We can compare the body's glandular system to a thermostat in any heating system.  When the room termperature falls, the thermostat instructs the central heating system to switch on until the temperature rises.  Then the thermostat switches off so thhe room doesn't get too hot.  In the human body, hormones control conditions in the body so that a steady state is maintained.

The glandular system consists of the pituitary gland, thyroid gland, parathyroid gland, thymus gland, sex glands (ovaries, testes), pancreas, hypothalamus and adrenal glands.  These all work together in monitoring the body's functions and ordering it to make any needed adjustments.  The hypothalamus is the link between the endocrine and nervous systems.

The glands produce and excrete chemical substances known as hormones.  Hormones coordinate and control various organs and tissues so that all parts of the body work together smooothly and efficiently.  Any deviation from normal has to be remedied immediately or life can be threatened.

Hormones (from the Greek word meaning "to stir up") regulate basic drives and emotions, promote growth and sexual identity, control body temperature, asssist in the repair of broken tissue and help generate energy.

The amount of hormones released depends on what the body needs.  Levels change in response to infection, stress and changes in chemical composition of the blood.  There is a constant, fine control in this system.  The hormone that controls water excretion, for example, is itself controlled by the amount of water in the body.  Stress can also interfere with the glands and may cause an overproduction of some hormones.