Puberty is the name for the time when your child's body begins to develop and change as he or she moves from being a child to an adult. Usually, puberty starts between ages 8 and 13 in girls and ages 9 and 15 in boys. When your body is ready to begin puberty, your child's pituitary gland (a pea-shaped gland located at the bottom of your brain) releases special hormones which affect different parts of their body. Boys experience production of testosterone (a hormone that stimulates sexual development) and sperm, whereas girls start to develop breasts and experience production of another hormone called oestrogen, which prepare her body to start her menstrual cycle.

Some children experience puberty earlier or later than others. There are several possible reasons for this. Causes of early puberty (also known as precocious puberty) in girls may be diverse. In some cases it could be a problem in the brain, such as a tumour, a head injury or an infection such as meningitis. It could also be a problem with the ovaries or thyroid gland, or it may simply run in your family. Early puberty in boys is less common and more probably associated with an underlying medical problem.

Causes of late puberty may be just that your child is maturing slower than average, and often runs in families. It could also be due to malnutrition (due to illness or otherwise) or it could be a long-term medical condition known as hypogonadism, in which the person produces few or no hormones.​​