title: Adult digit ratio (2D:4D) is not related to umbilical cord androgen or estrogen concentrations, their ratios or net bioactivity.
abstract: BACKGROUND
  Ratio of second digit length to fourth digit length (2D:4D) has been extensively used in human and experimental research as a marker of fetal sex steroid exposure. However, very few human studies have measured the direct relationship between fetal androgen or estrogen concentrations and digit ratio.
  
  
  OBJECTIVE
  We investigated the relationships between both androgen and estrogen concentrations in umbilical cord blood and digit ratio in young adulthood. In addition we calculated measures of total serum androgen and total estrogen bioactivity and investigated their relationship to digit ratio.
  
  
  METHODS
  Prospective cohort study.
  
  
  METHODS
  An unselected subset of the Western Australian Pregnancy Cohort (Raine) Study (159 female; 182 male).
  
  
  METHODS
  Cord serum samples were collected immediately after delivery. Samples were assayed for androgen (testosterone, Δ4-androstenedione, dehydroepiandrosterone) and estrogen (estrone, estradiol, estriol, estetrol) concentrations using liquid-chromatography mass-spectrometry. Digit ratio measurements were taken from hand photocopies at age 19-22years.
  
  
  RESULTS
  For both males and females, there were no significant correlations between digit ratio and any androgen or estrogen concentrations considered individually, the testosterone to estradiol ratio, total androgen bioactivity measure or ratio of androgen to estrogen bioactivity (all p>.05). In males, but not females, total estrogen bioactivity was negatively correlated with left hand digit ratio (r=-.172, p=.02), but this relationship was no longer significant when adjusted for variables known to affect sex steroid concentrations in cord blood.
  
  
  CONCLUSIONS
  Our findings indicate that digit ratio is not related to fetal androgens or estrogens at late gestation.
authors.affiliation: Telethon Kids Institute, University of Western Australia, Australia; Neurocognitive Development Unit, School of Psychology, University of Western Australia, Australia. Electronic address: lauren.hollier@graduate.uwa.edu.au.
authors.forename: Lauren P
authors.initials: LP
authors.lastname: Hollier
authors.affiliation: School of Women's and Infant's Health, University of Western Australia, Australia.
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Keelan
authors.affiliation: Telethon Kids Institute, University of Western Australia, Australia; Neurocognitive Development Unit, School of Psychology, University of Western Australia, Australia.
authors.forename: Esha S L
authors.initials: ES
authors.lastname: Jamnadass
authors.affiliation: Neurocognitive Development Unit, School of Psychology, University of Western Australia, Australia.
authors.forename: Murray T
authors.initials: MT
authors.lastname: Maybery
authors.affiliation: Department of Obstetrics and Gynaecology, University of Melbourne and the Royal Women's Hospital, Victoria, Australia.
authors.forename: Martha
authors.initials: M
authors.lastname: Hickey
authors.affiliation: Telethon Kids Institute, University of Western Australia, Australia.
authors.forename: Andrew J O
authors.initials: AJ
authors.lastname: Whitehouse
mesh_terms: D000328:Adult; D000728:Androgens / Q000097:blood*; D004967:Estrogens / Q000097:blood*; D005260:Female; D005312:Fetal Blood / Q000378:metabolism*; D005385:Fingers / Q000033:anatomy & histology* / Q000254:growth & development; D006801:Humans; D008297:Male; D011247:Pregnancy
chemical_list: D000728:Androgens; D004967:Estrogens
keywords: 2D:4D; Androgens; Cord blood; Digit ratio; Estrogens; Raine study