Kid's Health topics



Hi there. I’m Dr Sarah.  I’m a friend of Dr Megs and also a Paediatric Endocrinologist.   I look after kids with hormone issues and diabetes.  This is the first of a couple of posts that I will be writing.



Puberty is a normal process we all go through at some time but is strangely dreaded by many parents!  My first post is about puberty in girls and I will follow up with another article about boys.

I’ll talk about normal, early and late puberty and a few other variants.


I’ll start with hormones. Hormones are chemicals made in one part of the body that go through the blood stream and send messages to other parts of our body.  During puberty, the body starts to make hormones that cause major physical changes.  Essentially there are two processes that happen around the same time: puberty and adrenarche.

Puberty is when the pituitary gland starts to make signal hormones (FSH and LH which may be familiar names to people who have had IVF treatment) that tell the ovaries to start working. The ovaries then make oestrogen which is the female hormone.  Oestrogen causes breast development as well as changes to the tissue of the vagina and external genitalia and makes the uterus (womb) mature.


Adrenarche is when the adrenal glands which sit above the kidneys start to make male hormones or androgens. This happens in girls and boys.  This causes pubic hair, underarm hair, acne and body odour.

More detail about puberty:


The first sign of puberty in girls is thelarche or development of breast buds. These are firm discs that can be felt below the nipples and areolae.  Some girls notice them first because they are tender.  They can fluctuate in size a bit in the beginning.  In girls who have weight problems it can sometimes be hard to distinguish fatty tissue from true breast tissue.

Growth spurt

For girls, the biggest growth spurt in height happens in the first year of puberty. On average girls will grow 8-9cm in that year as opposed to 5-6cm in years before that.


Menarche (the first period) generally happens around two years after breast development starts.


There is a wide range of what we consider to be normal timing for the start of puberty.  In girls the average time is around 11 years but anywhere between 8 and 13 years is normal.  In most girls, puberty (ie breast development) comes first but in about 30% adrenarche (eg pubic hair) will be before breast development.  The first period happens on average just before 13 years and is delayed if there are no periods at 15 years or 4-5 years after breast development has started.



If breast development, particularly with a growth spurt, starts before the 8th birthday we call this precocious puberty.  Most girls with precocious puberty have early activation of the pituitary gland.  This is called central precocious puberty.  In most cases, there is no underlying reason but in some girls, we do find an underlying cause.  In rare cases the ovaries start making oestrogen early without getting the signal from the pituitary gland.

We would recommend seeing your doctor if your daughter has breast development before 8 years.  Endocrinologists will normally do some tests to see why puberty has started early.  This might include an X-ray of the wrist and hand to look at bone maturity (bone age) and some blood tests.  Depending on what we find, sometimes we need to do other tests eg an MRI scan of the brain.  There is a treatment available for central precocious puberty. Some girls will have breast development before 8 years but have a normal growth rate and normal tests.  For those girls, early breast development is probably a normal variant.

Premature adrenarche

Most girls who have pubic hair before their 8th birthday have early or premature adrenarche.  This is considered to be a normal variant. We can only diagnose this once we have ruled out the other reasons for making male hormones in the adrenal glands earlier than usual.   Girls with premature adrenarche will generally be growing at a normal rate rather than quickly and will not have any other concerning findings.  We normally would do a bone age X-ray and some blood tests.  There is no treatment for premature adrenarche.

If girls have early pubic hair but also have rapid growth in height, deepening of the voice or enlargement of the clitoris then there is more likely to be an underlying reason.  We would normally suggest a more urgent referral by your GP.

Premature thelarche

Isolated breast development can be on one or both sides.   It is common in girls under 2 years but can occur later in childhood.  Premature thelarche is also considered to be a normal variant. Girls with premature thelarche will be otherwise well, growing at a normal rate and have no other changes of puberty.   We normally recommend a specialist review to make sure nothing else is going on.  In many cases, no tests are needed.



As mentioned above, puberty is delayed if there is no breast development at 13 years or no periods at 15 years.  The most common reason for delayed puberty is having a family history of delayed puberty.  This is known as constitutional delay in growth and development. This is another normal variant. Often the child’s mother will have had her first period later than average or their father or uncles will have kept growing well after they finished school or started shaving later than average.

Other times late puberty can be related to being underweight and either eating too little or exercising a lot. Examples include girls with eating disorders such as anorexia nervosa and elite athletes eg dancers who dance several hours per day.

Underlying medical problems can also cause late puberty so we look for these conditions when we see the girl and her family.

In rare cases delayed puberty can be due to a problem with the ovaries.  Girls with this sort of problem may have normal pubic hair development but delayed or absent breast development.

Some girls will have normal timing of breast development but no periods at the expected time. These girls should also be assessed to make sure there are no underlying problems.



There is wide variation in the normal start time for puberty.    If you notice changes in your daughter before 8 years or if your daughter has not started puberty by 13 years then you should see your GP. In most cases your GP will be able to do some tests and will refer her to see a Paediatrician or a Paediatric Endocrinologist.


Stay tuned for my upcoming post on “Puberty in Boys.”

Dr Sarah





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