Hormone definition for kids - What are Hormones?

Are you tall for your age, or short?
How tall you grow depends mostly on chemical substances called hormones, which move around your body in your blood.
Some hormones cause the cells in your body to make more protein. They then make the cells grow and divide, so that all of your body gets bigger.
Because hormones are going around in your blood, they reach every cell in your body. So all your cells grow and divide at your normal rate.
Can you imagine how it would be if some-parts of your body grew faster than others? 
This is why hormones are so important.

Hormones control the different parts of your body, so that everything is regulated.
Hormones are regulators of chemical and growth activity in the body.

A special kind of hormone, called growth hormone, helps the long bones to grow. Children who do not produce enough of this hormone may not grow as tall as they would be able to grow with the hormone.

The balance of hormones in your blood is controlled by the pituitary gland, which lies just below the brain.

The pituitary gland produces hormones which control many of the body’s activities.
Large numbers of nerve cells and blood vessels link the pituitary gland to a part of the brain called the hypothalamus. 
The hypothalamus controls the pituitary gland by sending “on” and “off ” messages through the nerve cells and the bloodstream.
These messages affect the pituitary gland with regard to the releasing of its hormones.