title: Digit ratio (2D:4D) and salivary testosterone, oestradiol and cortisol levels under challenge: Evidence for prenatal effects on adult endocrine responses.
abstract: BACKGROUND
  Digit ratio (2D:4D) is a marker for prenatal sex steroids and a correlate of sporting performance. This association may exist because low 2D:4D is linked to high prenatal levels of testosterone (T) and low oestrogens (E). It was recently suggested that low 2D:4D, and particularly low right-left 2D:4D (or Dr-l), is a marker for T changes in response to physical and aggressive challenges. If correct, this link may in part explain the association between 2D:4D and sports performance.
  
  
  OBJECTIVE
  We tested this hypothesis in adults.
  
  
  METHODS
  Three experimental treatments were completed using a randomised, cross-over design; (i) cycle sprints plus an aggressive video (S+V), (ii) aggressive video plus cycle sprints (V+S), and (iii) a control session.
  
  
  METHODS
  24 healthy adults (12 men and 12 women).
  
  
  METHODS
  Salivary T, oestradiol (E2) and cortisol (C) levels were measured on six occasions across each session and pooled for analysis.
  
  
  RESULTS
  The S+V treatment was associated with a rise in T and C levels, and Dr-l was significantly and negatively correlated with T and E2 with these effects confined to men. The right 2D:4D and Dr-l were also negatively correlated with the T/C ratio and Dr-l negatively related to the E2/C ratio in men during the S+V treatment.
  
  
  CONCLUSIONS
  We suggest that the hormonal responses to a challenge are programmed by prenatal levels of T and E with possible links to sporting performance in adulthood.
authors.affiliation: The Hamlyn Centre, Imperial College, London, UK. Electronic address: bcrewthe@imperial.ac.uk.
authors.forename: Blair
authors.initials: B
authors.lastname: Crewther
authors.affiliation: The Hamlyn Centre, Imperial College, London, UK; School of Sport, Health and Exercise Science, Bangor University, Gwynedd, UK.
authors.forename: Christian
authors.initials: C
authors.lastname: Cook
authors.affiliation: Applied Sports Technology, Exercise and Medicine Research Centre, Swansea University, Swansea, UK.
authors.forename: Liam
authors.initials: L
authors.lastname: Kilduff
authors.affiliation: Department of Psychology, Northumbria University, Newcastle-upon-Tyne, UK.
authors.forename: John
authors.initials: J
authors.lastname: Manning
mesh_terms: D000328:Adult; D054874:Athletic Performance; D004958:Estradiol / Q000378:metabolism*; D005260:Female; D005385:Fingers / Q000033:anatomy & histology*; D006801:Humans; D006854:Hydrocortisone / Q000378:metabolism*; D008297:Male; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects; D012463:Saliva / Q000378:metabolism*; D013739:Testosterone / Q000378:metabolism*
chemical_list: D013739:Testosterone; D004958:Estradiol; D006854:Hydrocortisone
keywords: Development; Exercise; Oestrogens; Stress; Testosterone