH Analogue available and how they are given

The most used GnRH Analogue that is used in this Trust is called Prostap. This is normally given via an injection into the muscle in the buttock (bum) or in the top of the arm. It can also be given via injection into fatty tissue if necessary.

How do these injections work?

GnRH Analogues are a group of false hormones which cause a temporary menopause. By doing this the aim is to stop your periods and reduce other symptoms related to your periods. Such as helping with symptoms of pelvic pain or reducing fibroid size.

GnRH Analogues slow or stop the release of hormones called luteinizing hormone (LH) and follicle stimulating hormone (FSH) from your pituitary gland, which is a part of your brain. By stopping the release of these hormones the injections reduce the production of two female hormones, oestrogen and progesterone, from the ovaries. This will stop your periods and help with your symptoms.

When the medication is first given, there is an increase in oestrogen hormone. This means that you may have initial worsening of your symptoms. This may last for the first month of treatment. Once the first month is over the treatment should begin to help your symptoms.

What are the side effects?

Most of the side effects are related to decreased oestrogen levels and are similar to the side effects associated with menopause. These can include hot flushes, mood swings, night sweats, depression and vaginal dryness.

Long term use of GnRH injections may also increase the risk of osteoporosis, which is a condition that weakens the bones and increases the risk of fractures.

Blood sugar levels may be altered during treatment with GnRH Analogues, which might cause issues for diabetic patients and require more monitoring of the blood glucose levels.

You may develop severe rash, itching, or difficulty breathing. Although these are rare, they could be signs of a severe allergic reaction and you will need to seek immediate medical attention.

Very Common (may affect more than 1 in 10 people)

Difficulty sleeping, hot flushes, headaches and bone pain which are relieved with simple painkillers.

Common (may affect up to 1 in 10 people)

Weight changes, mood changes, depression, tingling in hands or feet, dizziness, nausea, joint pain, muscle weakness, breast tenderness, changes in breast size, vaginal dryness, swelling in the ankles or skin reactions at the injection site such as hardening, redness, pain, abscesses, swelling, nodules, ulcers and skin damage.

Uncommon (may Affect more than 1 in 100 people)

Loss of appetite, changes in how much fatty substance is in your blood (Cholesterol), altered vision, pounding heartbeats, diarrhoea, vomiting, abnormalities in liver blood tests, hair loss, muscle aches, fever, chills and tiredness.

If you experience any side effects, then please inform a member of your gynaecology team.

It is important to note that not all patients will get side effects and GnRH Analogue injections can reduce and improve symptoms caused by gynaecological conditions.

How can these side effects be managed?

As the side effects of GnRH Analogues are mainly associated with low oestrogen levels, these symptoms can be managed with the use of Hormone Replacement Therapy (HRT).

This can be given with the injections to prevent or reduce the side effects associated with the menopause and make treatment easier.

A low dose of a mixed HRT can be given. This is called Tibolone and is a tablet. Tibolone is broken down by the body to make substances which work similarly to oestrogen, progesterone and androgen (hormones). This dose of HRT is small therefore it does not reduce the effectiveness of the GnRH Analogue injection.

It is important to note that not every patient is suitable for HRT, and you do not need to have this if you do not want to. You can talk about this at your appointment with your nurse or doctor.

The most serious side effect of GnRH Analogue treatment is thinning of the bones (osteoporosis). If the injections are administered without HRT the risks increase and treatment can only be provided for 6 months.

This allows for your bones to rebuild strength between courses. The use of HRT has long term benefits in reduction of bone thinning and the risk of developing osteoporosis.

Where GnRH Analogue treatment is provided for long term management, a bone density scan will be carried out. Your consultant will decide how often this happens. It is done to check that your bone density is within the normal range.

When you are having your scan it is recommended that a 6 month treatment break takes place at this time.

How often will I need them?

Prostap 3.75mg is given as an injection which lasts for 4 weeks. Your doctor or nurse will let you know when you need your next injection and how long you will get the injections for.

Injection Clinics Appointments – what to expect?

Your clinic appointment will last between 15 to 30 minutes. The nurse will check for any allergies and what medications you are currently taking.

This is because some medications or allergies may mean you cannot have the injection. It would be helpful if you could bring any current medications to this appointment. An initial assessment will be carried out in your first appointment to check that you will be able to have the injection.

The nurse will also discuss any side effects that you may get. The appointment provides an opportunity to discuss any concerns you may have.

Pregnancy and Contraception

Before you have your first dose the doctor or nurse may ask you to provide a urine sample. This is to confirm that you are not pregnant before the injections are given. Injections will not be given if you are pregnant, and it is important that we identify any potential pregnancies beforehand.

Although the GnRH analogue injections aim to stop your ovaries from releasing eggs (ovulation) the injections are not licensed as a form of birth control (contraception).

You will be advised to use non-hormonal – barrier birth control, such as condoms or a diaphragm/cap whilst you are receiving this treatment to prevent a pregnancy.

How long can I continue on this management regime?

Depending on the specific condition of the individual, GnRH Analogue injections can be used long term.

However if you do, you might be advised to use HRT to reduce the risk of developing osteoporosis and treatment breaks might be encouraged at set intervals. 

What to expect when I stop having the injections?

Oestrogen levels will start to increase after the last GnRH Analogue injection starts to wear off.

The return of ovulation and menstrual periods should normally return with 6 to 10 weeks, however the longer the course of treatment the longer it may take for periods to return.

The side effects as a result of low oestrogen will start to reduce as the levels increase and the symptoms related to your condition such as heavy periods, pelvic pain and painful periods may return. There will be no negative impact on ongoing fertility once ovulation has returned.

If you stop taking GnRH Analogues around the time of your natural menopause you may find that your periods are far less frequent than before you started the treatment. If you have gone through the menopause whilst on GnRH analogue therapy your periods may not return. 

For more Information

Please speak to your doctor about this treatment if you have any further questions.

Women’s Outpatients Department – University Hospital of Hartlepool

01429 522865
Opening hours: 8.30am to 5.00pm (Monday to Friday)

Women’s Outpatients Department – University Hospital of North Tees

01642 624212
Opening hours: 8.30am to 5.00pm (Monday to Friday)

Royal College of Obstetricians and Gynaecologists

www.rcog.org.uk

Endometriosis UK

www.endometriosis-uk.org

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