title: Second to fourth digit ratio, handedness and testicular germ cell tumors.
abstract: BACKGROUND
  Research on early life exposures and testicular germ cell tumors (TGCT) risk has focused on a possible perinatal etiology with a well-known hypothesis suggesting that hormonal involvement during fetal life is associated with risk. Second-to-fourth digit ratio (2D:4D) and left-hand dominance have been proposed as markers of prenatal hormone exposure.
  
  
  OBJECTIVE
  To evaluate associations between 2D:4D digit ratio, right minus left 2D:4D (ΔR-L), and left-hand dominance and TGCT in the U.S. Servicemen's Testicular Tumor Environmental and Endocrine Determinants Study.
  
  
  METHODS
  A total of 246 TGCT cases and 236 non-testicular cancer controls participated in the current study, and completed a self-administered questionnaire. Associations between digit ratio, hand dominance and TGCT were estimated using unconditional logistic regression adjusting for identified covariates.
  
  
  RESULTS
  Right 2D:4D was not associated with TGCT [odds ratio (OR) for a one-standard deviation (SD) increase in right-hand 2D:4D: 1.12, 95% confidence interval (CI): 0.93-1.34]. The results were consistent when evaluating the association based on the left hand. The difference between right and left-hand 2D:4D was also not associated with TGCT risk [OR for a one-SD increase in ΔR-L: 1.03, 95% CI: 0.87-1.23]. Compared to men who reported right-hand dominance, ambidexterity [OR (95% CI)=0.65 (0.30-1.41)] and left-hand dominance [OR (95% CI)=0.79 (0.44-1.44)] were not associated with risk.
  
  
  CONCLUSIONS
  These results do not support the hypothesis that prenatal hormonal imbalance is associated with TGCT risk. Given the limited sample size, further evaluation of the relationship between TGCT and prenatal hormonal factors using digit ratio, ΔR-L, or left-hand dominance and larger sample size are warranted.
authors.affiliation: Hormonal and Reproductive Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Rockville, MD 20852-7234, USA. trabertbl@mail.nih.gov
authors.forename: Britton
authors.initials: B
authors.lastname: Trabert
authors.forename: Barry I
authors.initials: BI
authors.lastname: Graubard
authors.forename: Ralph L
authors.initials: RL
authors.lastname: Erickson
authors.forename: Yawei
authors.initials: Y
authors.lastname: Zhang
authors.forename: Katherine A
authors.initials: KA
authors.lastname: McGlynn
mesh_terms: D000293:Adolescent; D000328:Adult; D016022:Case-Control Studies; D005385:Fingers / Q000033:anatomy & histology*; D007839:Functional Laterality; D006801:Humans; D008297:Male; D018239:Seminoma / Q000175:diagnosis*; D013736:Testicular Neoplasms / Q000175:diagnosis*