Editing Steroid (section)

== Structure ==
The steroid nucleus ([[parent structure|core structure]]) is called [[gonane]] (cyclopentanoperhydrophenanthrene).<ref name="pmid36677830">{{cite journal | vauthors = Yang Y, Krin A, Cai X, Poopari MR, Zhang Y, Cheeseman JR, Xu Y | title = Conformations of Steroid Hormones: Infrared and Vibrational Circular Dichroism Spectroscopy | journal = Molecules | volume = 28 | issue = 2 | pages = 771 | date = January 2023 | pmid = 36677830 | pmc = 9864676 | doi = 10.3390/molecules28020771 | doi-access = free }}</ref> It is typically composed of seventeen [[carbon]] atoms, bonded in four fused rings: three six-member [[cyclohexane]] rings (rings A, B and C in the first illustration) and one five-member [[cyclopentane]] ring (the D ring). Steroids vary by the [[functional groups]] attached to this four-ring core and by the [[oxidation state]] of the rings. [[Sterol]]s are forms of steroids with a [[hydroxy group]] at position three and a skeleton derived from [[cholestane]].<ref name = "IUPAC_steroids">{{cite journal | journal = [[Pure and Applied Chemistry|Pure Appl. Chem.]] | volume = 61 | issue = 10 | pages = 1783–1822 | year = 1989 | title = Nomenclature of steroids, recommendations 1989 | vauthors = Moss GP, ((the Working Party of the IUPAC-IUB Joint Commission on Biochemical Nomenclature)) | doi = 10.1351/pac198961101783 | s2cid = 97612891 | url = http://iupac.org/publications/pac/pdf/1989/pdf/6110x1783.pdf | access-date = 21 February 2012 | archive-date = 30 November 2012 | archive-url = https://web.archive.org/web/20121130182412/http://iupac.org/publications/pac/pdf/1989/pdf/6110x1783.pdf | url-status = live }} ''Also available with the same authors at'' {{cite journal | vauthors =  | title = IUPAC-IUB Joint Commission on Biochemical Nomenclature (JCBN). The nomenclature of steroids. Recommendations 1989 | journal = European Journal of Biochemistry | volume = 186 | issue = 3 | pages = 429–458 | date = December 1989 | pmid = 2606099 | doi = 10.1111/j.1432-1033.1989.tb15228.x | author-link3 = Josef Fried }}; ''Also available online at'' {{cite web|url= http://www.chem.qmul.ac.uk/iupac/steroid/3S01.html|title= The Nomenclature of Steroids|publisher= Queen Mary University of London|location= London, GBR|page= 3S-1.4|access-date= 10 May 2014|archive-date= 10 September 2017|archive-url= https://web.archive.org/web/20170910193822/http://www.chem.qmul.ac.uk/iupac/steroid/3S01.html|url-status= live}}</ref>{{rp|1785f}}<ref name="Hill-1991">Also available in print at {{cite book | vauthors = Hill RA, Makin HL, Kirk DN, Murphy GM | year= 1991 |title= Dictionary of Steroids |url= https://books.google.com/books?isbn=0-412-27060-9 |location= London, GBR |publisher= Chapman and Hall |pages= xxx–lix |isbn= 978-0-412-27060-4 |access-date= 20 June 2015}}</ref> Steroids can also be more radically modified, such as by changes to the ring structure, for example, [[Bond cleavage|cutting]] one of the rings. Cutting Ring B produces [[secosteroid]]s one of which is [[vitamin D3|vitamin D<sub>3</sub>]].

{{multiple image
 | footer = 5α-dihydroprogesterone (5α-DHP), a steroid. The shape of the four rings of most steroids is illustrated (carbon atoms in black, oxygens in red and hydrogens in grey). The [[nonpolar]] "slab" of [[hydrocarbon]] in the middle (grey, black) and the [[ketone|polar]] groups at opposing ends (red) are common features of natural steroids. [[5α-Dihydroprogesterone|5α-DHP]] is an endogenous [[steroid hormone]] and a [[biosynthesis|biosynthetic]] intermediate.
 | image1 = 5alpha-Dihydroprogesterone 3D spacefill.png
 | alt1 = Filled-in diagram of a steroid
 | caption1 = Space-filling representation
 | image2 = 5alpha-Dihydroprogesterone 3D ball.png
 | alt2 = Ball-and-stick diagram of the same steroid
 | caption2 = Ball-and-stick representation
}}