Purpose: To investigate the relationship between the ratio of index to ring finger lengths (2D:4D ratio), reflecting androgen exposure in utero, and reproductive function among men.
Methods: Male patients (N = 180) who consulted for fertility issues participated in the study. The palms of both hands were scanned, and the 2D:4D ratio was calculated. Data on semen volume, sperm concentration and total motility, total and motile sperm counts, and serum hormone concentrations were obtained. Spearman correlation coefficients between the 2D:4D ratio and hormone and semen quality parameters were calculated.
Results: The total sperm count was significantly negatively correlated with the 2D:4D ratio of the left hand (r = -0.154, p = 0.039) but not with that of the right hand (r = -0.045, p = 0.548). Testosterone showed weak negative correlations with the 2D:4D ratio in the left (r = -0.142, p = 0.058) and right (r = - 0.149, p = 0.046) hands. Follicle-stimulating hormone levels were negatively correlated with the 2D:4D ratios of the left (r = -0.173, p = 0.020) and right (r = -0.164, p = 0.027) hands. Other semen quality parameters or luteinizing hormone levels showed no significant correlation with the 2D:4D ratios.
Conclusions: No clear associations were observed between the 2D:4D ratios and reproductive function.
Keywords: androgens; digit ratio; hormone; male infertility; semen quality.
© 2023 The Authors. Reproductive Medicine and Biology published by John Wiley & Sons Australia, Ltd on behalf of Japan Society for Reproductive Medicine.