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How will my body develop during puberty?

Being Trans

We have known for ever so many years that not everyone fits into the boy / girl, man / woman category, and your gender – whether you are a boy or a girl is not dictated by your genitals – it is set in your heart and brain and soul. Your identity is set from when you are conceived, but what about your body, how will that change as you grow up?

Being Created

When you are conceived, the egg and sperm from your parents join and then divide over and over again to make the millions and millions of cells that make you. Some cells make your arm, some your brain, your liver your kidneys – everything. It’s so clever!


The egg and sperm you were conceived from had 46 pairs of chromosomes each – these chromosomes tell your body how to make you and they include two ‘sex’ chromosomes. The egg had two X sex chromosomes, and the sperm you were conceived from had an X and a Y. You only get one from each parent to make you and that means that you could have got an XX combination or an XY combination. These sex chromosomes dictate which genitals you will develop as your cells are doing all that dividing and your organs are forming.

If you had a XX combination then when you developed in the womb, your body would have created a womb, ovaries, clitoris, vagina and a vulva. If you had received XY from your parents your body will develop a prostate gland, a penis and testicles. They actually all start as the same cells in your body but those ‘sex chromosomes’ decide which genitals will be created.

Body Parts

Most people who have a penis identify as a boy, and most people who have a vagina identify as a girl – but that is not always the case. Some girls have a penis and some boys have a vagina, and that is perfectly OK. It’s more than OK, it is gender diversity, it’s just that some people struggle to understand it.


When you start puberty, signals from the brain tell your gonads (your ovaries or testicles) to wake up and start producing hormones. Testicles start to produce testosterone, which typically leads to masculinisation of the body, while ovaries produce estrogen, which typically leads to feminisation. But that might not feel right for everyone and some people want to swap to have the opposite puberty, or even a bit of both types of puberty.


If you are a girl with testicles, you may prefer to have a female puberty, in which case you would need to take hormones to stop the brain signals to your testicles to stop testosterone production and then take estrogen medicine as a replacement. On the other hand, if you are a boy with ovaries, you may want to take hormone medication to prevent feminisation and instead take testosterone medication to make your body develop masculine features instead. The changes in your body shape, skin, and body hair during puberty all depend on whether estrogen or testosterone is predominant, and you can choose which suits you best.


For example, testosterone typically leads to the growth of the penis to its adult size in boys. However, if you are a girl who has a penis, then by switching off your testosterone, and taking estrogen, your penis and testicles will remain small. If you have ovaries and allow your body to feminise with estrogen, you will have monthly periods, but if you opt to have testosterone instead, your periods won’t start and your clitoris will grow – just like the penis does with testosterone (but not as big). The clitoris is the bit of the body that would have made a penis if you had had XY chromosomes and it responds to testosterone.


Estrogen and progesterone hormones are responsible for breast development and so if you don’t have those hormones because your body made testicles instead of ovaries, your breasts won’t grow. If you want them to grow then you will need to stop your body producing testosterone and give it estrogen and progesterone instead. Given the right chance and get the timing right, they will grow and develop just as if you had XX chromosomes. One thing though, the signals for the hormones that are needed for breast-feeding babies and making milk come from the womb, and if you don’t have a womb then that won’t happen, but then not everyone breast-feeds their children anyway.

Bones and Skeletons

Other aspects of your body, such as body shape, skeleton size, height, and the size of your hands and feet, are also all instructed by the hormones your body have during puberty, so make sure you get them right – don’t have too much or too little. The hormones tell your skeleton how much to grow, and how fast to grow and when to stop growing. They also tell your body where to store fat – it is fat that gives us our body shape and our face shape. Estrogen tells your pelvis to widen in case you want to get pregnant and carry a baby in there, and this, along with fat distribution, gives a curvy body shape.

Having a Family

If you want to have children in the future, having a womb and ovaries are needed to get pregnant, and if you wanted to get someone pregnant then you would need to have a penis and testicles. To carry a baby during pregnancy, you would need a womb, and surgeons haven’t really mastered that yet – but they are trying! If you don’t have these things then you can’t get pregnant, or get someone pregnant, but don’t forget that not everyone can. Remember, there are many ways to become a parent, and biological children are just one option. Explore all the possibilities and see what’s best for you and your future family.


Hormones also tell our bodies where to grow hair – facial hair, pubic hair, armpit hair and body hair – even eyebrow hair!. Estrogen gives us less hairy bodies while testosterone makes hair grow everywhere!


Of course our genes also have a massive part to play, those are the other 44 chromosomes that tell the body exactly how it will develop. The size of your clitoris, penis, feet, hands or breasts; your height and your shoe size, the amount of hair you have on your body, the colour of your eyes and hair and the size and shape of your nose – are all dictated by your chromosomes – you have your parents to thank or blame for that!


The timing of puberty is really important. Children usually start puberty around the age of 11 or 12 and that is a really good time. It is best not to be too young or too old when your body develops, so early teens is a good age. If you are going to take medicines to give you the opposite puberty then you should take time to make that decision but start thinking about it early. Some people say you should wait, but if you know you are ready then you should get going.

Once puberty has started you can decide whether or not to allow your natural puberty to continue or you can stop it by taking puberty blocker medicines. That can give you more time to think while stopping puberty changes happening. Whenever you are ready to decide you can then either stop the puberty blockers and allow your natural puberty to continue, or you can keep taking your puberty blockers and have the hormones that suit you and will give you the puberty that feels right for you. It’s your body and you should choose.

Some people find it hard to understand all this, and that’s OK as long as they leave you in peace to make your own choices. Because you and I understand it, and I know that because you have taken the time to read this. I wish you all the very best with your puberty, be your best self and live your best life!

Dr Helen Webberley

Founder of GenderGP

Updated on February 21, 2024

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