Bitesize has changed! We're updating subjects as fast as we can. Visit our new site to find Bitesize guides and clips - and tell us what you think!


Homeostasis and hormones

Sex hormones

Changes occur at puberty because of sex hormones produced by the testes in boys, and the ovaries in girls. Some changes happen to everyone, both boys and girls, while others happen in one sex only.

Here are some changes that happen to both boys and girls:

  • pubic hair grows
  • underarm hair grows

Here are some changes that happen to boys only:

  • voice breaks - gets deeper
  • hair grows on face and body
  • body becomes more muscular
  • testes and penis get bigger
  • testes start to produce sperm cells

Here are some changes that happen to girls only:

  • hips get wider
  • breasts develop
  • ovaries start to release egg cells - periods start

Fertility in humans can be controlled by the artificial use of sex hormones, including contraceptive pills and fertility drugs.

Back to Understanding ourselves index

BBC © 2014 The BBC is not responsible for the content of external sites. Read more.

This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.