Genes
Research suggests that puberty begins with a single gene, called KiSS1, which is present in your body at birth.
Another gene called GPR54 lies dormant (inactive) in your body for many years until it is suddenly activated by special chemicals called kisspeptins, which are produced by the KiSS1 gene.
The process of puberty starts when the GPR54 gene sends signals to your brain and triggers a chain reaction in your body. An area of your brain called the hypothalamus signals to the pituitary gland (a pea-sized gland near the base of the brain) to release hormones that stimulate the ovaries (in girls) or testicles (in boys) to make sex hormones.
This chain reaction and release of hormones brings on the changes of puberty.
Hormones
The ovaries and testicles produce two sex hormones that are responsible for the changes that occur during puberty:
Testosterone is produced by the testes (testicles). In boys, it stimulates the development of the penis and testes and causes muscle growth and pubic hair growth. It is also responsible for lowering the voice.
Women and girls also have testosterone in their body, which is produced in small amounts by the ovaries to help maintain muscle and bone strength.
Oestrodiol is produced by the ovaries. In girls, it stimulates the growth of the breasts and female reproductive system, and helps to regulate the monthly menstrual cycle (periods).
Boys and men also have oestrodiol in their body, which is produced in small amounts by the brain and testes to help maintain bone density.
Triggers of puberty
It is thought that puberty may be triggered by environmental and genetic factors.
Studies have shown that on average, black girls start puberty earlier than white girls. But there is no evidence to show that black boys mature faster than white boys.
Diet and nutrition are also thought to be important factors, particularly in girls. Studies have shown that girls who are overweight or obese tend to start puberty earlier, while girls with a lower body weight tend to start later.
The recent rising trend of obesity in girls could explain why the average age of girls beginning puberty has been falling over recent years. However, it is not known why obesity does not have the same effect in boys.
There is a lot of uncertainty about why certain factors seem to trigger puberty. Research is ongoing in this area.
