Editing Steroid (section)

== Types ==
===By function===
{{expand section|A more detailed explanation of function would also be beneficial|date=January 2019|small=yes}}
The major classes of [[steroid hormones]], with prominent members and examples of related functions, are:<ref name="pmid24940130">{{cite journal |vauthors=Ericson-Neilsen W, Kaye AD |title=Steroids: pharmacology, complications, and practice delivery issues |journal=Ochsner J |volume=14 |issue=2 |pages=203–7 |date=2014 |pmid=24940130 |pmc=4052587}}</ref><ref>{{cite web | url=https://www.mdpi.com/journal/ijms/special_issues/steroid_hormones_sex | title=International Journal of Molecular Sciences | access-date=12 February 2024 | archive-date=12 February 2024 | archive-url=https://web.archive.org/web/20240212192445/https://www.mdpi.com/journal/ijms/special_issues/steroid_hormones_sex | url-status=live }}</ref>
* [[Corticosteroid]]s:
** [[Glucocorticoid]]s:
*** [[Cortisol]], a [[glucocorticoid]] whose functions include [[immunosuppression]]
** [[Mineralocorticoid]]s:
*** [[Aldosterone]], a [[mineralocorticoid]] that helps regulate [[blood pressure]] through water and electrolyte balance
* [[Sex steroid]]s:
** [[Progestogen]]s:
*** [[Progesterone]], which regulates cyclical changes in the [[endometrium]] of the [[uterus]] and maintains a [[pregnancy]]
** [[Androgens]]:
*** [[Testosterone]], which contributes to the development and maintenance of male [[secondary sex characteristic]]s
** [[Estrogens]]:
*** [[Estradiol]], which contributes to the development and maintenance of female secondary sex characteristics

Additional classes of steroids include:
* [[Neurosteroid]]s such as {{abbrlink|DHEA|dehydroepiandrosterone}} and [[allopregnanolone]]
* [[Bile acid]]s such as [[taurocholic acid]]
* [[Aminosteroid]] [[neuromuscular blocking agent]]s (mainly synthetic) such as [[pancuronium bromide]]
* [[Steroidal antiandrogen]]s (mainly synthetic) such as [[cyproterone acetate]]
* [[Steroidogenesis inhibitor]]s (mainly exogenous) such as [[alfatradiol]]
* Membrane sterols such as [[cholesterol]], [[ergosterol]], and various [[phytosterol]]s
* Toxins such as steroidal [[saponin]]s and [[cardenolide]]s/[[cardiac glycoside]]s

As well as the following class of [[secosteroid]]s (open-ring steroids):
* [[Vitamin D]] forms such as [[ergocalciferol]], [[cholecalciferol]], and [[calcitriol]]

=== By structure ===
==== Intact ring system ====
Steroids can be classified based on their chemical composition.<ref name="Zorea-2014">{{cite book|title=Steroids (Health and Medical Issues Today)| vauthors = Zorea A |publisher=Greenwood Press|year=2014|isbn=978-1-4408-0299-7|location=Westport, CT|pages=10–12}}</ref> One example of how [[Medical Subject Headings|MeSH]] performs this classification is available at the Wikipedia MeSH catalog. Examples of this classification include:
[[Image:Cholecalciferol.svg|thumb|alt=Chemical diagram|class=skin-invert-image|[[Cholecalciferol]] (vitamin D{{ssub|3}}), an example of a 9,10-[[secosteroid]]]]
[[Image:Cyclopamine.svg|thumb|alt=Chemical diagram|class=skin-invert-image|[[Cyclopamine]], an example of a complex C-nor-D-homosteroid]]
{| class="wikitable"
|-
! align="center" | Class
! align="center" | Example
! align="center" | Number of carbon atoms
|-
| align="center" | [[Cholestane]]s
| align="center" | Cholesterol
| align="center" | 27
|-
| align="center" | [[Cholane]]s
| align="center" | Cholic acid
| align="center" | 24
|-
| align="center" | [[Pregnane]]s
| align="center" | Progesterone
| align="center" | 21
|-
| align="center" | [[Androstane]]s
| align="center" | Testosterone
| align="center" | 19
|-
| align="center" | [[Estrane]]s
| align="center" | Estradiol
| align="center" | 18
|-
|}
In biology, it is common to name the above steroid classes by the number of carbon atoms present when referring to hormones: C<sub>18</sub>-steroids for the estranes (mostly estrogens), C<sub>19</sub>-steroids for the androstanes (mostly androgens), and C<sub>21</sub>-steroids for the pregnanes (mostly corticosteroids).<ref name="rgd.mcw.edu-C19">{{cite web |title=C19-steroid hormone biosynthetic pathway – Ontology Browser – Rat Genome Database |url=https://rgd.mcw.edu/rgdweb/ontology/view.html?acc_id=PW:0000770 |website=rgd.mcw.edu |access-date=11 April 2022 |archive-date=12 May 2023 |archive-url=https://web.archive.org/web/20230512220253/https://rgd.mcw.edu/rgdweb/ontology/view.html?acc_id=PW:0000770 |url-status=live }}</ref> The classification "[[17-ketosteroid]]" is also important in medicine.

The gonane (steroid nucleus) is the parent 17-carbon tetracyclic hydrocarbon molecule with no [[alkyl]] sidechains.<ref name="pmid10715364">{{cite journal | vauthors = Edgren RA, Stanczyk FZ | title = Nomenclature of the gonane progestins | journal = Contraception | volume = 60 | issue = 6 | pages = 313 | date = Dec 1999 | pmid = 10715364 | doi = 10.1016/S0010-7824(99)00101-8 }}</ref>

==== Cleaved, contracted, and expanded rings ====
Secosteroids (Latin ''seco'', "to cut") are a subclass of steroidal compounds resulting, [[Biosynthesis|biosynthetically]] or conceptually, from scission (cleavage) of parent steroid rings (generally one of the four). Major secosteroid subclasses are defined by the steroid carbon atoms where this scission has taken place. For instance, the prototypical secosteroid [[cholecalciferol]], [[vitamin D3|vitamin D<sub>3</sub>]] (shown), is in the 9,10-secosteroid subclass and derives from the cleavage of carbon atoms C-9 and C-10 of the steroid B-ring; 5,6-secosteroids and 13,14-steroids are similar.<ref name="pmid20424788">{{cite journal | vauthors = Hanson JR | title = Steroids: partial synthesis in medicinal chemistry | journal = Natural Product Reports | volume = 27 | issue = 6 | pages = 887–99 | date = Jun 2010 | pmid = 20424788 | doi = 10.1039/c001262a }}</ref>

[[Norsteroid]]s ([[nor-]], L. ''norma''; "normal" in chemistry, indicating carbon removal)<ref name=iupacRF41>{{cite web | publisher = International Union of Pure and Applied Chemistry (IUPAC) | year = 1999 | title = IUPAC Recommendations: Skeletal Modification in Revised Section F: Natural Products and Related Compounds (IUPAC Recommendations 1999) | url = http://www.chem.qmul.ac.uk/iupac/sectionF/RF41.html#41 | access-date = 20 May 2014 | archive-date = 4 March 2016 | archive-url = https://web.archive.org/web/20160304041709/http://www.chem.qmul.ac.uk/iupac/sectionF/RF41.html#41 | url-status = live }}</ref> and homosteroids (homo-, Greek ''homos''; "same", indicating carbon addition) are structural subclasses of steroids formed from biosynthetic steps. The former involves enzymic [[ring expansion|ring expansion-contraction]] reactions, and the latter is accomplished ([[biomimetic synthesis|biomimetically]]) or (more frequently) through [[ring closure]]s of [[open-chain compound|acyclic]] precursors with more (or fewer) ring atoms than the parent steroid framework.<ref name=Wolfing07>{{cite journal | vauthors = Wolfing J | date = 2007 | title = Recent developments in the isolation and synthesis of D-homosteroids and related compounds | journal = Arkivoc | volume = 2007 | issue = 5 | pages = 210–230 | doi = 10.3998/ark.5550190.0008.517 | url = http://www.arkat-usa.org/get-file/19924/ | doi-access = free | hdl = 2027/spo.5550190.0008.517 | hdl-access = free | access-date = 20 May 2014 | archive-date = 1 February 2013 | archive-url = https://web.archive.org/web/20130201091834/http://www.arkat-usa.org/get-file/19924/ | url-status = live }}</ref>

Combinations of these ring alterations are known in nature. For instance, [[Sheep|ewes]] who graze on [[Veratrum|corn lily]] ingest [[cyclopamine]] (shown) and [[veratramine]], two of a sub-family of steroids where the C- and D-rings are contracted and expanded respectively via a [[biosynthesis|biosynthetic]] migration of the original C-13 atom. Ingestion of these C-nor-D-homosteroids results in birth defects in lambs: [[cyclopia]] from [[cyclopamine]] and leg deformity from veratramine.<ref name=GaoChen2012>{{cite book | veditors = Corey EJ, Li JJ | title = Total synthesis of natural products: at the frontiers of organic chemistry | vauthors = Gao G, Chen C | chapter = Nakiterpiosin | chapter-url = https://books.google.com/books?id=UT5EAAAAQBAJ | doi = 10.1007/978-3-642-34065-9 | date = 2012 | publisher = Springer | location = Berlin | isbn = 978-3-642-34064-2 | s2cid = 92690863 }}</ref> A further C-nor-D-homosteroid (nakiterpiosin) is excreted by [[Okinawa Prefecture|Okinawa]]n [[cyanobacteria|cyanobacteriosponges]]. e.g., ''[[Terpios]] hoshinota'', leading to coral mortality from black coral disease.<ref name="Uemura-2009">{{cite journal | vauthors = Uemura E, Kita M, Arimoto H, Kitamura M | date = 2009 | title = Recent aspects of chemical ecology: Natural toxins, coral communities, and symbiotic relationships | journal = Pure Appl. Chem. | volume = 81 | issue = 6 | pages = 1093–1111 | doi = 10.1351/PAC-CON-08-08-12| doi-access = free }}</ref> Nakiterpiosin-type steroids are active against the signaling pathway involving the [[smoothened]] and [[hedgehog (cell signaling)|hedgehog]] proteins, a pathway which is hyperactive in a number of cancers.{{citation needed|date=March 2019}}