Hormone: Difference between revisions

[[File:Hormone Transport.png|thumb|283x283px|Left: A hormone feedback loop in a female adult. (1) [[follicle-stimulating hormone]], (2) [[luteinizing hormone]], (3) [[progesterone]], (4) [[estradiol]]. Right: [[auxin]] transport from leaves to roots in ''[[Arabidopsis thaliana]]'']]

Hormones are used to communicate between [[organ (anatomy)|organs]] and [[Tissue (biology)|tissues]]. In [[vertebrate]]s, hormones are responsible for regulating a wide range of processes including both [[physiological]] processes and [[behavioral]] activities such as [[digestion]], [[metabolism]], [[respiration (physiology)|respiration]], [[sensory perception]], [[sleep]], [[excretion]], [[lactation]], [[stress (physiology)|stress]] induction, [[human development (biology)|growth and development]], [[motor coordination|movement]], [[reproduction]], and [[mood (psychology)|mood]] manipulation.<ref>{{cite book | vauthors = Neave N | title= Hormones and behaviour: a psychological approach | year= 2008 | publisher= Cambridge Univ. Press | location= Cambridge | isbn= 978-0-521-69201-4}}</ref><ref name="Project Muse 2010 pp. 152–155">{{cite journal | title= Hormones and Behaviour: A Psychological Approach (review) | journal=Perspectives in Biology and Medicine | publisher=Project Muse | volume=53 | issue=1 | year=2010 | issn=1529-8795 | doi=10.1353/pbm.0.0141 | pages=152–155 | vauthors = Gibson CL | s2cid=72100830 }}</ref><ref>{{cite web | title= Hormones | url= https://medlineplus.gov/hormones.html | work= MedlinePlus | publisher= U.S. National Library of Medicine}}</ref> In plants, hormones modulate almost all aspects of development, from [[germination]] to [[senescence]].<ref>{{Cite web|title=Hormone - The hormones of plants|url=https://www.britannica.com/science/hormone|access-date=2021-01-05|website=Encyclopedia Britannica|language=en}}</ref>

Hormones affect distant cells by binding to specific [[receptor (biochemistry)|receptor]] proteins in the target cell, resulting in a change in cell function. When a hormone binds to the receptor, it results in the activation of a [[signal transduction]] pathway that typically activates gene [[transcription (genetics)|transcription]], resulting in increased [[gene expression|expression]] of target [[protein]]s. Hormones can also act in non-genomic pathways that synergize with genomic effects.<ref>{{cite journal | vauthors = Ruhs S, Nolze A, Hübschmann R, Grossmann C | title = 30 Years of the Mineralocorticoid Receptor: Nongenomic effects via the mineralocorticoid receptor | journal = The Journal of Endocrinology | volume = 234 | issue = 1 | pages = T107–T124 | date = July 2017 | pmid = 28348113 | doi = 10.1530/JOE-16-0659 | doi-access = free }}</ref> Water-soluble hormones (such as peptides and amines) generally act on the surface of target cells via [[second messenger system|second messengers]]. Lipid soluble hormones, (such as [[steroid]]s) generally pass through the plasma membranes of target cells (both [[cell membrane|cytoplasmic]] and [[nuclear membrane|nuclear]]) to act within their [[cell nucleus|nuclei]]. Brassinosteroids, a type of polyhydroxysteroids, are a sixth class of plant hormones and may be useful as an anticancer drug for endocrine-responsive tumors to cause [[apoptosis]] and limit plant growth. Despite being lipid soluble, they nevertheless attach to their receptor at the cell surface.<ref>{{cite journal | vauthors = Wang ZY, Seto H, Fujioka S, Yoshida S, Chory J | title = BRI1 is a critical component of a plasma-membrane receptor for plant steroids | journal = Nature | volume = 410 | issue = 6826 | pages = 380–3 | date = March 2001 | pmid = 11268216 | doi = 10.1038/35066597 | bibcode = 2001Natur.410..380W | s2cid = 4412000 }}</ref>

In vertebrates, [[endocrine gland]]s are specialized organs that [[Secretion|secrete]] hormones into the [[endocrine system|endocrine signaling system]]. Hormone secretion occurs in response to specific biochemical signals and is often subject to [[Negative feedback|negative feedback regulation]]. For instance, high [[blood sugar]] (serum glucose concentration) promotes [[insulin]] synthesis. Insulin then acts to reduce glucose levels and maintain [[homeostasis]], leading to reduced insulin levels. Upon secretion, water-soluble hormones are readily transported through the circulatory system. Lipid-soluble hormones must bond to [[carrier plasma glycoprotein]]s (e.g., [[thyroxine-binding globulin]] (TBG)) to form [[ligand (biochemistry)|ligand]]-protein complexes. Some hormones, such as insulin and growth hormones, can be released into the bloodstream already fully active. Other hormones, called [[prohormone]]s, must be activated in certain cells through a series of steps that are usually tightly controlled.<ref>{{Cite book| vauthors = Miller BF, Keane CB |title=Miller-Keane Encyclopedia & dictionary of medicine, nursing & allied health.|date=1997|publisher=Saunders |isbn=0-7216-6278-1|edition=6th|location=Philadelphia|oclc=36465055}}</ref> The [[endocrine system]] [[secrete]]s hormones directly into the [[circulatory system|bloodstream]], typically via [[capillary#Types|fenestrated capillaries]], whereas the [[exocrine system]] secretes its hormones indirectly using [[duct (anatomy)|ducts]]. Hormones with [[paracrine]] function diffuse through the [[interstitial fluid|interstitial space]]s to nearby target tissue.

Plants lack specialized organs for the secretion of hormones, although there is spatial distribution of hormone production. For example, the hormone auxin is produced mainly at the tips of young [[Leaf|leaves]] and in the [[Meristem|shoot apical meristem]]. The lack of specialised glands means that the main site of hormone production can change throughout the life of a plant, and the site of production is dependent on the plant's age and environment.<ref>{{Cite web|title=Plant Hormones/Nutrition|url=https://www2.estrellamountain.edu/faculty/farabee/biobk/BioBookPLANTHORM.html#:~:text=They%20are%20produced%20in%20the,lighter%20side%20of%20the%20plant.|access-date=2021-01-07|website=www2.estrellamountain.edu|archive-date=2021-01-09|archive-url=https://web.archive.org/web/20210109180441/https://www2.estrellamountain.edu/faculty/farabee/biobk/BioBookPLANTHORM.html#:~:text=They%20are%20produced%20in%20the,lighter%20side%20of%20the%20plant.|url-status=dead}}</ref>

[[Arnold Adolph Berthold]] was a German [[physiology|physiologist]] and [[zoology|zoologist]], who, in 1849, had a question about the function of the [[testicle|testes]]. He noticed in castrated roosters that they did not have the same sexual behaviors as [[rooster]]s with their testes intact. He decided to run an experiment on male roosters to examine this phenomenon. He kept a group of roosters with their testes intact, and saw that they had normal sized wattles and combs (secondary [[sex organ|sexual organs]]), a normal crow, and normal sexual and aggressive behaviors. He also had a group with their testes surgically removed, and noticed that their secondary sexual organs were decreased in size, had a weak crow, did not have sexual attraction towards females, and were not aggressive. He realized that this organ was essential for these behaviors, but he did not know how. To test this further, he removed one testis and placed it in the abdominal cavity. The roosters acted and had normal physical [[anatomy]]. He was able to see that location of the testes does not matter. He then wanted to see if it was a [[genetics|genetic]] factor that was involved in the testes that provided these functions. He transplanted a testis from another rooster to a rooster with one testis removed, and saw that they had normal behavior and physical anatomy as well. Berthold determined that the location or genetic factors of the testes do not matter in relation to sexual organs and behaviors, but that some [[chemical]] in the testes being secreted is causing this phenomenon. It was later identified that this factor was the hormone [[testosterone]].<ref name="Belfiore_2018">{{cite book |title=Principles of Endocrinology and Hormone Action | vauthors = Belfiore A, LeRoith PE |isbn=978-3-319-44675-2|location=Cham | publisher = Springer |oclc=1021173479|date=2018}}</ref><ref>{{cite book |title=Endocrine Physiology| veditors = Molina PE |date= 2018|publisher= McGraw-Hill Education |isbn=978-1-260-01935-3 |oclc=1034587285}}</ref>

British physician [[George Oliver (physician)|George Oliver]] and physiologist [[Edward Albert Sharpey-Schafer|Edward Albert Schäfer]], professor at University College London, collaborated on the physiological effects of adrenal extracts. They first published their findings in two reports in 1894, a full publication followed in 1895.<ref>{{cite journal | vauthors =  | title = Proceedings of the Physiological Society, March 10, 1894. No. I | journal = The Journal of Physiology | volume = 16 | issue = 3–4 | pages = i-viii | date = April 1894 | pmid = 16992168 | pmc = 1514529 | doi = 10.1113/jphysiol.1894.sp000503 }}</ref><ref>{{cite journal | vauthors = Oliver G, Schäfer EA | title = The Physiological Effects of Extracts of the Suprarenal Capsules | journal = The Journal of Physiology | volume = 18 | issue = 3 | pages = 230–276 | date = July 1895 | pmid = 16992252 | pmc = 1514629 | doi = 10.1113/jphysiol.1895.sp000564 }}</ref> Though frequently falsely attributed to [[secretin]], found in 1902 by Bayliss and Starling, Oliver and Schäfer's adrenal extract containing [[adrenaline]], the substance causing the physiological changes, was the first hormone to be discovered. The term hormone would later be coined by Starling.<ref>{{cite book | vauthors = Bayliss WM, Starling EH | veditors = Leicester HM |chapter=The Mechanism of Pancreatic Secretion |doi=10.4159/harvard.9780674366701.c111 |title=Source Book in Chemistry, 1900–1950 | journal = Canadian Medical Association Journal |publisher=Harvard University Press |isbn=978-0-674-36670-1 |year=1968| volume = 16 | issue = 10 | pages = 311–313 | pmid = 20316002 | pmc = 1709046 }}</ref>

[[William Bayliss]] and [[Ernest Starling]], a [[physiology|physiologist]] and [[biologist]], respectively, wanted to see if the [[nervous system]] had an impact on the [[human digestive system|digestive system]]. They knew that the [[pancreas]] was involved in the secretion of [[digestive fluid]]s after the passage of food from the [[stomach]] to the [[gastrointestinal tract|intestines]], which they believed to be due to the nervous system. They cut the nerves to the pancreas in an animal model and discovered that it was not nerve impulses that controlled secretion from the pancreas. It was determined that a factor secreted from the intestines into the [[bloodstream]] was stimulating the pancreas to secrete digestive fluids. This was named [[secretin]]: a hormone.

Hormonal effects are dependent on where they are released, as they can be released in different manners.<ref name="Molina_2018">{{cite book|title=Endocrine physiology | vauthors = Molina PE |date=2018|publisher=McGraw-Hill Education|isbn=978-1-260-01935-3|oclc=1034587285}}</ref> Not all hormones are released from a cell and into the blood until it binds to a receptor on a target. The major types of hormone signaling are:

|+Signaling Types - Hormones

|Proteins/

|[[Amino acid]] hormones are derived from amino acids, most commonly [[Tyrosine]]. They are stored in vesicles. Examples include [[Melatonin]] and [[Thyroxine]].

Compared with vertebrates, [[insect]]s and [[crustacean]]s possess a number of structurally unusual hormones such as the [[juvenile hormone]], a [[sesquiterpenoid]].<ref name="pmid15612033">{{cite journal | vauthors = Heyland A, Hodin J, Reitzel AM | title = Hormone signaling in evolution and development: a non-model system approach | journal = BioEssays | volume = 27 | issue = 1 | pages = 64–75 | date = January 2005 | pmid = 15612033 | doi = 10.1002/bies.20136 }}</ref>

Not only can hormones influence behavior, but also behavior and the environment can influence hormone concentration.<ref>{{Citation| vauthors = Nelson RJ |title=Hormones and Behavior: Basic Concepts|date=2010|url=https://linkinghub.elsevier.com/retrieve/pii/B9780080453378002369|encyclopedia=Encyclopedia of Animal Behavior|pages=97–105|publisher=Elsevier|language=en|doi=10.1016/b978-0-08-045337-8.00236-9|isbn=978-0-08-045337-8|s2cid=7479319 |access-date=2021-11-18|url-access=subscription}}</ref> Thus, a feedback loop is formed, meaning behavior can affect hormone concentration, which in turn can affect behavior, which in turn can affect hormone concentration, and so on.<ref>{{cite journal | vauthors = Garland T, Zhao M, Saltzman W | title = Hormones and the Evolution of Complex Traits: Insights from Artificial Selection on Behavior | journal = Integrative and Comparative Biology | volume = 56 | issue = 2 | pages = 207–24 | date = August 2016 | pmid = 27252193 | pmc = 5964798 | doi = 10.1093/icb/icw040 }}</ref> For example, hormone-behavior feedback loops are essential in providing constancy to episodic hormone secretion, as the behaviors affected by episodically secreted hormones directly prevent the continuous release of sad hormones.<ref>{{Cite book|title=Principles of hormone/behavior relations|publisher=[[Academic Press]]| vauthors = Pfaff DW, Rubin RT, Schneider JE, Head GA |year=2018|isbn=978-0-12-802667-0|edition=2nd|location=London, United Kingdom|language=en-GB|oclc=1022119040}}</ref>

* Assuming the travel distance is equivalent, neural signals can be transmitted much more quickly (in the range of milliseconds) than can hormonal signals (in the range of seconds, minutes, or hours). Neural signals can be sent at speeds up to 100 meters per second.<ref>{{Cite book|title=Molecular biology of the cell| vauthors = Alberts B, Johnson A, Lewis J, Raff M, Roberts K, Walter P |date=2002|publisher=Garland Science |isbn=0-8153-3218-1|edition=4th|location=New York|oclc=48122761}}</ref>