Association of prenatal sex steroid exposure estimated by the digit ratio (2D:4D) with birth weight, BMI and muscle strength in 6- to 13-year-old Polish children

Abstract

Objectives The aim of this paper was to provide evidence for the impact of prenatal sex steroid exposure on prenatal and postnatal body size parameters, and muscle strength in children. Methods The following anthropometric data were studied in a group of 1148 children (536 boys and 612 girls) aged 6–13 years: the 2D:4D digit ratio, birth weight and length, and birth head and chest circumference. Postnatal parameters (6–13 years) included body weight and height, BMI, waist and hip circumference, WHR, as well as grip strength in both hands. All parameters that required it were adjusted for sex and gestational or chronological age. A general linear model, Pearson’s correlation, t-statistics and Cohen’s Δ were used in statistical analysis. Results Among birth size parameters, only birth weight was significantly negatively correlated with the 2D:4D digit ratio in children. Higher (feminized) digit ratios were significantly correlated with postnatal parameters such as body weight, BMI, and waist and hip circumference (positively), as well as hand grip strength–a proxy for muscular strength (negatively). Conclusion Problems with maintaining adequate body size parameters and muscle strength may be programmed in fetal life and predicted on the basis of the 2D:4D digit ratio. Body weight at birth and in early ontogenesis are additive correlates of the 2D:4D ratio. The present findings suggest that the 2D:4D digit ratio is related to postnatal phenotypes such as birth weight, overweight, and obesity as well as muscle strength in 6–13-year-old children of both sexes.

The 2D:4D index is associated with the development of excess body weight in adults, but not with the rate of weight loss following bariatric surgery

“…Many other authors have also demonstrated that 2D:4D not only of the right hand, but also of the left hand, positively correlates with body mass index (BMI) in adults of both sexes 32 , 33 . Other research revealed a positive relationship between BMI and 2D:4D, but only for the right hand 34 , 35 . On the other hand, Fink et al found that BMI in men (but not in women) is positively related to the digit ratio, but it remains significant only for the left hand 36 .…”

No evidence for a causal contribution of bioavailable testosterone to ADHD in sex-combined and sex-specific two-sample Mendelian randomization studies

“…However, while the 2D:4D ratio is often seen as a surrogate marker for intrauterine testosterone exposure, the observation of a missing association of testosterone levels in amniotic fluid with the 2D:4D ratio only recently failed to confirm this idea [27], a finding questioning the validity of this measure. In addition, it has been shown that the 2D:4D length ratio varies, e.g., with maternal smoking [31] or birth weight [17], which are both not per se associated with intrauterine testosterone exposure.…”

Evaluation of digit ratio (2D:4D) in breast cancer patients

“…In other studies on children, the relationship between 2D:4D ratio and cortisol, vitamin D level and body composition, and the relationship between 2D:4D ratio and fitness level were evaluated 23 , 24 . There are studies suggesting that prenatal sex steroid exposure may be a risk factor for migraine in adults and may be associated with birth weight, BMI and muscle strength in children 25 , 26 .…”