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Hormones are chemical substances made by special glands and which pass all over the body through the bloodstream.

Hormones have powerful effects on things like metabolism, growth and development, sexual reproduction and the body’s responses to stress.

Hormones are important for making sure different parts of the body work together, and for regulating the activity levels of most of the organs, including gut, heart, liver and brain.

Some act only in the short-term – for example, after you have eaten, or when you are confronted with an ‘emergency’ situation (eg being threatened).

Others have much longer term effects, including controlling your metabolism, growth, and the onset of puberty.

Hormones and puberty

The marked changes in the body and in the way we behave at puberty are entirely due to hormones.

The testis in the male, and the ovaries in the female become active, and secrete testosterone or oestrogens respectively. These hormones are mostly responsible for young people developing from children into young adults.

Puberty is a time of great change. Not only does the body alter from a child-like shape to a more adult one, but things like friendships, attitudes to others (of both sexes) and to one’s parents all change quite dramatically.

Hormones also get blamed for lots of other things around puberty – mostly bad things, like acne, moodiness, tiredness, bad temper, greasy hair, sleeping a lot.


Testosterone is the most famous hormone of them all! There’s a great surge in the blood levels of testosterone at puberty.

It's responsible for ‘male’ bodily features like the growth of facial and pubic hair, muscle development, and some say, the aggressive and ‘show-off’ behaviour of some boys.

Girls also have some testosterone, but much less than boys. This doesn’t mean it’s less important. Just as in boys, testosterone is important for sexual feelings and responses.

Little children have hardly any testosterone. But in the womb, a boy’s testis does produce testosterone, and this is thought to have a very important role in producing a ‘male’ brain. For example, males are typically better at spatial things (eg maps) than girls; girls are better at words. Little boys play different sorts of games (typically rougher ones) than girls, and this may be because their brains have been exposed to testosterone in the womb. Some differences between the sexes in later life may result from testosterone in the womb, or the way it sensitises the brain to levels of testosterone after puberty.