Second to fourth digit ratio (2D:4D) and testosterone in men.
OBJECTIVE
To investigate the relationship between 2D:4D and testosterone in men attending an infertility clinic and men drawn from the general population.


METHODS
Data on 2D:4D and testosterone from two samples were collected: (1) 43 men attending an infertility clinic, and (2) 51 men drawn from the general population without regard to fertility.


RESULTS
In sample (1) there were negative associations between 2D:4D and testicular function, and men with lower 2D:4D in their right compared to left hand had higher testosterone levels than men with higher 2D:4D in their right compared to left hand. Sample (2) showed no significant associations between 2D:4D or side differences in 2D:4D and testosterone.


CONCLUSIONS
Adult levels of testosterone may be related to aspects of 2D:4D in samples which contain men with compromised testicular function, but not in men from normative samples. Associations between 2D:4D and fertility-associated traits probably arise from early organisational effects of testosterone rather than from activational effects of current testosterone.
Department of Psychology, University of Central Lancashire, Preston PR1 2HE, UK. jtmanning@uclan.ac.uk
J T
JT
Manning
S
S
Wood
E
E
Vang
J
J
Walton
P E
PE
Bundred
C
C
van Heyningen
D I
DI
Lewis-Jones
D000328:Adult; D005385:Fingers / Q000033:anatomy & histology*; D007839:Functional Laterality; D006801:Humans; D007248:Infertility, Male / Q000097:blood; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D012044:Regression Analysis; D013739:Testosterone / Q000097:blood*
D013739:Testosterone