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.
AIM: 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.