In the decade between the ages of eight and 18, a girl's body changes into that of a woman. Girls often go through puberty before boys do.
This process is driven by the release of the hormone, oestrogen, which changes the external shape of a girl's body and makes the genital organs develop. Hormones are chemicals that make these changes happen and which influence how your glands and organs work. You might experience a growth spurt during this time, especially in early puberty. Usually by age 16 or 17, you will have reached your full height.
Your hips will grow wider during puberty. Hair will start to grow under your arms and around your genitals. You will also notice that you sweat more. Fine hair will grow on your arms and legs. Your breasts will grow larger and also change shape. Many teens, both boys and girls, will have problems with acne during this time. There is no need to suffer unnecessarily, as there are many treatments available that will make acne disappear. These are all changes on the outside of your body.
On the inside of your body, the changes are no less dramatic. At some stage, usually around the ages of twelve or thirteen, you will start having your periods. This is called menstruation and this is caused by your hormones.
Your ovaries release an egg, which travels down the fallopian tubes to the uterus. The uterus grows a thick lining of blood, preparing for a possible pregnancy. If you have sex with a man during this time, the egg could be fertilised and might attach itself to the lining of the uterus and the pregnancy will begin.
But if you haven't had sex, the lining will be shed through your vagina. This 'bleeding' will last for four to seven days and usually comes around every 24 – 32 days. Not everyone has the same length of menstrual cycle. In the first few years, your periods may not be very regular, but usually it settles down from there.
If your period suddenly stays away, it doesn't mean that you are definitely pregnant. If you haven't had sex, you can't be pregnant anyway. Stress, such as exams or family problems, heavy exercise, big changes in your life or illness, can all contribute to having irregular periods.
If you experience cramps, know that this is entirely normal and take some paracetamol. If it is still a problem, go and see the family doctor.
Your body will usually settle down to a 28-day (or thereabouts) hormonal cycle. Sometimes before your periods starts, you may feel depressed or short-tempered. This is normal and is called Premenstrual Tension (PMT). Take a look at the "I want to" section above to see what you can do about this.
Going through puberty is sometimes difficult, sometimes awkard. Sometimes you feel as if you don't know your own body anymore. This is all part of growing up and if it makes you feel any better, everyone feels like this at some or other time during these years. This won't last forever.
(Liesel Powell, Health24, July 2003)