Correlations between digit ratio and infertility in Chinese men.

Background: Digit ratio, especially second to fourth digit ratio (2D:4D) is lower in men than in women. The ratios of digit may be established in utero and is negatively correlated with sperm counts and testosterone in men and positively correlated with estrogen in men and women.

Aim: To study whether the digit ratio (especially 2D:4D) are associated with the a+b ratio of sperm number in Chinese populations.

Methods: Photocopies of the two hands of 268 men (controls: 72; patients: 196) and seminal parameters of masturbatory semen samples were collected.

Results: The mean values of digit ratio of the controls and the patients all presented a trend as 2D:3D<2D:4D<3D:4D<2D:5D<4D:5D<3D:5D; the patients have higher mean values than controls; significant variances of 2D:3D, 3D:4D (left: P<0.05; right: P ≤ 0.05) and 2D:4D (left: P<0.001; right: P<0.01) were found between two groups; there was a higher percentage of 2D>4D in the patients; the relationship between 2D:4D and a+b ratio of sperm number in the patients was significant (P<0.001).

Conclusion: Digit ratio, especially 2D:4D in the left hand maybe one of the important markers of infertility in men for early diagnosis.