The Second to Fourth FINGER Length Ratio(2D:4D) and Its Relationship with Body Composition Parameters in Korean Young Adults

Abstract

Purpose: Body composition status is influenced by changes in sex hormones, and this status is also closely related to normal daily life and the risk of various chronic diseases. On the other hand, the relative length of the second and fourth fingers(2D:4D ratio) has been proposed as a marker of prenatal androgen action of sensitivi-ty to testosterone, with a lower 2D:4D being associated with high androgen exposure.In this study, it was ex-amined the relationship between the 2D:4D ratio and various body composition parameters measured by bioe-lectric impedance analysis(BIA) in young adults to determine the usability of the 2D:4D ratio as a predictor of finger length- related diseases. Method: Ninety-three healthy individuals(60 men and 33 women, age 17-19 years) participated. Subjects’ body weight and height were measured, and body mass index(BMI) was calculated. Body fat mass, % body fat, % abdominal fat, skeletal mass, % muscle mass, and % bone mineral density was measured using BIA. SMI(skeletal muscle index) was calculated. The lengths of the second and fourth fingers of the right and left hands were measured using a electronic digital caliper, and the 2D:4D ratio and difference of the digit ratio between the right and left hands(Dr-l) were also calculated. The differences in anthropometric and body com-position variables between males and females was analyzed using independent t-test. Pearson’s correlation coefficient was used to determine the relationship between finger length measures(the 2D:4D ratio and Dr-l) and body composition parameters. The significance level was considered as p ≤ 0.05 at all stages. Results: In this study, significant sexually dimorphic differences were found in all results of the anthropomet-ric measures and body composition parameters, excluding Dr-l and % abdominal fat. The height and weight of men were significantly higher than that of women, and the variable related to fat-free mass of men among body composition was significantly higher than that of women. On the other hand, women were significantly higher than men in variables related to body fat mass. As the main findings about the correlation results be-tween the finger length measures and the body composition parameters, there was a significant difference in the 2D:4D ratio between males and females, but all variables except male muscle mass were not significantly correlated with finger length measures. Conclusion: Although the 2D:4D ratio has been proposed as a marker of prenatal androgen action and of sensitivity to testosterone, these results found in this study suggest that finger length measures may not be a preventive indicator for predicting body composition differences and diseases associated with sex hormones and finger length parameters.