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The endocrine system is a control system of Ductless Gland s that secrete chemical messengers called Hormone s that circulate within the body via the Blood stream 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 Gland s such as Salivary Gland s, Sweat Gland s 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 .


PHYSIOLOGY

The endocrine system links the brain to the organs that control body Metabolism , Growth And Development , and Reproduction .

Signal transduction of some hormones with Steroid structure involves nuclear hormone receptor proteins that are a class of Ligand activated proteins that, when bound to specific sequences of DNA serve as on-off switches for Transcription within the cell nucleus. These switches control the development and differentiation of skin, bone and behavioral centers in the brain, as well as the continual regulation of reproductive tissues.

The endocrine system regulates its hormones through Negative Feedback . Increases in hormone activity decrease the production of that hormone. The Immune System and other factors contribute as control factors also, altogether maintaining constant levels of hormones.


ENDOCRINE GLANDS AND THE HORMONES SECRETED


In both sexes















In males only



In females only





ROLE IN DISEASE

Diseases of the endocrine system are common, such as Diabetes Mellitus and Thyroid disease.

Endocrinopathies can occur with any of these. Hypofunction can occur as result of loss of reserve, hyposecretion, Agenesis , atrophy, destruction, etc. Hyperfunction can occur as result of hypersecretion, loss of suppression, tumor, Hyperplasia , etc.

Endocrinopathies are classified as primary, secondary, or tertiary.

Primary is target organ dysfunction and is normally associated with increased or decreased secretory hormones. Secondary is a dysfunction that originates elsewhere like the pituitary gland and is normally associated with increased or decreased production of trophic factors. Tertiary is associated with dysfunction of the hypothalamus and its releasing hormones.


DIFFUSE ENDOCRINE SYSTEM

Organs aren't the sole way for hormones to be sent into the body; there are a host of specific cells which secrete hormones independently. These are called the "diffuse" endocrine system, and include Myocytes in the heart (atria) and Epithelial Cell s in the stomach and small intestines. In fact, if one were to classify ''any'' chemical excretions in the term "hormone," every cell in the human body could be considered a part of the endocrine system.


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