Gender affirming hormone therapy

Oestrogen based GAHT (also called E-GAHT) consists of 2 types of medicines – a form of oestrogen and a medicine to block testosterone. Both are needed unless you've had surgical removal of your testicles (in which case a testosterone blocker isn't usually needed).

It can be used by trans women or non-binary people who were assigned male at birth.

Effects of E-GAHT

E-GAHT can lead to gradual changes over many months and years. There are some things it can't change (see below). Effects vary between individuals.

E-GAHT does NOT change the following:

• voice (your healthcare provider may be able to refer you for voice therapy)
• bone structure
• adams apple
• hair growth does not stop completely (some people use laser hair removal).

Note: contraception should still be used if you're having sex which could result in pregnancy.

You may hear about people using progesterone as part of E-GAHT, but currently there's not enough evidence for the benefit of using this as part of GAHT, so it's not generally recommended.

Oestrogen

Oestrogen is usually started at a low dose and gradually increased over the first year of therapy. There are a few forms of oestrogen funded in New Zealand:

• tablets
• patches
• gel (Estrogel from 1 November 2024)

Oestrogen injections are not funded in Aotearoa New Zealand. There's no evidence that oestrogen injections are more effective than the tablets or patches, and they may carry more risk because they can lead to higher oestrogen levels. For this reason, they're not part of national medical guidelines.

Oestrogen can cause blood clots (unless you use patches or gel), liver problems, raised cholesterol and breast cancer. The risks are higher if you smoke, are over 45 years of age or have a family history of certain health problems. Oestrogen patches and gel have a lower risk of blood clots than tablets.

Testosterone blockers

In Aotearoa New Zealand spironolactone tablets or cyproterone tablets are commonly used. Some people may use an injected implant (goserelin).

• Spironolactone works by blocking the effects of testosterone in the body, eg, by promoting breast growth and slowing down body hair. Spironolactone can change blood potassium levels so blood test monitoring is important especially if you have kidney problems. Read more about spironolactone.  
• Cyproterone works by stopping the release of testosterone. Cyproterone can cause side effects including low mood, weight changes, problems with your liver and meningioma (a non-cancerous brain tumour), so you should discuss this with a medical professional and use the lowest effective dose. Read more about cyproterone. 

For more detailed information about oestrogen and testosterone blockers, see Oestrogen-based gender affirming hormone therapy.(external link)

Examples of testosterone preparations

There are a few types of testosterone available for testosterone based GAHT (T-GAHT). It's usually given as an injection, but a patch and gel is available as well.

• Depo-testosterone – an injection every 1 to 2 weeks (you can be taught to self-inject this)
• Sustanon – an injection given every 3 weeks (you can be taught to self-inject this)
• Reandron – an injection given every 3 months (this must be given by a healthcare provider)
• Testosterone patches – these may cause skin irritation.
• Testosterone gel – applied once daily, usually in the morning. Read more about testosterone gel (Testogel).

T-GAHT can be used by trans men or non-binary people who were assigned female at birth.

Effects of T-GAHT

• Note: You could still become pregnant even if your periods have stopped. It's important to use contraception if you're having sex which could result in pregnancy because testosterone is harmful to a developing foetus. Read more about contraception below.
• Anyone with a cervix should discuss cervical screening with their healthcare provider.

To learn more about testosterone and it's expected effects, see testosterone-based gender affirming hormone therapy(external link).

Yes, if you're sexually active and want to avoid pregnancy, you should use contraception if you're using oestrogen based GAHT or testosterone based GAHT. Gender affirming hormone therapy doesn't prevent pregnancy.

If you're using T-GAHT, contraception is especially important. If you become pregnant while taking T-GAHT, this is harmful to the baby. If you wish to become pregnant you should stop testosterone first and discuss this with your healthcare provider.

Some people have problems becoming pregnant after being on T-GAHT. It's not known if this is due to testosterone, or if they would have had fertility problems for another reason. If you need advice on planning a pregnancy, talk to your healthcare provider. T-GAHT doesn't usually affect the quality of your eggs.

No, GAHT is not the same as puberty blockers.

GAHT refers to the hormones (oestrogen or testosterone) that are used by older adolescents or adults to help with development of physical changes which align with the gender you identify with. GAHT has some irreversible effects, meaning they can't be changed.

Puberty blockers (also known as GnRH agonists) are medicines used to pause the changes of puberty. This allows young people time and space to decide what is right for them as they get older. Some young people choose to stop puberty blockers allowing puberty to continue as it would have done. Others who experience persistent gender incongruence may explore whether GAHT is right for them so that they develop bodily changes in line with the gender they identify with.