In last week’s blog we covered puberty in girls. This week it is time to talk about boys. There are some similarities between boys and girls with puberty but many differences, hence the separate posts.  Where there are similarities I’ve included some of the same details in this post so that you don’t have to read the article about girls if it is not relevant for you.

WHAT IS PUBERTY?

As we discussed last week, 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) that tell the testes to start working. The testes then make testosterone which is the main male hormone.  Testosterone causes many physical changes which will be discussed below.

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

More details about puberty:

The first sign of puberty in boys is an increase in the volume of the testes to 4mL.  This happens before the other physical changes in boys so can be subtle.  Doctors can estimate the size of the testes by comparing them to a set of beads called an orchidometer.

After the testes start to get bigger and make testosterone, boys will start to notice other changes of puberty including growth of the penis and scrotum and development of pubic and underarm hair. Other changes include a growth spurt, deepening of the voice, an increase in muscle mass and an increase in facial and body hair.  The testes will continue to get bigger throughout puberty as they develop further and they start to make mature sperm from the middle of puberty onwards.  The whole process takes a few years although it can take several more years until an adult male hair distribution is achieved.

Growth spurt

Unlike girls who have a big growth spurt in the first year of puberty, boys will have their growth spurt a little later, around 13-14 years.  During that year, boys will grow on average 9-10cm as opposed to 5-6 cm per year in the years before.

TIMING

There is a wide range of what we consider to be normal timing for the start of puberty.  In boys the average time is between 11 and 12 years but anywhere between 9 and 14 years is normal.

EARLY PUBERTY

Changes of puberty before 9 years are considered to be early in boys.  Boys and their families may notice pubic hair or enlargement of the penis.  These changes could be due to early puberty (ie testosterone production by the testes) or early adrenarche (male hormones being made in the adrenal glands).  The main indicator that puberty has actually started is that the testes have started to enlarge. This is something that most boys would not necessarily notice in the early stages.

Similar to girls, most boys with early puberty have early activation of the pituitary gland, known as central precocious puberty.  In most cases there is no underlying reason but in some boys, there is an underlying cause. In rare cases the testes start making testosterone earlier than usual without getting the signal from the pituitary gland.

We suggest seeing your doctor if you notice changes of puberty under the age of 9 years in your son.  Doctors will usually do some tests to try and help work out what is happening. This usually includes an X-ray of the left wrist and hand to look at bone maturity (bone age) and some blood tests first thing in the morning.  Depending on what we find, sometimes we need to do other tests such as an MRI of the brain.  There is a treatment available for central precocious puberty.

Premature adrenarche

Pubic hair development under the age of 9 years without any other changes of puberty may be due to early or premature adrenarche.  This is a normal variant but we can only diagnose this once we have ruled out the other causes of early production of male hormones. In premature adrenarche, the testes will not be enlarged, the growth rate will be normal and there will be no other changes such as deepening of the voice.   When assessing a boy with suspected premature adrenarche, doctors will normally request some tests including a bone age X-ray and some blood tests.

Virlisation

In rare cases, there will be changes such as significant enlargement of the penis, a lot of pubic hair development, deepening of the voice and a big growth spurt in a young boy who still has small testes.  This is more concerning and your doctor will normally arrange an urgent referral to a Paediatrician or Paediatric Endocrinologist.  Doctors will normally do a number of tests to find out what part of the body is making the male hormones.  The treatment will depend on the cause.

PUBERTAL GYNAECOMASTIA (BREAST DEVELOPMENT)

People are often surprised to hear that as many as 50% of boys will have some breast development during puberty.  This is totally normal.  For most boys these are just small breast buds (firm discs of breast tissue below the nipples and areolae). They generally get better and go away with no treatment as puberty progresses.  It mostly is not due to any hormone problems so hormone treatments do not help.

In rare cases, breast development is quite pronounced and does not improve as puberty progresses. If this happens you should see your doctor to see if there could be an underlying medical problem such as a chromosomal problem.   Plastic surgeons will also sometimes see boys like this who are very distressed by the appearance of their breasts.

Boys with weight problems may have the appearance of breasts due to fatty tissue without having significant breast development.

Breast development before puberty has started in a boy is abnormal and these boys should definitely see their doctor to get checked out.

LATE PUBERTY

In boys, puberty is delayed if there are no signs of puberty at 14 years.   Like in girls, 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 and is a normal variant.  Often the boy’s mother will have started periods later than average or his father or uncles may have grown well after finishing school or started shaving much later than average.  Unfortunately, many boys experience significant teasing or bullying at school about being shorter than average or having late puberty.  Doctors will normally look for underlying medical problems to see if something else could be contributing to late puberty.  We will also examine the boy.  Sometimes we will actually notice early changes of puberty, eg enlargement of the testes, so can reassure the boy that puberty has started and will continue to progress on its own.  If there are no underlying medical issues, reassurance is all that is needed in most cases.  In some cases, doctors will prescribe a short course of testosterone treatment to kick start some of the changes of puberty.

Other times late puberty can be related to being underweight and eating too little or exercising a lot. This is less common in boys than girls but examples include children with eating disorders and elite athletes.

Underlying medical problems can also cause late puberty so doctors will look for these conditions when seeing the boy and his family.

In rare cases, delayed puberty can be due to a problem with the testes.

SUMMARY

As in girls, there is a wide variation in the normal start time for puberty in boys.  If you notice changes of puberty before 9 years in your son or if puberty has not started by 14 years then you should see your General Practitioner (GP).  In most cases your GP will be able to do some tests and will refer him to see a Paediatrician or Paediatric Endocrinologist.