Digit ratio (2D:4D) as an indicator of body size, testosterone concentration and number of children in human males (original) (raw)
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Human Biology Review, 2023
The second-to-fourth digit (2D:4D) ratio is a sexually dimorphic trait, with men having lower ratios than women, indicating relatively higher prenatal testosterone exposure compared to oestrogen. The 2D:4D ratio is fixed in intrauterine conditions that are affected by foetal sex steroids (testosterone and oestrogen) and an indirect method to determine intrauterine sex hormone levels that significantly correlate with somatic features, behavioural traits, fertility measures, reproductive characteristics, and predisposition to certain chronic diseases. Researchers discovered that a more masculine (low 2D<4D) digit ratio and a more feminine (high; 2D>4D) digit ratio are manifestations of increased prenatal testosterone and oestrogen exposure, respectively. Furthermore, digit ratio (2D:4D) values are widely used to predict reproductive capacity and success, fertility measures, natural menopause, and age at menarche, which varies between populations. The current review paper attempted to discuss sexual dimorphism in 2D:4D ratios, as well as its potential association and utility in evaluating certain reproductive characteristics and behavioural traits in populations. Methodological comparisons, benefits and drawbacks of determining the 2D:4D for studying the effect of prenatal sex steroids are also highlighted.
Journal of research in medical sciences : the official journal of Isfahan University of Medical Sciences, 2014
Ratio of second and fourth digit (2D:4D) is known to be germane in analyzing utero concentrations of testosterone and estrogen in human and other vertebrates. 2D:4D had been linked to several traits like athletes' abilities, reproductive success, risk of cancer and cardiovascular disease (CVD). Metabolic syndrome (MetS) is a clustering of several cardiovascular risk factors. Waist circumference (WC), neck circumference (NC), body mass index (BMI) and waist-to-height ratio (WHtR) are important in measuring MetS. This study investigated sexual dimorphism in 2D:4D and its relationship with MetS indices and CVD factors among adult residing in Ilorin, North central Nigeria. This is a cross-sectional, stratified multi-staged sampling study. Participants residing in different neighborhoods were visited at home where finger lengths and anthropometric traits were measured. Participants include 801 healthy adults aged 18-44 years (56% male) who had been living in the area for more than 3 ...
Digit ratio (2D:4D) in newborns: Influences of prenatal testosterone and maternal environment
Early Human Development, 2013
Introduction: The 2D:4D digit ratio is sexually-dimorphic, probably due to testosterone action through the perinatal period. We characterize the 2D:4D ratio in newborn (NB) infants, in between the pre-and postnatal surges of testosterone, and relate it to the mother's 2D:4D and to testosterone levels in the amniotic fluid (AF). Subjects and methods: Testosterone was assayed in samples of maternal plasma and AF collected at amniocentesis. Shortly after birth, 106 NBs and their mothers were measured for 2D:4D ratio. Results: NB males had lower mean 2D:4D ratios than females but this dimorphism was significant only for the left hand (males: 0.927; females: 0.950; p =0.004). Mothers who had sons had lower 2D:4D ratios than those who had daughters and the mother's 2D:4D were higher than those of NBs regardless of sex. Both hands of NB females were negatively correlated with AF testosterone and positively correlated with the mother's 2D:4D, but males showed no significant associations. Maternal plasma testosterone also showed a negative weak correlation with NB's digit ratio in both sexes. Conclusions: Sexual dimorphism at birth was only significant for the left hand, in contrast with reports of greater right hand dimorphism, suggesting that postnatal testosterone is determinant for 2D:4D stabilization. The lower 2D:4D ratios in mothers who had sons support claims that hormone levels in parents are influential for determining their children's sex. NB female's digit ratio, but not males', was associated to the level of AF testosterone. The mother's 2D:4D ratios were positively correlated with their daughters' 2D:4D, but the same was not observed for male NBs, suggesting that prenatal testosterone levels in male fetus lead their 2D:4D ratios to stray from their mothers' with high individual variability.
Digit ratio (2D:4D) and testosterone supplementation
Early Human Development, 2019
Background: Testosterone (T) is taken or prescribed to enhance appearance, increase athletic performance and libido and to treat hypogonadism. Digit ratio (2D:4D) is thought to be a negative correlate of prenatal T. Here we consider the relationship between 2D:4D and T supplementation. Aims: Our sample was taken from the BBC internet study. Respondents were asked (y/n) if they were taking; (i) T, (ii) hormone replacement therapy with T (HRTwT). We removed extreme 2D:4D values and age and considered the most numerous ethnic group (i.e. "Whites"). Analyses were performed with a two-factor (sex*T) analysis of variance with covariate age and dependent variables 2D:4D or right-left 2D:4D (Dr-l). Results: Out of 197,589 respondents, 793 (598 males) reported taking T. There was a significant main effect for right 2D:4D such that T supplementing males had higher 2D:4D than those who did not. The sex*T interaction was significant, but the effect reversed in females. There were 22,576 (661 males) participants who reported taking HRTwT. We found a significant main effect for right 2D:4D, males taking HRTwT had higher 2D:4D than those who did not. This was reversed in females. The sex*HRTwT interaction was significant, a high Dr-l was also found in males reporting HRTwT. Conclusion: Males who reported taking T or HRTwT had high right 2D:4D and/or Dr-l. The situation with females may be the reverse of that found in males but effect sizes are less. The health implications of an association between high (feminized) 2D:4D and T supplementation in males are discussed. 1.1. Testosterone supplementation The use of T and its synthetic analogs are sex and age dependent. In general, it is males and the young rather than females and the old who take T [16]. Their use without medical prescription is illegal in the US and Canada and, in the UK, it is illegal to supply T. Nevertheless, such
2nd to 4th digit ratios, foetal testosterone and estradiol
Background: The ratio of 2nd to 4th digit length (2D:4D) is sexually dimorphic (mean 2D:4D is lower in males than females) and is thought to be fixed early in development. 2D:4D has been reported to be related to fetal growth, hand preference, autism, Asperger's syndrome, sperm counts, family size, age at myocardial infarction in men and breast cancer in women. There is indirect evidence that 2D:4D is established in utero and is negatively related to prenatal testosterone and positively with prenatal estradiol. However, there are no studies which show direct relationships between fetal testosterone (FT), fetal estradiol (FE) and 2D:4D. Aims: To investigate the relationships between 2D:4D ratios and FT and FE from amniotic fluid. Study design: Cohort study. Subjects: 33 children. Outcome measures: Radioimmunoassays of FT and FE obtained from routine amniocentesis; 2D:4D ratios calculated from 2nd and 4th digit length of the right and left hands at age 2 years. Results: A significant negative association between right 2D:4D ratio and FT/FE ratio, which was independent of sex. Conclusions: These preliminary findings lend support to an association between low 2D:4D and high levels of FT relative to FE, and high 2D:4D with low FT relative to FE.
Second to fourth digit ratio, adult testosterone level and testosterone deficiency
BJU International, 2012
The ratio of the second and fourth finger lengths (2D/4D) is related to intrauterine exposure to testosterone. The relationship between 2D/4D and adult hormonal pattern is controversial. The aim of our study was to determine if there was a relationship between adult serum testosterone levels and the 2D/4D ratio. We prospectively recruited 204 consecutive patients referred for transrectal prostate biopsy between January 2008 and June 2009. The same physician performed clinical examinations, 2D/4D measurements and the transrectal biopsy in all cases. Cut-off points of 231 and 346 ng/dL testosterone (8 and 12 nmol/L) were used. 2D/4D determination was done with a vernier calliper on the left hand. The hormonal profile (testosterone and sexual hormone binding globulin) of the patients was determined between 7.00 am and 11.00 am. Age, weight, height, body mass index, toxic habits, digital rectal examination, prostate-specific antigen and 2D and 4D measurements were recorded prospectively. The mean age was 67 ± 7 years and the mean testosterone level was 413 ± 18 ng/dL (14.33 ± 0.62 nmol/L). The percentages of patients with testosterone &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;231 ng/dL (8 nmol/L) and testosterone &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;346 ng/dL (12 nmol/L) were 6.1 and 30.6 respectively. Univariate analysis showed that low 2D/4D ratios were related to higher levels of testosterone (B=-741.98; β=-0.165, P= 0.045) and also with low prevalence of biochemical hypogonadism (testosterone &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;346 ng/dL). Mean 2D/4D ratio in patients with testosterone &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;346 ng/dL was lower than in patients with testosterone &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;346 ng/dL (2D/4D 0.97 ± 0.037 vs 0.99 ± 0.043 depending on their hormonal status, P= 0.05). High 2D/4D ratio was associated with low testosterone serum levels (P= 0.046). The 2D/4D ratio is related to adult testosterone levels and the presence of testosterone deficiency syndrome. Patients with high 2D/4D ratios have lower testosterone levels and higher risk of testosterone deficiency syndrome.
The 2nd:4th digit ratio, sexual dimorphism, population differences, and reproductive success
Evolution and Human Behavior, 2000
The ratio between the length of the 2nd and 4th digit (2D:4D) is sexually dimorphic, with mean male 2D:4D lower than mean female 2D:4D. It recently was suggested that 2D:4D is negatively correlated with prenatal testosterone and positively correlated with prenatal estrogen. It is argued that high prenatal testosterone and low estrogen (indicated by low 2D:4D) favors the male fetus and low prenatal testosterone and high estrogen (indicated by high 2D:4D) favors the female fetus. The patterns of expression of 2D:4D are interpreted in terms of sexually antagonistic genes.
Physical Fitness And Digit Ratio (2D:4D) In Male Students From Wrocław, Poland
There is sex-difference in humans as regards aerobic efficiency, physical strength and endurance and the sex difference is greatly dependent upon differential concentration of testosterone during different phases of growth and development including the intrauterine phase or prenatal growth. Second-to-fourth digit lengths ratio (2D:4D) is an putative indicator of prenatal testosterone exposure. Lower 2D:4D indicates higher prenatal testosterone exposure and vice versa. Males generally have lower 2D:4D than females. This cross-sectional study investigated the relationship between the fitness measures and 2D:4D in young adult Polish males. The study included 118 Polish male students first course in General Kościuszko Military Academy of Land Forces in Wroclaw. Their mean (+SD) age was 20.4 (+1.60) years. Eurofit test set was employed to assess physical fitness. Apart from height, weight, second and fourth digit lengths, hand grip strength was also measured by a standard isometric dynamometer. The study showed a weak relationship between 2D:4D of right hand and results of physical fitness tests. The smaller was the 2D:4D, the better was the result of endurance and strength tests. This finding was in accord with reports by other studies, indicating that individuals with smaller 2D:4D tend to perform better in these aspects of physical ability. However, we also found an opposite relationship with the results to agility tests. Male students with higher 2D:4D scored better in 5x10 meters shuttle run. This finding did not match with results reported by other studies. This study indicated towards possibility that an association between low 2D:4D and sport and athletic achievement and also physical performances were due to, at least in part, the action of prenatal testosterone. Further studies are required to investigate the relationship of fitness parameters with digit ratio and ultimately with prenatal testosterone exposure. Key words: Eurofit test, 2D:4D, digit ratio, testosterone, male, Poland