Puberty - Causes of puberty

Puberty is started by certain genes and hormones in the body.

It's not yet fully understood why some people experience puberty earlier or later than others, although there are a number of possible factors.

Genes

Research has found that two genes present at birth, known as GPR54 and KiSS1, are responsible for the onset of puberty.

The GPR54 lies dormant (inactive) for many years until it's suddenly activated by special chemicals called kisspeptins that are produced by the KiSS1 gene.

The process of puberty starts when kisspeptins turn on the GPR54 gene, sending signals to your brain and triggering a chain reaction in your body.

An area of the brain known as the hypothalamus activates a hormone called gonadotropin-releasing hormone (GnRH). GnRH sends a signal 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  responsible for changes that occur during puberty.

In boys, testosterone is produced by the testes (male sex organs). Testosterone stimulates the development of the penis and testes and causes muscle and pubic hair growth. It's 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 the main sex hormone in girls. It's produced by the ovaries and stimulates growth of the breasts and reproductive system, and helps regulate the monthly menstrual cycle (periods).

Boys and men also have oestrodiol in their body. It's produced in small amounts by the brain and testes to help maintain bone density.

Triggers of puberty

It's thought 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's no evidence to show 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 rising trend of obesity in girls could explain why the average age of girls beginning puberty has been falling over recent years. But it's not known why obesity doesn't have the same effect in boys.

There's a lot of uncertainty regarding why certain factors seem to trigger puberty and research in this area is ongoing.

Read more about early or delayed puberty.