The Endocrine Physiology

The function of the endocrine system is to coordinate and integrate cellular activity within the whole body by regulating cellular and organ function throughout life and maintaining homeostasis. Homeostasis, or the maintenance of a constant internal environment, is critical to ensuring appropriate cellular function. In the classic description of the endocrine system, a chemical messenger or hormone produced by an organ is released into the circulation to produce an effect on a distant target organ. Currently, the definition of the endocrine system is that of an integrated network of multiple organs derived from different embryologic origins that release hormones ranging from small peptides to glycoproteins, which exert their effects either in neighboring or distant target cells. This endocrine network of organs and mediators does not work in isolation and is closely integrated with the central and peripheral nervous systems as well as with the immune systems, leading to currently used terminology such as “neuroendocrine” or “neuroendocrine-immune” systems for describing their interactions. Three basic components make up the core of the endocrine system.