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Changes at puberty

Puberty/pūhuruhurutanga is a normal part of life – it is the process of becoming an adult and is caused by hormones produced in your body. Girls and boys experience different changes in their bodies during puberty.

What is puberty?

Puberty is the time when you start to change from being a child/tamaiti to a young adult/rangatahi.

Why does puberty start?

The changes in your body during puberty are caused by hormones which are chemicals produced in your body.

Showing the physical changes in the male body during puberty

These hormones are like chemical messages that cause the testicles or the ovaries to release other hormones.

All these hormones work together to start the changes in puberty.

When does puberty start?

There is no set age when this will happen. Puberty may start when you are eight or it may not start until much later.

In girls, puberty can starts anywhere between the ages of eight and 13 years old but often the first changes happen around 10 or 11 years of age.

In boys, puberty tends to start a little later than for girls - somewhere between 10 and 15 years. For many boys, the first changes start to happen when they are around 11 or 12 years old.

What are the hormones?

The main hormones during puberty are testosterone for boys and oestrogen and progesterone for girls.


During puberty your ovaries get bigger and your body will start to produce two hormones - oestrogen and progesterone.

Oestrogen causes your breast to grow and helps your vagina, uterus and fallopian tubes to develop. It also makes you grow taller and also changes the way fat is stored on your body making your waist, hips and buttocks more obvious.

After puberty, oestrogen and progesterone control your menstrual cycle or period.


For young men, the hormone testosterone is the hormone that starts development from boy to man.

Testosterone is the major male sex hormone and it is produced in the testes.

Testosterone levels rise significantly during puberty. When levels are high enough, testosterone starts the production of sperm, causes the chest and shoulders to broaden and causes facial hair to grow.

What physical changes happen during puberty?

During puberty you can expect a lot of changes to your body. Your genitals will get bigger.

In girls the breasts will grow and your vagina, uterus and fallopian tubes will develop.

In boys the penis and testes will get bigger. Boys will get erections more frequently.

Both boys and girls will get:

  • taller, heavier and stronger
  • an increase in sweating
  • more oily skin
  • hair growing around their genitals, under their arms and on their legs and arms.

Showing the physical changes in the female body during puberty

The influx of hormones during puberty can cause a range of feelings or emotions in both young women and young men and these feelings can change often. You might get:

  • sudden mood changes
  • changing emotions
  • an involuntary increase in sexual feelings and fantasies.

Are there changes that only happen to girls?

Girls’ bodies increase in size and shape during puberty. Their hips become more rounded and they get a more defined waist. The vulva, vagina and nipples get bigger and the breasts begin to develop, sometimes unevenly.

Other changes include pubic hair appearing and a vaginal discharge - an increase in the mucous produced in the vagina.

Girls also start menstruating or having their period during this time.

Are there changes that only happen to boys?

Boys’ bodies also change during puberty.

Their shoulders and chests become broader and their muscles get bigger. They may have a temporary swelling of the breasts as their hormones sort themselves out.

Hair starts to grow on the face and sometimes the chest.

Their voices get deeper and may go up and down or sometimes sound quite croaky all in one sentence.

The penis and testicles will get bigger; they have more erections, sometimes for no reason. Boys testicles usually start producing sperm between 11 and 16 years - at the time they start to grow pubic hair.

They start to ejaculate and/or reach orgasm when masturbating and some boys will have wet dreams.

What is menstruation?

Menstruation is more commonly known as a period – it is a normal and healthy part of being a female.

Girls usually get their first period between nine and 14 years, generally when they weigh about 41 kilos and are about 149 cm tall.

Periods are sometimes irregular at first, but usually settle into a pattern after a few months. If you haven't started your period by the time you are 16, it would be a good idea to talk to a nurse or doctor.

The amount of blood that is lost during your period is small (only about three tablespoons) and this will happen gradually over your period.

How often will I get my period?

Your period will last somewhere between three and seven days. Some girls have short periods and others have periods that last a little longer.

The time between the start of one period and the next is called the menstrual cycle. 

The menstrual cycle usually lasts about 28 days. This means there are 28 days between the start of your last period and the start of your next period. Cycles can be longer or shorter than this.

What does it mean when I get my period?

Once you start having your period, it means you are physically able to become pregnant.

What happens to my body during the menstrual cycle?

During puberty, your female reproductive organs begin to develop. When females are born, there are hundreds of thousands of eggs (ova) inside their ovaries.

When you’ve reached puberty, each month these hormones will cause an egg to start maturing and be released from the ovary. This process is called ovulation.

The egg moves along the fallopian tube towards the uterus. At the same time, the lining of the uterus becomes thick and soft with blood and tissue. This happens just in case the egg is fertilised. It would then implant itself into the lining of the uterus and grow.

Fertilisation only happens if the egg joins with a sperm from a male. More often than not, the egg isn’t fertilised so it is just reabsorbed back into the body.

When the egg is not fertilised, the lining of the uterus is not needed so it comes away and is released through your body through your vagina.

This is what is called menstruation or a period.

Family Planning has clinics located throughout New Zealand. Use the clinic finder to find your nearest clinic.

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