Correlations between digit ratio and infertility in Chinese men

Area of Science:

• Endocrinology and Reproductive Biology
• Anthropometry and Human Variation

Background:

• Digit ratio, particularly the second to fourth digit ratio (2D:4D), exhibits sexual dimorphism, being lower in males than females.
• Prenatal hormone exposure influences digit ratio, correlating with reproductive hormone levels like testosterone and estrogen.
• Digit ratio may serve as a biomarker for prenatal androgen exposure and subsequent reproductive health.

Purpose of the Study:

• To investigate the association between digit ratios (especially 2D:4D) and sperm number (a+b ratio) in a Chinese male population.
• To determine if digit ratio can serve as a predictive marker for male infertility.

Main Methods:

• Collection of hand digit ratio photocopies from 268 Chinese men (72 controls, 196 patients).
• Analysis of seminal parameters, including sperm count (a+b ratio), from masturbatory semen samples.
• Statistical comparison of digit ratios and seminal parameters between control and patient groups.

Main Results:

• Significant differences in mean digit ratios (2D:3D, 3D:4D, and 2D:4D) were observed between control and patient groups, particularly in the left hand.
• A higher prevalence of 2D>4D was noted in patients with infertility.
• A strong significant correlation (P<0.001) was found between the left-hand 2D:4D ratio and the a+b ratio of sperm number in infertile men.

Conclusions:

• The second to fourth digit ratio (2D:4D), especially in the left hand, is a significant indicator associated with sperm number.
• Left-hand 2D:4D ratio may serve as a valuable, non-invasive marker for the early diagnosis of male infertility in Chinese populations.