title: Finger bone immaturity and 2D:4D ratio measurement error in the assessment of the hyperandrogenic hypothesis for the etiology of autism spectrum disorders.
abstract: Emerging hypotheses suggest a causal role for prenatal androgen exposure in some cases of autism spectrum disorders (ASD). The ratios of the lengths of the bones of the 2nd to the 4th digit (2D:4D) are purported to be markers for prenatal androgen exposure and to be established early in gestation. Elongation of the 4th digit in response to testosterone is said to reduce 2D:4D in males versus females. We examined the ratios of bones from the left hand radiographs of 75 boys and 6 girls 4-8 years of age, diagnosed with ASD, to evaluate digit ratio as a marker for gestational androgen exposure. Contrary to our expectations, girls had reduced 2D:4D compared to boys but the difference was not significant (Cohen's D 0.51-0.66, P>0.05). The limited sample size for this study and the absence of a referent group precluded providing robust estimates for girls and identifying possible statistical differences between the sexes. Tanner-Whitehouse 3 (TW3) rating of finger bone growth suggested relative immaturity of the 4th relative to the 2nd digits. Positive correlations were detected for 2D:4D ratios, body mass index (r=0.23, P=0.039), chronologic age (r=0.35, P=0.001), and skeletal age (r=0.42, P<0.0001). The TW3 ratings and associations between 2D:4D ratios and indicators of growth suggest that digits develop at different rates. This asynchronous development may produce differences in 2D:4D over time which could lead to erroneous interpretation of androgen exposure in utero among young ASD children.
authors.affiliation: Department of Environmental Health Sciences, University at Albany, State University of New York, Rensselaer, NY 12214, USA. mbloom@albany.edu
authors.forename: Michael S
authors.initials: MS
authors.lastname: Bloom
authors.forename: Allison S
authors.initials: AS
authors.lastname: Houston
authors.forename: James L
authors.initials: JL
authors.lastname: Mills
authors.forename: Cynthia A
authors.initials: CA
authors.lastname: Molloy
authors.forename: Mary L
authors.initials: ML
authors.lastname: Hediger
mesh_terms: D000328:Adult; D000728:Androgens / Q000009:adverse effects*; D000886:Anthropometry / Q000379:methods; D001321:Autistic Disorder / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000209:etiology*; D015415:Biomarkers; D002648:Child; D002675:Child, Preschool; D005260:Female; D050278:Finger Phalanges / Q000000981:diagnostic imaging* / Q000187:drug effects / Q000254:growth & development; D006801:Humans; D008297:Male; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects / Q000139:chemically induced / Q000000981:diagnostic imaging*; D011859:Radiography; D012307:Risk Factors; D012737:Sex Factors; D013739:Testosterone / Q000009:adverse effects*
chemical_list: D000728:Androgens; D015415:Biomarkers; D013739:Testosterone