Hormones are substances that are secreted by a group of glands in the body.
This collection of glands is called the endocrine system. The hormones are carried by
the blood to places in the body where they regulate the functions of their "target"
organs. These hormones tell the organs when to operate and regulate their operation
rate. The hormones coordinate body activities, control growth and development, and
maintain homeostasis. When the supplying glands produce too few hormones (or stop
producing), the body functions are always affected. An example of this is the insulin
produced by a part of the pancreas. When the production of this hormone is
insufficient, the body develops the disease we call "diabetes mellitus," an inability to
properly oxidize carbohydrates.