Editing Gender identity (section)

====Transgender and transsexuality====
{{anchor|Biological causes of transgender and transsexuality}}
{{See also|Causes of transsexuality}}

Some studies have investigated whether there is a link between biological variables and [[transgender]] or [[transsexual]] identity.<ref>{{cite journal | vauthors = Vilain E | title = Genetics of intersexuality. | journal = Journal of Gay & Lesbian Psychotherapy | date = July 2006 | volume = 10 | issue = 2 | pages = 9–26 | doi = 10.1300/J236v10n02_02 | s2cid = 142998821 }}</ref><ref name="pmid15617542">{{cite journal | vauthors = Fleming A, Vilain E | title = The endless quest for sex determination genes | journal = Clinical Genetics | volume = 67 | issue = 1 | pages = 15–25 | date = January 2005 | pmid = 15617542 | doi = 10.1111/j.1399-0004.2004.00376.x | s2cid = 7595544 }}</ref><ref>{{cite journal | vauthors = Savic I, Arver S | title = Sex dimorphism of the brain in male-to-female transsexuals | journal = Cerebral Cortex | volume = 21 | issue = 11 | pages = 2525–2533 | date = November 2011 | pmid = 21467211 | doi = 10.1093/cercor/bhr032 | doi-access = free }} Concluded that gynephilic trans women had brains like men's, but in a few areas, trans women's brains were different from both men's and women's brains.</ref> Several studies have shown that [[Sexual dimorphism|sexually dimorphic]] brain structures in transsexuals are shifted away from what is associated with their birth sex and towards what is associated with their preferred sex.<ref>{{cite journal | vauthors = Gizewski ER, Krause E, Schlamann M, Happich F, Ladd ME, Forsting M, Senf W | title = Specific cerebral activation due to visual erotic stimuli in male-to-female transsexuals compared with male and female controls: an fMRI study | journal = The Journal of Sexual Medicine | volume = 6 | issue = 2 | pages = 440–448 | date = February 2009 | pmid = 18761592 | doi = 10.1111/j.1743-6109.2008.00981.x }} Found that a sample of androphilic trans women was shifted towards the female direction in brain responses.</ref><ref>{{cite journal | vauthors = Rametti G, Carrillo B, Gómez-Gil E, Junque C, Segovia S, Gomez Á, Guillamon A | title = White matter microstructure in female to male transsexuals before cross-sex hormonal treatment. A diffusion tensor imaging study | journal = Journal of Psychiatric Research | volume = 45 | issue = 2 | pages = 199–204 | date = February 2011 | pmid = 20562024 | doi = 10.1016/j.jpsychires.2010.05.006 }} Found that the white matter pattern in gynephilic trans men was shifted in the direction of biological males even before the female-to-male transsexuals started taking male hormones.</ref> The volume of the central subdivision of the [[stria terminalis#Bed nucleus of the stria terminalis|bed nucleus of a stria terminalis]] or BSTc (a constituent of the [[basal ganglia]] of the brain which is affected by [[Prenatal androgen transfer|prenatal androgens]]) of transsexual women has been suggested to be similar to women's and unlike men's,<ref>{{cite book | vauthors = Carlsson NR |title=Psychology: The Science of Behavior |date=2010 |publisher=Allyn & Bacon |location=Boston |isbn=978-0-205-54786-9 |edition=7th | page =418 }}</ref><ref>{{cite journal | vauthors = Zhou JN, Hofman MA, Gooren LJ, Swaab DF | title = A sex difference in the human brain and its relation to transsexuality | journal = Nature | volume = 378 | issue = 6552 | pages = 68–70 | date = November 1995 | pmid = 7477289 | doi = 10.1038/378068a0 | bibcode = 1995Natur.378...68Z | hdl-access = free | type = Submitted manuscript | s2cid = 4344570 | hdl = 20.500.11755/9da6a0a1-f622-44f3-ac4f-fec297a7c6c2 | url = https://pure.knaw.nl/portal/en/publications/a-sex-difference-in-the-human-brain-and-its-relation-to-transsexuality(9da6a0a1-f622-44f3-ac4f-fec297a7c6c2).html | access-date = 6 September 2018 | archive-date = 29 August 2017 | archive-url = https://web.archive.org/web/20170829164452/https://pure.knaw.nl/portal/en/publications/a-sex-difference-in-the-human-brain-and-its-relation-to-transsexuality(9da6a0a1-f622-44f3-ac4f-fec297a7c6c2).html | url-status = live }}</ref> but the relationship between BSTc volume and gender identity is still unclear.<ref>{{cite journal | vauthors = Rosenthal SM | title = Approach to the patient: transgender youth: endocrine considerations | journal = The Journal of Clinical Endocrinology and Metabolism | volume = 99 | issue = 12 | pages = 4379–4389 | date = December 2014 | pmid = 25140398 | doi = 10.1210/jc.2014-1919 | quote = the sexually dimorphic differentiation of the BSTc in humans is not present until puberty, in contrast to rats, where such differences in the BST occur in the early postnatal period and apparently require perinatal differences in T levels (44, 45). Given that many transgender adolescents experience significant gender dysphoria before puberty (and before sex differences in BSTc volume emerge), the relationship between BSTc volume and gender identity would appear to be unclear. | doi-access = free }}</ref> Similar [[Biology and sexual orientation#Studies of brain structure|brain structure differences]] have been noted between gay and heterosexual men, and between lesbian and heterosexual women.<ref name="LeVay 1991">{{cite journal | vauthors = LeVay S | title = A difference in hypothalamic structure between heterosexual and homosexual men | journal = Science | volume = 253 | issue = 5023 | pages = 1034–1037 | date = August 1991 | pmid = 1887219 | doi = 10.1126/science.1887219 | bibcode = 1991Sci...253.1034L | s2cid = 1674111 }}</ref><ref name="Byne 2001">{{cite journal | vauthors = Byne W, Tobet S, Mattiace LA, Lasco MS, Kemether E, Edgar MA, Morgello S, Buchsbaum MS, Jones LB | display-authors = 6 | title = The interstitial nuclei of the human anterior hypothalamus: an investigation of variation with sex, sexual orientation, and HIV status | journal = Hormones and Behavior | volume = 40 | issue = 2 | pages = 86–92 | date = September 2001 | pmid = 11534967 | doi = 10.1006/hbeh.2001.1680 | s2cid = 3175414 }}</ref> Transsexuality has a genetic component.<ref>{{cite book | last1= Klink | first1= Daniel | title= Gender Dysphoria and Disorders of Sex Development |date=2013 | chapter=Genetic Aspects of Gender Identity Development and Gender Dysphoria | series= Focus on Sexuality Research |pages=25–51 |chapter-url=https://rdcu.be/dkOSo |publisher=Springer| doi= 10.1007/978-1-4614-7441-8_2 | isbn= 978-1-4614-7440-1 }}</ref>

Research suggests that the same hormones that promote the differentiation of sex organs in utero also elicit puberty and influence the development of gender identity. Different amounts of these male or female sex hormones can result in behavior and external genitalia that do not match the norm of their sex assigned at birth, and in acting and looking like their identified gender.<ref name="Oswalt">{{cite web| vauthors = Oswalt A |title=Factors Influencing Gender Identity|url=http://www.sevencounties.org/poc/view_doc.php?type=doc&id=37697&cn=1272|url-status=dead|archive-url=https://web.archive.org/web/20101218130452/https://sevencounties.org/poc/view_doc.php?type=doc&id=37697&cn=1272|archive-date=18 December 2010|access-date=29 October 2012|publisher=Seven Countries Services, Inc.}}</ref>