Finger Length Ratio Research Articles

Genetic Variations in the Androgen Receptor Are Associated with Steroid Concentrations and Anthropometrics but Not with Muscle Mass in Healthy Young Men

ObjectiveThe relationship between serum testosterone (T) levels, muscle mass and muscle force in eugonadal men is incompletely understood. As polymorphisms in the androgen receptor (AR) gene cause differences in androgen sensitivity, no straightforward correlation can be observed between the interindividual variation in T levels and different phenotypes. Therefore, we aim to investigate the relationship between genetic variations in the AR, circulating androgens and muscle mass and function in young healthy male siblings.Design677 men (25–45 years) were recruited in a cross-sectional, population-based sibling pair study.MethodsRelations between genetic variation in the AR gene (CAGn, GGNn, SNPs), sex steroid levels (by LC-MS/MS), body composition (by DXA), muscle cross-sectional area (CSA) (by pQCT), muscle force (isokinetic peak torque, grip strength) and anthropometrics were studied using linear mixed-effect modelling.ResultsMuscle mass and force were highly heritable and related to age, physical activity, body composition and anthropometrics. Total T (TT) and free T (FT) levels were positively related to muscle CSA, whereas estradiol (E2) and free E2 (FE2) concentrations were negatively associated with muscle force. Subjects with longer CAG repeat length had higher circulating TT, FT, and higher E2 and FE2 concentrations. Weak associations with TT and FT were found for the rs5965433 and rs5919392 SNP in the AR, whereas no association between GGN repeat polymorphism and T concentrations were found. Arm span and 2D:4D finger length ratio were inversely associated, whereas muscle mass and force were not associated with the number of CAG repeats.ConclusionsAge, physical activity, body composition, sex steroid levels and anthropometrics are determinants of muscle mass and function in young men. Although the number of CAG repeats of the AR are related to sex steroid levels and anthropometrics, we have no evidence that these variations in the AR gene also affect muscle mass or function.

Finger length ratios in Serbian transsexuals.

Atypical prenatal hormone exposure could be a factor in the development of transsexualism. There is evidence that the 2nd and 4th digit ratio (2D : 4D) associates negatively with prenatal testosterone and positively with estrogens. The aim was to assess the difference in 2D : 4D between female to male transsexuals (FMT) and male to female transsexuals (MFT) and controls. We examined 42 MFT, 38 FMT, and 45 control males and 48 control females. Precise measurements were made by X-rays at the ventral surface of both hands from the basal crease of the digit to the tip using vernier calliper. Control male and female patients had larger 2D : 4D of the right hand when compared to the left hand. Control male's left hand ratio was lower than in control female's left hand. There was no difference in 2D : 4D between MFT and control males. MFT showed similar 2D : 4D of the right hand with control women indicating possible influencing factor in embryogenesis and consequently finger length changes. FMT showed the lowest 2D : 4D of the left hand when compared to the control males and females. Results of our study go in favour of the biological aetiology of transsexualism.

Spatial abilities are not related to testosterone levels and variation in the androgen receptor in healthy young men

Androgens modulate brain functions such as cognition, emotions and ability. Several studies have shown a correlation between testosterone levels and mental rotation. The aim of the present study was to confirm the influence of salivary testosterone levels, 2D/4D ratio (such as a putative marker of prenatal testosterone), and sensitivity of androgen receptor on the mental rotation in healthy young men. Seventy-five healthy young men (age, 21.86 year) volunteered in this study. Mental rotation scores of our subjects were assessed using the Vandenberg and Kuse Mental Rotation Test. The 2D/4D finger length ratio as an indicator of prenatal testosterone was used as an average measurement of both hands. Correlation analysis revealed no correlation between salivary testosterone levels and mental rotation. However, we have observed a trend towards a negative correlation. There were no statistically significant results between 2D/4D ratio and mental rotation or between polymorphic three-nucleotide (CAG) repeats and mental rotation tests. Future studies should focus on other genetic determinants of spatial abilities, potentially genes involved in testosterone metabolism.

Gender identity disorder and schizophrenia: neurodevelopmental disorders with common causal mechanisms?

Gender identity disorder (GID), recently renamed gender dysphoria (GD), is a rare condition characterized by an incongruity between gender identity and biological sex. Clinical evidence suggests that schizophrenia occurs in patients with GID at rates higher than in the general population and that patients with GID may have schizophrenia-like personality traits. Conversely, patients with schizophrenia may experience alterations in gender identity and gender role perception. Neurobiological research, including brain imaging and studies of finger length ratio and handedness, suggests that both these disorders are associated with altered cerebral sexual dimorphism and changes in cerebral lateralization. Various mechanisms, such as Toxoplasma infection, reduced levels of brain-derived neurotrophic factor (BDNF), early childhood adversity, and links with autism spectrum disorders, may account for some of this overlap. The implications of this association for further research are discussed.

Finger lengths and behavior: Is the 2D:4D index of interest in forensic medicine?

ABSTRACT The relationship between the second and the fourth digit in the human hand, the 2D:4D index, is considered a putative marker of exposure to prenatal testosterone. Much research has been done in the attempt to associate the 2D:4D index and physical characteristics as well as cognitive skills and behavioral patterns. It has been suggested that these characteristics and behavioral patterns may be linked to high levels of testosterone. The basis for considering the 2D:4D index a marker of prenatal exposure to testosterone, and the influence of prenatal and circulating testosterone on behavior are reviewed. Furthermore, it is discussed whether forensic medicine may benefit from identification of a marker of behavioral predispositions. It seems that it is not possible to derive any valid information on predispositions from finger length ratio, however the field of 2D:4D research might benefit from forensic studies.

Digit Ratio (2D:4D) and Body Composition in Athletes

In the course of previous studies it has been established that finger length ratio (2D:4D) can be used as a marker of prenatal androgens exposition. Its low level is connected with a high prenatal and postnatal testosterone level. 2D:4D ratio proves helpful during the evaluation of athletes' predisposition to practice certain disciplines. The study included a group of athletes - 72 men and 60 women - aged between 18 and 36. Physiotherapy and dietetics students (140) from the Torun University Collegium Medicum and tourism and recreation students (63) from the Bydgoszcz University were the control group. Body height and the length of 2 nd and 4 th finger of right hand were measured in each subject, as well as body composition with the method of segmental bioelectrical impedance analysis (SBIA). The study concerned the dependence between the digit ratio (2D:4D) and a series of selected features and body composition indicators in athletes of both sexes, as well as the comparison of 2D:4D ratio in athletes and less physically active subjects. In studied female athletes a significant correlation was found between finger length ratio 2D:4D and total and active body mass, and BMI. 2D:4D ratio was not significantly lower when compared to the women who were not athletes. Hormone dependent 2D:4D ratio was finitely predictive in male athletes.

The correlation of right 2D:4D finger length ratio to the low-grade inflammation marker IL-6 in children. The Healthy Growth Study

BackgroundSecond to fourth digit ratio (2D:4D) is associated with cardiometabolic risk in adults. AimTo examine the association of right 2D:4D with cardiovascular disease risk factors in children. Study designCross-sectional study. SubjectsA sample of 301 children (53.5% girls) aged 9–13 in Greece and their parents. Children who were sick during the previous week of examination (n=44) were excluded from the analyses. Outcome measuresSocio-demographic (gestational age, birth weight, age, gender, maternal education level), anthropometric (body weight and height, finger length), clinical (pubertal stage, sickness during the previous week of the examination), blood [serum high sensitivity C-reactive protein (CRP), serum high sensitivity interleukin-6 (IL-6), serum leptin], lifestyle (dietary intake, maternal smoking during pregnancy) and physical fitness (handgrip strength) data were collected. CRP, IL-6 and leptin were measured with ELISA, using standard equipment and procedures, in accordance with manufacturers' instructions. ResultsFull data were available for 257 children (52.1% girls). The rank values of right 2D:4D and IL-6 were included in the analyses. Right 2D:4D was correlated only with IL-6 at a bivariate level (r=0.216, p=0.012) in girls. At a linear multivariate level, this association remained significant, even after adjusting for several potential confounders such as age, Tanner stage, maternal education level, body mass index, maternal smoking during pregnancy, duration of pregnancy, protein-, carbohydrate-, fat-intake and physical fitness (β±SE=0.220±0.066, p=0.001). ConclusionsRight 2D:4D was found to be associated with IL-6 in girls. Right 2D:4D may be a valuable, simple screening tool of low-grade inflammation in children.

Biological Markers of Asexuality: Handedness, Birth Order, and Finger Length Ratios in Self-identified Asexual Men and Women

Human asexuality is defined as a lack of sexual attraction to anyone or anything and it has been suggested that it may be best conceptualized as a sexual orientation. Non-right-handedness, fraternal birth order, and finger length ratio (2D:4D) are early neurodevelopmental markers associated with sexual orientation. We conducted an Internet study investigating the relationship between self-identification as asexual, handedness, number of older siblings, and self-measured finger-lengths in comparison to individuals of other sexual orientation groups. A total of 325 asexuals (60 men and 265 women; M age, 24.8 years), 690 heterosexuals (190 men and 500 women; M age, 23.5 years), and 268 non-heterosexuals (homosexual and bisexual; 64 men and 204 women; M age, 29.0 years) completed online questionnaires. Asexual men and women were 2.4 and 2.5 times, respectively, more likely to be non-right-handed than their heterosexual counterparts and there were significant differences between sexual orientation groups in number of older brothers and older sisters, and this depended on handedness. Asexual and non-heterosexual men were more likely to be later-born than heterosexual men, and asexual women were more likely to be earlier-born than non-heterosexual women. We found no significant differences between sexual orientation groups on measurements of 2D:4D ratio. This is one of the first studies to test and provide preliminary empirical support for an underlying neurodevelopmental basis to account for the lack of sexual attraction characteristic of asexuality.

Prenatal testosterone and preschool Disruptive Behavior Disorders

Disruptive Behavior Disorders (DBD), including Oppositional-Defiant Disorder (ODD) and Attention-Deficit/Hyperactivity Disorder (ADHD), are fairly common and highly impairing childhood behavior disorders that can be diagnosed as early as preschool. Prenatal exposure to testosterone may be particularly relevant to these early-emerging DBDs that exhibit a sex-biased prevalence rate favoring males. The current study examined associations between preschool DBD symptom domains and prenatal exposure to testosterone measured indirectly via right 2D:4D finger-length ratios. The study sample consisted of 109 preschool-age children between ages 3 and 6 (64% males; 72% with DBD) and their primary caregivers. Primary caregivers completed a semi-structured interview (i.e., Kiddie Disruptive Behavior Disorder Schedule), as well as symptom questionnaires (i.e., Disruptive Behavior Rating Scale, Peer Conflict Scale); teachers and/or daycare providers completed symptom questionnaires and children provided measures of prenatal testosterone exposure, measured indirectly via finger-length ratios (i.e., right 2D:4D). Study results indicated a significant association of high prenatal testosterone (i.e., smaller right 2D:4D) with high hyperactive–impulsive ADHD symptoms in girls but not boys, suggesting that the effect may be driven by, or might only exist in, girls. The present study suggests that prenatal exposure to testosterone may increase risk for early ADHD, particularly hyperactivity–impulsivity, in preschool girls.

Second to fourth digit ratio confirms aggressive tendencies in patients with boxers fractures

BackgroundUpper limb second to fourth digit ratio (2D:4D) has been shown to be dependent on prenatal androgen exposure. A longer relative fourth digit to second digit is indicative of increased intrauterine testosterone exposure prenatally and the converse is also true for oestrogen exposure. The 2D:4D ratio has implications in the sporting, academic, financial and sexual arenas. The purpose of this study was to examine the association between smaller finger length ratios (2D:4D) and boxers fractures, in both men and women, by comparing the 2D:4D ratios in 150 boxers fractures and comparing them to matched controls. Boxers fractures are an injury classically incurred during acts of aggression and we postulated that this cohort of patients would have a smaller 2D:4D ratio in comparison to the normal population mean ratio. MethodsOne hundred and fifty radiographs from patients with boxers fractures secondary to aggressive actions were analysed and the 2D:4D ratio was calculated. A further 150 X-rays from patients not involved in aggressive activities were used as a control group and the 2D:4D ratio was calculated in the same manner. We then performed statistical analysis to compare the 2D:4D ratios between our two groups. ResultsAs predicted, the 2D:4D in males was smaller than females in all of the groups. However, our results showed that those presenting with a boxers fracture due to an aggression related injury had a statistically significant smaller 2D:4D ratio when compared to the normal population. ConclusionBoxers fractures are injuries that typically occur from an aggressive act. It is well documented that a low 2D:4D ratio is reflective of an increased prenatal exposure to androgens, particularly testosterone. We have shown that boxers fractures are associated with a smaller 2D:4D ratio than the normal population, thus suggesting that persons exposed to high levels of prenatal androgens are more likely to exhibit aggressive tendencies in adulthood. Our results suggest that smaller digit ratios may predict a predisposition to acts of aggression, and as such result in an increased likelihood of sustaining an injury such as a boxers fracture. This relationship seems to be present independently of gender.

2D:4D finger length ratio and reproductive indices in a Chuvashian population

to evaluate the association between 2D:4D finger length ratios (representing the prenatal environment, i.e., early androgen exposure) and reproductive indices, such as age at menarche, menopausal age, and length of reproductive period. Retrospective data on age at menarche and menopausal age as well as x-rays of both hands were obtained from 674 Chuvashian women aged 18-70 years (mean 46.32 ± 15.42). Finger and metacarpal length ratios as well as visual classification of finger ratio types, were estimated from the x-rays. We found that a low 2D:4D ratio (radiologically evaluated), a masculine 2D:4D ratio type (visually evaluated), and a putative bioassay for prenatal androgen exposure, were associated with a later menarche and a shorter reproductive period. No association was found with menopausal age.

Sex Determination using Finger Length, Fingers Ratio, and Foot Dimensions in Fayoum Governorate

The determination of sex is statically the most important criterion in identification of identity as it excludes approximately half the population at risk. Sex assessment is one of the first essential steps in human identification, in both medico-legal cases and bio-archaeological contexts. Fragmentary human remains compromised by different types of inhumation or physical insults may frustrate the use of the traditional sex estimation methods, such as the analysis of the skull and pelvis. Currently, the application of discriminate functions to sex unidentified skeletal remains is steadily increasing. Human population exhibit some degree of sexual dimorphism which help sexual discrimination such that the male skeleton are on average larger than female thus allowing the size of skeleton to be used to estimate sex. The length of fingers and foot dimensions can determine the possibility of sexual dimorphism in addition to the interdigital ratios that do not depend on the body size, height, or age. Anthropometric measurements of the hand and foot dimensions (length and breadth) now become very important tool in sexual dimorphism detection in addition to the length of the small bone of the hand. This study aims to use of various parameters (length of the hand fingers and hand bone length, ratio between fingers) and foot dimensions ( length and breadth) in determination of the sex of individuals via the use of statistical analysis study was conducted on 200 Egyptian volunteer randomly selected adult 20-35 years old(100 male and 100 female), from Fayoum city. All subjects were healthy , had no fracture or disease .The mean age of the studied group of male volunteers is 21.40 years while that of female is 22.37 years old. The length of the fingers of males measured using a spreading caliber (the thumb is excluded) each finger given a number 2F, 3F, 4F, 5F for index ,middle ,ring and little finger respectively, same is done for the female. The finger length is the distance between the tips of the finger till proximal flexion crease of that finger. The ratio between fingers is measured and named after with sex possibility (2f/3f, 2f/4f, 2f/5f, 3f, 4f, 3f/5f, 4f/5f) .The results are analyzed statistically using SPSS program calculating the mean ,S.D and S.E. T test is used to compare different finger length ratio between fingers, and foot dimensions, and the p value is calculated. The results prove that the mean length of male fingers is more than that of female and the 2f/3f, 2f/4f, 2f/5f of the male and female right hand is highly significant less than0 .001 also 3f/4f. While regarding to foot dimensions, the mean value were larger in left foot than the right. The foot length was the measurement with the greatest sex difference in both feet. In both feet, the length was the most sensitive variable 93% with 98% accuracy in left foot and 83% in right foot. In all age groups, the foot index in female was found to be more than 36, and less than 36 in male. Therefore, this value 36 can be used as deviation point for the determination of sex; hence, we can use these variants as sex determinant.

Mental rotation in intellectually gifted boys is affected by the androgen receptor CAG repeat polymorphism

Testosterone was shown to organize brain and modulate cognitive functions. It is currently unknown whether mental rotation is also associated with prenatal testosterone exposure and testosterone-related genetic polymorphisms. The aim of our study was to analyze associations between mental rotation performance, the actual testosterone levels, the prenatal testosterone level (expressed as 2D:4D ratio) and the androgen receptor CAG repeat polymorphism in intellectually gifted boys. One hundred forty-seven boys aged 10–18 years with IQ>130 were enrolled. Saliva samples were collected and used for ELISA of actual levels of salivary testosterone. The 2D:4D finger length ratio as an indicator of prenatal testosterone was measured on both hands and averaged. Amthauer mental rotation test was used for the assessment of this spatial ability. The CAG repeat polymorphism in the androgen receptor gene was analyzed using PCR and capillary electrophoresis. Linear regression revealed that 2D:4D finger length ratio and the number of CAG repeats in the androgen receptor gene were associated with mental rotation. Actual levels of testosterone did not correlate significantly with mental rotation. Multivariate analysis of covariance revealed that after adjustment of age as a confounding variable, only the effect of the genetic polymorphism was significant. The results are in line with our previous genetic analysis of intellectually gifted boys showing the importance of CAG repeat polymorphism in the androgen receptor gene. Details of the interactions between androgen signaling, testosterone levels and its metabolism especially during the prenatal development of brain function remain to be elucidated.

2D:4D finger length ratio in the Chuvashian population

In a sample of Chuvashians (803 males and 738 females) we evaluated the mean values of index finger to ring finger (2D:4D) ratio, the contributions of phalanges and metacarpals to the 2D:4D ratio, and the symmetry between right and left 2D:4D ratios.Age, sex, anthropometric data and radiographs of both hands were collected. Each hand was visually classified on a radiograph as either Type 1 – index finger was longer than ring finger; Type 2 – equal; or Type 3 – index shorter than the ring finger. The following measurements (1) from the mid-point of the base of the proximal phalanx to the mid-point of the tip of the distal phalanx; and (2) from the mid-point of the base to the mid-point of the tip of the metacarpal were obtained from the index and ring fingers.Visual classification was significantly associated with the measured 2D:4D length ratio. Women had a higher prevalence of Type 1 and Type 2, but lower prevalence of Type 3 ratio in both hands. Men had smaller measured 2D:4D phalangeal, metacarpal and ray (combined) ratios than women.Symmetry between the right and left hand measured 2D:4D ratios were significant in phalangeal (r=0.657, p<0.001), metacarpal (r=0.638, p<0.001), ray (r=0.682, p<0.001) ratios and visual classification types (contingency coefficient=0.559, p<0.001). No sex dimorphism was found between the right and left hands.Correlations between age and visual classification were significant on both sides before and after adjustment for sex. This result is probably a sign of a secular trend in the Chuvashian sample and the study should be replicated in other samples.

Update on the Biology of Transgender Identity

Numerous studies have attempted to isolate biological factors in the development of transgender identities through research into genetics, prenatal hormone exposure, neuroanatomy, and cognitive processing. Genetic studies demonstrate that chromosomal variations are uncommon but may occur at higher rates than in the general population. Candidate genes have been investigated, with some positive results, though these have yet to be replicated. Investigations into the effects of hormone exposure on the developing fetus have focused on gender identity in intersex people, which is often unpredictable, and proxy markers for prenatal hormone exposure such as finger length ratio and birth order, which do not show clear trends in transgender groups. A few small neuroanatomical studies show distinctions in transgender people, but results are limited in their scope due to small sample sizes and confounding variables such as adult hormone exposure. Numerous studies demonstrate that male-to-female (MTF) transgender people have higher rates of left-handedness, but the theoretical basis for this difference is not well described. Accumulating evidence indicates that prenatal biology likely contributes to transgender identity, but that its role may be interactive, rather than deterministic.

Revisiting Geschwind's hypothesis on brain lateralisation: A functional MRI study of digit ratio (2D:4D) and sex interaction effects on spatial working memory

The Geschwind-Behan-Galaburda (GBG) hypothesis links cerebral lateralisation with prenatal testosterone exposure. Digit ratio measures in adults have been established as potential markers of foetal sex hormonal milieu. The aim of the study was to evaluate the sex-dependent interaction of digit ratio measures and cerebral lateralization as well as their neurohemodynamic correlates using functional MRI (fMRI). Digit ratio measures—ratio of index finger (2D) length to ring finger (4D) length (2D:4D) and difference between 2D:4D of two hands, i.e., right minus left (DR–L)—were calculated using high resolution digital images in 70 right-handed participants (42 men) based on reliable and valid method. fMRI was acquired during the performance of a spatial working memory task in a subset of 25 individuals (14 men), and analysed using Statistical Parametric Mapping 8 (SPM8) and the Laterality Index toolbox for SPM8. Men had significantly less bilateral 2D:4D than women. There was a significant negative correlation between right 2D:4D and 2-Back task accuracy (2BACC) in women. A significant sex-by-right 2D:4D interaction was observed in left parahippocampal gyrus activation. Additionally, sex-by-DR–L interaction was observed in left IPL activation. DR–L showed a significant positive correlation with the whole brain Laterality Index (LI), and LI, in turn, demonstrated a significant negative correlation with 2BACC. Our study observations suggest several novel sex-differential relationships between 2D:4D measures and fMRI activation during spatial working memory task performance. Given the pre-existing background data supporting digit ratio measures as putative indicator of prenatal sex hormonal milieu, our study findings add support to the Geschwind-Behan-Galaburda (GBG) hypothesis.

Review Article: Studies of Human Sex Ratios at Birth May Lead to the Understanding of Several Forms of Pathology

This article deals with the problem of the causes of the variation of sex ratio (proportion male) at birth. This problem is common to a number of areas in biology and medicine, for example, obstetrics, neurology/psychiatry, parasitology, virology, oncology, and teratology. It is established that there are signifi cantly biased, but unexplained, sex ratios in each of these fi elds. Yet workers in them (with the possible exception of virology) have regarded the problem as a minor loose end, irrelevant to the fi eld's major problems. How- ever, as far as I know, no one has previously noted that unexplained biased sex ratios occur, and thus pose (perhaps similar) problems, in all these fi elds. Here it is suggested that similar sorts of solutions apply in each. Further research is proposed for testing each solution. If the argument here is substantially correct across this range of topics, it may lead to an improved understanding not only of sex ratio but also of some of the pathologies in these specialties. Sexual reproduction is a phenomenon that is central to biology; moreover, there is substantial variation in the sex ratio at birth. Yet the causes of this variation are not established, and some infl uential commentators (e.g., Wilcox 2010) are skeptical about present prospects for progress in this area of human reproduction. This review adduces data on several forms of variation of human sex ratio at birth: those associated with autism, hepatitis B, toxoplasmosis, testicular cancer, Manning's fi nger length ratio 2D:4D, and some obstetric pathologies and congenital malformations. My intention is to argue that each of these forms of sex ratio varia- tion presents a problem to which I may have provided a general solution. However, though I may propose, I am not qualifi ed to test, potential mechanisms for this solution. Instead, I suggest that specialists in each of these pathologies might be

The Ratio of Second to Fourth Digit Length (2D:4D) and Coronary Artery Disease in a Han Chinese Population

Background: The association between index finger to ring finger length ratio (2D:4D) and cardiac disorders has been reported, however it has not been discussed in terms of coronary artery disease (CAD). We investigated whether 2D:4D could be used as a marker for predisposition to CAD as assessed by coronary angiography in Chinese men and women.Methods: This study included 1764 persons divided into 4 groups, 441 cases with CAD and 441 persons without CAD as control in each sex of the same age. Finger lengths were measured twice for both hands using electronic calipers. Student t test was used to detect the difference of 2D:4D among groups. The receiver operator characteristic curves (ROCs) were used to detect the diagnostic effect of 2D:4D for CAD.Results: There were no significant differences in age among the four groups. A significant difference of 2D:4D ratios between right and left hand were observed only in men in both control and CAD groups. On the right hand in the control group and on both hands in the CAD group, the 2D:4D ratios were higher in women than in men (all, P < 0.001). In men with CAD, mean 2D:4D was higher than mean 2D:4D in control men (right hand 0.962±0.042:0.927±0.038; left hand 0.950±0.044:0.934±0.048; both hands, P < 0.001), but this was not observed in women. No relationship was found between 2D:4D and age (all, P >0.05). The area under the curve of right hand 2D:4D in male was 0.72 (95% CI 0.683-0.753, p<0.001), while it was 0.602 (95% CI 0.565-0.639, p<0.001) in left hand.Conclusions: The present study showed an association between high 2D:4D ratio and CAD in both hands in men. There were no significant differences in mean 2D:4D between women with CAD and controls.

손가락 비율을 이용한 장애인 특성

태아기의 성 호르몬의 차이가 두 번째 손가락과 네 번째 손가락 길이의 비율을 비롯하여 여러가지 생리적 특성에 영향을 미칠 수 있다는 연구가 발표된 이후 관련 연구가 많이 진행되어 오고 있다. 그러나 우리나라 장애인을 대상으로 한 연구는 드물다. 이에 본 연구에서는 우리나라 장애인과 일반학생을 대상으로 손가락 비율 비교 및 장애인의 특성을 실증적으로 분석해 보았다. 그 결과, 장애인과 일반학생 모두에 있어 남자의 손가락 검지와 약지 길이 비율이 여자보다 낮아, 남녀별 성차가 있다는 일반적 사실을 확인 할 수 있었다. 다음으로, 남자와 여자 장애인 모두에서 나이대별 손가락 길이 비율은 통계적으로 유의한 차이가 없는 것으로 나타나, 일반인과 마찬가지로 장애인도 성장과정에서 검지와 약지 길이 비율이 크게 변하지 않음을 알 수 있었다. 마지막으로, 남자와 여자 지적 장애인 모두에 대하여 장애등급별 손가락 길이 비율도 통계적으로 유의하지 않은 것으로 나타난 바, 이로부터 손가락 검지와 약지 길이 비율이 장애여부와 관계가 있다는 점에 근거하면 현재의 장애등급 구분은 문제가 있다고 하겠다. Recent research has been mostly focused on the differences of prenatal sex hormone could affect the ratio of the lengths of the second to fourth digits (2D:4D) as well as the rate of several physiological characteristics. It has been suggested that digit ratios are thought to be associated with either higher prenatal testosterone levels or greater sensitivity to androgens, or both. However, a study of person with disabilities are rare in Korea. The purpose of this study was to compare patterns of the ratio (2D:4D) of the lengths of the second and fourth digits in persons with disabilities and students without disabilities. Also, we empirically analyze the characteristics of persons with disabilities. We found that finger length ratio (2D:4D) of men with disabilities and student without disabilities were lower than women with disabilities and student without disabilities. Therefore, it could be confirmed that finger length ratio (2D:4D) is sexually dimorphic trait. There were no correlations between finger length ratio (2D:4D) and age group in persons with disabilities. Therefore, as with person without disabilities, the 2D:4D ratio was negatively associated with a growth process of persons with disabilities. Finally, There was no difference correlations between finger length ratio (2D:4D) and level of disability in persons with intellectual disabilities. From this, one possible explanation for this is that if finger length ratio (2D:4D) is related to person with disability then current classification of the level of disability deserves further investigation.

The Relationship Between Second‐to‐Fourth Digit Ratio and Female Gender Identity

Gender identity and the second-to-fourth finger length ratio (2D : 4D) are discriminative between the sexes. However, the relationship between 2D : 4D and gender identity disorder (GID) is still controversial. The aim of this study is to investigate the relationship between 2D : 4D and score on the Gender Identity Scale (GIS) in female-to-male (FtM) GID subjects. Thirty-seven GID-FtM with testosterone replacement therapy from our clinic were included in this study. As controls, 20 male and 20 female volunteers participated from our institution (medical doctors and nurses). We photocopied left and right hands of the participants and measured the second and fourth finger lengths. Gender identity was measured with the GIS. 2D : 4D digit ratio and GIS in male, female, and GID-FtM subjects. The 2D : 4D (mean ± standard deviation) in male, female, and GID-FtM were 0.945 ± 0.029, 0.999 ± 0.035, and 0.955 ± 0.029 in right hand and 0.941 ± 0.024, 0.979 ± 0.040, and 0.954 ± 0.036 in left hand, respectively. The 2D : 4D was significantly lower in male controls in both hands and GID-FtM in the right hand than in female controls (P < 0.05, analysis of variance). Multiple linear regression analysis revealed that "consistent gender identity" score in the higher domain in GIS and "persistent gender identity" score in the lower domain are statistically significant variables correlating with 2D : 4D in the right hands among biological females. The finger length ratio 2D : 4D in GID-FtM was significantly lower than in female controls in the right hand in this study. 2D : 4D showed a positive correlation with GIS score. Because 2D : 4D influences are assumed to be established in early life and to reflect testosterone exposure, our results suggest a relationship between GID-FtM and perinatal testosterone.