Editing Digit ratio (section)

===Developmental disorders===
Women with [[congenital adrenal hyperplasia]] (CAH), who have elevated androgen levels before birth, have lower (more masculine) 2D:4D on average<ref name="Brown_2002">{{cite journal | vauthors = Brown WM, Hines M, Fane BA, Breedlove SM | title = Masculinized finger length patterns in human males and females with congenital adrenal hyperplasia | journal = Hormones and Behavior | volume = 42 | issue = 4 | pages = 380–386 | date = December 2002 | pmid = 12488105 | doi = 10.1006/hbeh.2002.1830 | s2cid = 8886238 }}</ref><ref name="Okten_2002">{{cite journal | vauthors = Okten A, Kalyoncu M, Yariş N | title = The ratio of second- and fourth-digit lengths and congenital adrenal hyperplasia due to 21-hydroxylase deficiency | journal = Early Human Development | volume = 70 | issue = 1–2 | pages = 47–54 | date = December 2002 | pmid = 12441204 | doi = 10.1016/s0378-3782(02)00073-7 }}</ref><ref name="Ciumas_2009">{{cite journal | vauthors = Ciumas C, Lindén Hirschberg A, Savic I | title = High fetal testosterone and sexually dimorphic cerebral networks in females | journal = Cerebral Cortex | volume = 19 | issue = 5 | pages = 1167–1174 | date = May 2009 | pmid = 18854582 | doi = 10.1093/cercor/bhn160 | doi-access = free }}</ref> along with other possible physiological effects such as an enlarged [[clitoris]] and shallow [[vagina]].<ref>{{cite book| vauthors = McAnulty RD, Burnette MM |year= 2006| url= https://books.google.com/books?id=KBi9aG0pQAkC&pg=PA165 |title= Sex and sexuality | volume = 1 | publisher= [[Greenwood Publishing Group]]| page= 165| isbn= 9780313049194}}</ref> Males with CAH also express lower digit ratios than [[case–control study|controls]].<ref name="Brown_2002" /><ref name="Okten_2002" /> Amniocentesis samples in males with CAH show that prenatal levels of testosterone are in the high-normal range and levels of the weaker androgen [[androstenedione]] are several fold higher than in controls,<ref name="Pang_1980">{{cite journal | vauthors = Pang S, Levine LS, Cederqvist LL, Fuentes M, Riccardi VM, Holcombe JH, Nitowsky HM, Sachs G, Anderson CE, Duchon MA, Owens R, Merkatz I, New MI | display-authors = 6 | title = Amniotic fluid concentrations of delta 5 and delta 4 steroids in fetuses with congenital adrenal hyperplasia due to 21 hydroxylase deficiency and in anencephalic fetuses | journal = The Journal of Clinical Endocrinology and Metabolism | volume = 51 | issue = 2 | pages = 223–229 | date = August 1980 | pmid = 6447160 | doi = 10.1210/jcem-51-2-223 }}</ref><ref name="Dörr_1993">{{cite journal | vauthors = Dörr HG, Sippell WG | title = Prenatal dexamethasone treatment in pregnancies at risk for congenital adrenal hyperplasia due to 21-hydroxylase deficiency: effect on midgestational amniotic fluid steroid levels | journal = The Journal of Clinical Endocrinology and Metabolism | volume = 76 | issue = 1 | pages = 117–120 | date = January 1993 | doi = 10.1210/jcem.76.1.8421074 | pmid = 8421074 }}</ref><ref name="Wudy_1999">{{cite journal | vauthors = Wudy SA, Dörr HG, Solleder C, Djalali M, Homoki J | title = Profiling steroid hormones in amniotic fluid of midpregnancy by routine stable isotope dilution/gas chromatography-mass spectrometry: reference values and concentrations in fetuses at risk for 21-hydroxylase deficiency | journal = The Journal of Clinical Endocrinology and Metabolism | volume = 84 | issue = 8 | pages = 2724–2728 | date = August 1999 | doi = 10.1210/jcem.84.8.5870 | pmid = 10443667 | doi-access = free }}</ref> indicating that males with CAH are exposed to greater prenatal concentrations of total androgens.

A greater (more feminine) digit ratio occurs for men with [[Klinefelter's syndrome]], who have reduced testosterone secretion throughout life compared to their fathers or to controls.<ref name=Manning_2013/>

Digit ratio in men may correlate with genetic variation in the [[androgen receptor]] gene.<ref name="Manning_2003">{{Cite journal |doi=10.1016/S1090-5138(03)00052-7 |title=The second to fourth digit ratio and variation in the androgen receptor gene |year=2003 |vauthors = Manning JT, Bundred PE, Newton DJ, Flanagan BF |journal=Evolution and Human Behavior |volume=24 |pages=399–405 |issue=6 |bibcode=2003EHumB..24..399M }}</ref> Men with genes that produce androgen receptors that are less sensitive to testosterone (because they have more [[CAG repeats]]) have greater digit ratios, though there have also been reports of failure in replicating this finding.<ref>{{Cite journal| vauthors = Hampson E, Sankar JS |title=Re-examining the Manning hypothesis: androgen receptor polymorphism and the 2D:4D ratio |journal=Evol Hum Behav |volume=33 | issue= 5|pages=557–561 |year=2012 |doi=10.1016/j.evolhumbehav.2012.02.003|bibcode=2012EHumB..33..557H }}</ref> Men with less sensitive androgen receptors may compensate for this by secreting more testosterone via reduced inhibitory feedback on [[gonadotropins]].<ref>{{cite journal | vauthors = Crabbe P, Bogaert V, De Bacquer D, Goemaere S, Zmierczak H, Kaufman JM | title = Part of the interindividual variation in serum testosterone levels in healthy men reflects differences in androgen sensitivity and feedback set point: contribution of the androgen receptor polyglutamine tract polymorphism | journal = The Journal of Clinical Endocrinology and Metabolism | volume = 92 | issue = 9 | pages = 3604–3610 | date = September 2007 | pmid = 17579205 | doi = 10.1210/jc.2007-0117 | s2cid = 33761349 | doi-access = free }}</ref> Thus, it is not clear that 2D:4D would be expected to correlate with CAG repeats, even if it accurately reflects prenatal androgen.

XY individuals with [[androgen insensitivity syndrome]] due to a dysfunctional gene for the androgen receptor present as women and have greater digit ratios on average, as would be predicted if androgenic hormones affect digit ratios. This finding suggests that the sex difference in digit ratios may be unrelated to the [[Y chromosome]] per se.<ref>{{cite journal | vauthors = Berenbaum SA, Bryk KK, Nowak N, Quigley CA, Moffat S | title = Fingers as a marker of prenatal androgen exposure | journal = Endocrinology | volume = 150 | issue = 11 | pages = 5119–5124 | date = November 2009 | pmid = 19819951 | pmc = 2775980 | doi = 10.1210/en.2009-0774 }}</ref>