Editing Endocrine system (section)

===Hormones===
{{Main|Hormone}}
A [[hormone]] is any of a class of [[cell signalling|signaling molecules]] produced by cells in [[gland]]s in [[multicellular organism]]s that are transported by the [[circulatory system]] to target distant organs to regulate [[physiology]] and [[behaviour]]. Hormones have diverse chemical structures, mainly of 3 classes: [[eicosanoid]]s, [[steroid]]s, and [[amino acid]]/[[protein]] derivatives ([[amine]]s, [[peptide]]s, and [[protein]]s). The glands that secrete hormones comprise the endocrine system. The term hormone is sometimes extended to include chemicals produced by cells that affect the same cell ([[autocrine signaling|autocrine]] or [[intracrine|intracrine signalling]]) or nearby cells ([[paracrine signalling]]).

Hormones are used to communicate between [[organ (anatomy)|organs]] and tissues for [[physiological]] regulation and [[behavioral]] activities, such as digestion, [[metabolism]], [[respiration (physiology)|respiration]], [[tissue (biology)|tissue]] function, [[sensory perception]], [[sleep]], [[excretion]], [[lactation]], [[Stress (physiology)|stress]], [[human development (biology)|growth and development]], [[Motor coordination|movement]], [[reproduction]], and [[mood (psychology)|mood]].<ref>{{cite book |author=Neave N |title=Hormones and behaviour: a psychological approach |year=2008 |publisher=Cambridge Univ. Press |location=Cambridge |isbn=978-0-521-69201-4}}
* {{cite journal |author=Claire L. Gibson |title=Hormones and Behaviour: A Psychological Approach |journal=Perspectives in Biology and Medicine |type=Review |volume=53 |issue=1 |pages=152–155 |date=Winter 2010 |doi=10.1353/pbm.0.0141 |s2cid=72100830 |url=http://muse.jhu.edu/journals/pbm/summary/v053/53.1.gibson.html|url-access=subscription }}</ref><ref>{{cite web |title=Hormones |url=https://www.nlm.nih.gov/medlineplus/hormones.html |website=MedlinePlus |publisher=U.S. National Library of Medicine}}</ref>

Hormones affect distant cells by binding to specific [[receptor (biochemistry)|receptor]] proteins in the target cell resulting in a change in cell function. This may lead to cell type-specific responses that include rapid changes to the activity of existing proteins, or slower changes in the [[gene expression|expression]] of target genes. Amino acid–based hormones ([[amines]] and [[peptide hormone|peptide or protein hormones]]) are water-soluble and act on the surface of target cells via [[signal transduction]] pathways; [[steroid hormone]]s, being lipid-soluble, move through the [[plasma membrane]]s of target cells to act within their [[cell nucleus|nuclei]].