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.

American Medical Association: Endocrine System - Includes a graphic showing the location and function of the endocrine glands in the body.
Meta Description: [ Atlas of the Body -- Endocrine System ]
Endocrine Disrupters - From the Whyfiles, a study by the Environmental Protection Agency about synthetic chemicals causing hormone problems. Includes a look at the effects of pesticides on hormones, an overview of the human endocrine system, how endocrine disrupters work, and the EPA's action plan.
Endocrine System - Features a series of tissue samples from the pituitary, thyroid, and adrenal glands
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Hormones: Sources, Targets and Functions - A table showing endocrine glands, hormones produced by each, and functions.
Introduction to Hormone Disrupting Chemicals - An introduction to the effects of hormone disrupting chemicals on man and the environment, an overview of the endocrine system, and the response of governments and industry to this problem. Includes internet links and other references.
The Hormones of the Human - Table of hormones, diagram of location of endocrine glands, categories and types of hormones, and regulation and transport.
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