What effects does it have?

What is it?

Medications that temporarily reduce production of sex hormones.

It's also known as Blockers, Hormone blockers, Goserelin, Zoladex, Triptorelin, Decapeptyl, Leuprorelin, or Prostap.

How long does it last?

GnRH agonists are available in four week, twelve week and six month forms. Prolonged use may have some effects that are permanent and cannot be reversed. GnRH agonists usually take around two weeks to take full effect.

More information


Taking GnRH agonists without also taking a sex hormone (e.g. oestrogen and/or testosterone) or inadequate levels of sex hormones can cause osteoporosis or early heart disease 1. If GnRH agonists are being used without an additional sex hormone, DEXA (bone density) scans which measure bone mineral density may be needed 2.


GnRH agonists do not provide reliable contraception 3. They do not remove the risk of making someone pregnant, and they do not remove the risk of becoming pregnant.

Gonadotropin releasing hormone (GnRH) agonists are medicines that cause the gonads (testes and/or ovaries) to stop producing sex hormones. GnRH agonists are considered to have an excellent side-effect profile with minimal side-effects compared to other alternatives 1.

Commonly used GnRH agonists in the UK are Goserelin (Zoladex), Triptorelin (Decapeptyl) and Leuprorelin (Prostap).

In people with testes, this produces an anti-androgenic effect (reduction in testosterone levels). GnRH agonists are the main antiandrogen treatment used in the UK as while they are much more expensive than other antiandrogens they have less side effects. As these medications cause an initial rise in testosterone levels for the first few weeks of use, sometimes a short course of cyproterone will also be given 4.

In people with ovaries, treatment with GnRH agonists reduces oestrogen and progesterone levels. This causes periods to stop, along with halting breast growth. They are normally used in the UK to prevent puberty instead of anti-oestrogens like anastrozole. Treatment with GnRH agonists is not normally necessary for people taking testosterone as testosterone normally adequately suppresses production of oestrogen.

People who do not have gonads (ovaries and/or testes) do not need to take GnRH agonists. This means that after orchidectomy or salpingo-oophorectomy, there is no longer any need to use GnRH agonists.

GnRH agonists are usually supplied in forms that are administered once every four weeks 5, twelve weeks 6, or six months 7.

GnRH agonists may cause erectile dysfunction in people with penises. If this is not desired, it can be treated with sildenafil, tadalafil or vardenafil.

Costs and funding

GnRH treatment is available to people with testes who have a formal diagnosis on the NHS. It is also used by the NHS to prevent puberty in under 18s, and sometimes in conjunction with testosterone treatment to stop menstruation (periods) 8.

You do not have to pay the full cost of medication you are prescribed on the NHS. You are not asked to pay anything at all in Northern Ireland, Scotland and Wales. In England, people are asked to pay a small charge for each item on their prescriptions. There are ways you can reduce or avoid this cost, which you can read about on the NHS website.

If you are using private gender services, the service will normally ask your GP to write you NHS prescriptions. Your GP may or may not agree to do this - it is up to them. NHS England have published guidance for GPs to help them make this decision, which you may wish to give to your GP. If your GP agrees to prescribe, the cost of your medication is the same as any other NHS prescription. If your GP does not, the private service can write you private prescriptions, which you will have to pay the full cost of.


  1. 1 Seal, Leighton J (2017) “Hormone Treatment for Transgender Adults,” in Bouman, W. P. and Arcelus, J. (eds.), The Transgender Handbook: A Guide for Transgender People, Their Families and Professionals, Nova Science Publishers Inc, pp. 227–249.
  2. 2 Murjan, Sarah and T’Sjoen, Guy (2017) “Access to Clinical Services and the Role of Primary Care,” in Bouman, W. P. and Arcelus, J. (eds.), The Transgender Handbook: A Guide for Transgender People, Their Families and Professionals, Nova Science Publishers Inc, pp. 189–200.
  3. 3 FSRH Clinical Effectiveness Unit (2017) “Contraceptive Choices and Sexual Health for Transgender and Non-binary People.” [online] Available from: https://www.fsrh.org/documents/fsrh-ceu-statement-contraceptive-choices-and-sexual-health-for/contraceptive-choices-and-sexual-health-for-transgender-non-binary-people-oct-2017.pdf
  4. 4 Seal, Leighton J (2007) “The practical management of hormonal treatment in adults with gender dysphoria,” in Barrett, J. (ed.), Transsexual and other disorders of gender identity: A practical guide to management, Radcliffe Publishing, pp. 157–190.
  5. 5 Electronic Medicines Compendium (2016) “Prostap SR DCS.” [online] Available from: https://www.medicines.org.uk/emc/medicine/24673
  6. 6 Electronic Medicines Compendium (2015) “Zoladex LA 10.8mg.” [online] Available from: https://www.medicines.org.uk/emc/medicine/8590
  7. 7 Electronic Medicines Compendium (2016) “Decapeptyl SR 22.5mg.” [online] Available from: https://www.medicines.org.uk/emc/medicine/24154
  8. 8 National Gender Identity Clinical Network for Scotland (2015) “Endocrine Management of Adult Transgender Patients.” [online] Available from: http://www.ngicns.scot.nhs.uk/wp-content/uploads/2015/07/NGICNS-Endocrine-Management-of-Adult-Transgender-Patients-v1.0.pdf

Errors and omissions

Is there something missing from this page? Have you spotted something that isn't correct? Please tweet us or message us on Facebook to let us know, or file an issue on GitHub.

Page last updated: July 2018