Hormonessecreted from glands in the endocrine system transmit important messages toevery cell in the body through the blood. Nerves react within seconds, buttheir effects soon fade. However, the effects of hormones are longer and canlast for hours, days or even weeks. Endocrine glands are located in differentparts of the body. However, it has a functional integrity and is in closerelationship with the nervous system and works in a coordinated manner. Becauseof this integrity, these processes are evaluated under the name of theendocrine system.

The body,which has to adapt to the changes in the external environment and maintain itsown balance, must have a proper functioning of the endocrine system in order tocope with this situation. This system regulates many functions related tometabolism such as nutrition, salt-fluid balance, reproduction, growth anddevelopment.

 Hormones only affect target cells and arecontrolled in two ways; chemical and neurological control. While the chemicalcontrol of the endocrine system is provided according to the changing bloodhormone order, the neurological control is provided according to the stimulicoming from the central and autonomic nervous system.