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Endocrine glands release hormones directly into the circulatory system that have specific actions at sites remote to the site of secretion. A signaling cell sends a signaling molecule (cytokine, chemokine, etc) that binds to a receptor on the target cell. The main signaling molecules of endocrine glands are hormones.

 Three types of cellular communication via chemical compounds

Autocrine Same cell
Paracrine Nearby cells via tissue fluid
Endocrine Distant cells via circulation

 Two Types of Glands

Exocrine Secretion through a duct
Endocrine Ductless glands

* Please note that the pancreas is both an endocrine and exocrine gland.

 Cell signaling can lead to:

  1. Gene activation
  2. Growth factor synthesis
  3. Receptor synthesis

 You know a substance is a hormone / endocrine gland if:

  1. Removal of the gland produces abnormal symptoms
  2. Symptoms are alleviated when gland or extract of the gland is returned to the organism
  3. Administered hormone (natural or synthetic) relieves symptoms

Four main functions of hormones are:

  1. Control of reproduction
  2. Regulation of growth and development
  3. Maintain internal environment (homeostasis)
  4. Regulate energy production, utilization, and storage

Three Types of Hormones Secreted By Endocrine Glands




Peptides Insulin (cannot be taken orally)
Amines Dopamine
Steroids Estrogen

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Last updated October 2013