Digit ratio (2D:4D) as an indicator of body size, testosterone concentration and number of children in human males

@article{Klimek2014DigitR,
  title={Digit ratio (2D:4D) as an indicator of body size, testosterone concentration and number of children in human males},
  author={Magdalena Klimek and Andrzej Galbarczyk and Ilona Nenko and Louis Calistro Alvarado and Grazyna Jasienska},
  journal={Annals of Human Biology},
  year={2014},
  volume={41},
  pages={518 - 523}
}
OBJECTIVES The 2nd to 4th digit ratio (2D:4D) is thought to reflect exposure to androgens during foetal development. [] Key Method Life history data and anthropometric measurements were collected. Salivary morning and evening testosterone levels among 110 men from the same population were measured.
Association between the digit ratio (2D:4D) and body fat distribution in Mordovian students
TLDR
The association between the 2D:4D ratio and skinfold thickness is indicative of the role of prenatal sex hormones in shaping the body fat distribution in females, along with the significant impact of sex hormones at puberty.
Women with more feminine digit ratio (2D:4D) have higher reproductive success.
TLDR
It is indicated that women with more feminine 2D:4D had higher reproductive success and there might be other biological pathways explaining the observed results, that is, via behaviors that were indirectly related to fertility.
Second-to-fourth digit ratio (2D:4D) is unrelated to measures of somatic reproductive effort among young men from Cebu, the Philippines.
TLDR
Test the hypothesis that the association of low 2D:4D ratios with increased muscularity and decreased adiposity depends on current testosterone (T) levels, such that digit ratio will be a particularly strong predictor of outcomes among men exhibiting a mating-effort-oriented endocrine profile (high T).
Association of the digit ratio (2D:4D) with sexually dimorphic morphological traits
TLDR
The association of 2D:4D ratio with morphological signs of masculinity/femininity within male and female samples were revealed only as a trend, which was more distinct for the functional indicators (handgrip strength).
Association patterns between 2D:4D ratio and age at menarche: the impact of methodology
Abstract The ratio of index finger to ring finger length (2D:4D) is a sexually dimorphic feature and widely used as an indicator of prenatal androgen-estrogen exposure. Several studies have
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
TLDR
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.
Female digit length ratio (2D:4D) and time-to-pregnancy.
TLDR
The data do not provide evidence for an association between female 2th- to 4th-finger ratio and fecundity as measured by time-to-pregnancy (TTP), and there was no evidence of diminished/increased fecundability according to the 2D:4D, neither on the right nor on the left hand.
Relationship between second to fourth digit ratio (2D:4D) and academic performance among students in Nigeria.
The second to fourth digit ratio (2D:4D), is a sexually dimorphic trait, with males on the average having lower ratios than females 2D:4D. It had been correlated with several psychosocial features.
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
TLDR
The development of excessive body weight in men and women, and fat accumulation in the upper arms, thighs and lower legs in women with obesity (but not men) are associated with increased prenatal estrogen exposure, which indicates a new area of activity in the field of obesity prevention.
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References

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Sexual Dimorphism and Relationship between Chest, Hip and Waist Circumference with 2D, 4D and 2D:4D in Nigerians
TLDR
This study strongly confirms the sexually dimorphic nature of 2D:4D, even though it fails to show relationship between 2D-4D and BMI, chest, waist and hip circumferences as reported in other studies.
Relationship between Digit Ratio (2D:4D) and Birth Weight in Nigerians
TLDR
This study has demonstrated the association between 2D:4D and birth weight andBirth weight could be predicted most especially form the left hands, but the predictive ability lies more in theleft hands in both males and females.
Digit ratio (2D:4D) and handgrip strength in subjects of Han ethnicity: impact of sex and age.
TLDR
There was a sex-specific correlation between 2D:4D and handgrip strength, and this relationship may be driven by sexual selection operating on fetal programming.
Second to fourth digit ratio (2D:4D) and testosterone in men.
TLDR
Adult levels of testosterone may be related to aspects of 2D:4D in samples which contain men with compromised testicular function, but not in men from normative samples.
Digit ratio (2D:4D), dominance, reproductive success, asymmetry, and sociosexuality in the BBC Internet Study
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    American journal of human biology : the official journal of the Human Biology Council
  • 2008
TLDR
The BBC Internet Study of sex differences in which finger lengths were self‐measured shows sexual dimorphism, ethnic differences and higherDimorphism of right 2D:4D than left, thereby indicating that 2D-4D does measure real between‐participant variation.
Association of Height and Weight with Second to Fourth Digit Ratio (2D:4D) and Sex Differences
TLDR
The results suggest that height of adults reflecting prenatal hormone status may play a role in differences between men and women in 2D:4D digit ratio for right-handers.
A study of finger lengths, semen quality and sex hormones in 360 young men from the general Danish population.
TLDR
This relatively large study of young, normal Danish men shows no reliable association between 2D:4D finger ratio and testicular function and statistically significant results may be 'false positives' rather than representing true associations.
Second to fourth digit ratio (2D:4D) and concentrations of circulating sex hormones in adulthood
TLDR
There were no strong associations between any adult circulating concentration of sex hormone or SHGB measured in adulthood and 2D:4D, and these results contribute to the growing body of evidence indicating that 2D:[4D]4D is unrelated to adult sex hormone concentrations.
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