The endocrine system is a control system of ductless glands that secrete chemical messengers called hormones that circulate within the body via the bloodstream to affect distant organs. Hormones act as "messengers," and are carried by the bloodstream to different cells in the body, which interpret these messages and act on them. The endocrine system does not include exocrine glands such as salivary glands, sweat glands and glands within the gastrointestinal tract.
The field of medicine that deals with disorders of endocrine glands is endocrinology, a branch of the wider field of internal medicine.

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