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Hormones and Glands
How tall are you going to get? How does your body stay warm? Why does a boy's voice change when he is 12 or 13?
All these activities are controlled by organs called glands. Your glands keep many body functions running smoothly.
Glands make special chemicals that bring messages to every part of your body. These chemical messengers are called hormones. Glands put hormones into the blood. Then the blood carries hormones to the parts of the body where they work.
The pituitary gland makes a hormone that is carried by the blood to the bones. This hormone makes the long bones of the skeleton grow. It helps you reach your adult size.
The thyroid gland controls how fast you use food and change it into energy. With too much of this hormone, the body releases a lot of energy. The heart speeds up. Body temperature goes up. The person may be nervous and lose weight.
Other glands make sex hormones. These hormones control the development of male and female sex characteristics. In girls, the sex glands are the ovaries. They make breasts develop and hips widen. In boys, the sex glands are the testes. They make the voice deepen and body hair grow.
In girls, changes in sex characteristics happen between 8 and 16 years of age. Boys change between 10 and 18. This time of change is called puberty. It is the stage between childhood and adulthood.
Typical puberty changes in boys are: voice "cracking", shoulders widen, genitals develop and darken, pubic hair begins to grow, increase in body odour, and they grow taller. In girls, typical changes are: breasts developing, hips widen, grow taller, and menstrual cycle begins. There are many other signs of puberty but these are most common.