Steroid
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{{about|the chemical family of steroids|the performance enhancing substance|Anabolic steroid}}
[[Image:Lanosterol-skeletal.png|thumb|right|250px|Steroid skeleton of [[lanosterol]]. The total number of carbons (30) reflects its [[triterpenoid]] origin.]]
A '''steroid''' is a [[terpenoid]] [[lipid]] characterized by a [[carbon]] skeleton with four fused rings, generally arranged in a 6-6-6-5 fashion.
Steroids vary by the [[functional group]]s attached to these rings and the [[oxidation]] state of the rings. Hundreds of distinct steroids are found in [[plant]]s, [[animal]]s, and [[Fungus|fungi]]. All steroids are made in cells either from the [[sterol]] [[lanosterol]] (animals and fungi) or the sterol [[cycloartenol]] (plants). Both sterols are derived from the cyclization of the [[triterpene]] [[squalene]].<ref>[http://www.chem.qmul.ac.uk/iubmb/enzyme/reaction/terp/lanost.html Lanosterol biosynthesis<!-- Bot generated title -->]</ref>
==Origin==
[[Image:Sterol synthesis.svg|thumb|right|350px|Simplified version of the steroid synthesis pathway with the intermediates [[isopentenyl pyrophosphate]] (IPP), [[dimethylallyl pyrophosphate]] (DMAPP), [[geranyl pyrophosphate]] (GPP) and [[squalene]] shown. Some intermediates are omitted.]]
Steroids include [[estrogen]] (US spelling) or oestrogen (UK/AUS spelling), [[progesterone]] and [[testosterone]]. Estrogen and progesterone are made primarily in the [[ovary]] and in the [[placenta]] during pregnancy and [[testosterone]] in the [[testes]]. Testosterone is also converted into estrogen to regulate the supply of each, in the bodies of both females and males. Certain [[neurons]] and [[glia]] in the [[central nervous system]] (CNS) express the [[enzymes]] that are required for the local synthesis of [[pregnane]] [[neurosteroids]], either [[de novo synthesis|''de novo'']] or from peripherally derived sources. The rate limiting step of steroid synthesis is the conversion of [[cholesterol]] to [[pregnenolone]] which occurs inside the [[mitochondrion]].<ref name=Rossier>{{cite journal | title=T channels and steroid biosynthesis: in search of a link with mitochondria | author=Rossier MF | journal=Cell Calcium. | date=2006 | volume=40 | issue=2 | pages=155–64 | pmid=16759697 | doi=10.1016/j.ceca.2006.04.020 }}</ref>
==Classification==
===Taxonomical/Functional===
Some of the common categories of steroids:
*Animal steroids
**[[Insect]] steroids
***Ecdysteroids such as [[ecdysterone]]
**[[Vertebrate]] steroids
***[[Steroid hormone]]s
****[[Sex steroid]]s are a subset of [[sex hormone]]s that produce [[sexual differentiation|sex differences]] or support [[reproduction]]. They include [[androgen]]s, [[estrogen]]s, and [[progestagen]]s.
****[[Corticosteroid]]s include [[glucocorticoid]]s and [[mineralocorticoid]]s. [[Glucocorticoid]]s regulate many aspects of [[metabolism]] and [[immune system|immune function]], whereas [[mineralocorticoid]]s help maintain blood volume and control [[kidney|renal]] excretion of [[electrolyte]]s.
****[[Anabolic steroid]]s are a class of steroids that interact with androgen receptors to increase muscle and bone synthesis. There are natural and synthetic anabolic steroids. In popular language the word "steroids" usually refers to anabolic steroids.
***[[Cholesterol]] which modulates the fluidity of [[cell membranes]] and is the principle constituent of the plaques implicated in [[atherosclerosis]].
*Plant steroids
**[[Phytosterol]]s
**[[Brassinosteroid]]s
*Fungus steroids
**[[Ergosterol]]s
===Structural===
It is also possible to classify steroids based upon their chemical composition. One example of how [[MeSH]] performs this classification is available at [[Wikipedia:MeSH D04#MeSH D04.808 --- steroids|the Wikipedia MeSH catalog]]. Examples from this classification include:
{| class="wikitable"
|-
! align="center" | Class
! align="center" | Examples
! align="center" | Number of carbon atoms
|-
| align="center" | Cholstanes
| align="center" | [[cholesterol]]
| align="center" | 27
|-
| align="center" | Cholanes
| align="center" | [[cholic acid]]
| align="center" | 22
|-
| align="center" | Pregnanes
| align="center" | [[progesterone]]
| align="center" | 21
|-
| align="center" | Androstanes
| align="center" | [[testosterone]]
| align="center" | 19
|-
| align="center" | Estranes
| align="center" | [[estradiol]]
| align="center" | 18
|-
|}
==See also==
*[[Batrachotoxin]]
*[[List of steroid abbreviations]]
*[[Steroid biosynthesis]]
==References==
{{reflist}}
==Further reading==
* {{cite journal | journal = [[Pure & Appl. Chem.]] | volume = 61 | issue = 10 | pages = 1783–1822 | year = 1989 | title = Nomenclature of Steroids (Recommendations 1989) | author = G. P. Moss | url = http://www.iupac.org/publications/pac/1989/pdf/6110x1783.pdf | doi = 10.1351/pac198961101783}}
== External links ==
* [http://www.indstate.edu/thcme/mwking/steroid-hormones.html Michael W. King's Medical Biochemistry]. Steroids and retinoids are both [[terpene]]s which are [[hydrophobic]], pass through [[cell membrane]]s and bind to [[Signal transduction# Nuclear receptors|intracellular receptors]]. However, retinoic acid is not a steroid because it does not have the defining ring structure. See: [http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Search&db=books&doptcmdl=GenBookHL&term=retinoids+AND+stryer%5Bbook%5D+AND+217301%5Buid%5D&rid=stryer.section.4466#4467 Steroids and Related Hydrophobic Molecules].
* "[http://www.ncbi.nlm.nih.gov/books/bv.fcgi?call=bv.View..ShowTOC&rid=stryer.TOC&depth=2 Biochemistry]" by Jeremy M. Berg, John L. Tymoczko and Lubert Stryer (2002) W. H. Freeman and Co. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=Books&cmd=Search&term=steroid+AND+stryer%5Bbook%5D&doptcmdl=TOCView steroid topics in this]
*[http://www.insidermedicine.com/Archives/Steroids,_Rage_and_Criminal_Activity_316.aspx Steroids, Rage and Criminal Activity] -- Video: Insidermedicine.com's Maria Radina on Anabolic Androgenic Steroids, as presented in a study in ''Archives of General Psychiatry''.
*[http://www.chem.qmul.ac.uk/iupac/steroid/ Nomenclature of Steroids Home Page] at Queen Mary University of London.
*[http://web.archive.org/web/20061117030358/http://il-st-acad-sci.org/steroid0.html Steroid abbreviations] at ISAS (page now defunct, web archive version)
{{Steroids}}
[[Category:Steroids|*]]
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[[th:สเตอรอยด์]]
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[[zh:類固醇]]