Digit Ratio Research Articles

Endocrine effect of phthalate metabolites and a butterfly effect of prenatal exposure to androgens on qualitative aspects of female sexual response- an initial survey.

There is growing evidence that endocrine disruptive chemicals have deleterious effects on sexual and reproductive function. To examine subjective sexual functions in human females and their relationship to postnatal phthalate exposure and perinatal androgenization, a Sexuality Score (SS) was established from a first-stage survey questionnaire of subjective sexual function filled out by female university students (n = 68; average age 25.23 ± 5.17 years; rural 25.51 ± 6.74 vs. urban 25.85 ± 1.43 years). Seventeen phthalate metabolites in urine samples were analyzed by high-performance liquid chromatography (HPLC) and tandem mass spectrometry (MS/MS). Females were also assessed for the 2D:4D digit ratio as an index of perinatal androgenization. The mean age of menarche was 12.82 ± 1.35 years (rural 12.59 ± 1.39 vs. urban 13.18 ± 1.27; p = 0.01). The mean age at first sexual intercourse was 14.88 ± 6.89 years (rural 14.62 ± 7.20 vs. urban 15.24 ± 6.55), and as the age of first sexual intercourse increases, the SS score tends to increase as well, albeit moderately (r = 0.25, p = 0.037). Mono-iso-butyl phthalate, mono(2-ethyl-5-carboxypentyl) phthalate, mono(hydroxy-n-butyl) phthalate, mono(2-ethyl-5-oxohexyl) phthalate (p ≤ 0.05) and mono(2-carboxymethylhexyl) phthalate (p ≤ 0.01) were negatively associated with SS. A compounding butterfly effect of prenatal exposure to androgens was observed with disruptive effects of mono(2-ethyl-5-oxohexyl) phthalate and mono(2-ethyl-5-carboxypentyl) phthalate on sexual function. Exposure to phthalates in adult females may lead to disruption of subjective sexual function, especially concerning sexual desire and sexual satisfaction, and perinatal androgenization could augment these effects.

Digit Ratio (2D:4D): A Contributor to Trustworthiness Among Africans

Studies conducted on Caucasian subjects have shown a link between increased testosterone levels and an increase in interpersonal betrayal behaviors as well as a reduction in the 2D:4D ratio. It's unclear, however, whether this holds for tribes in Africa. Although 2D:4D may be used as a measure of exposure to prenatal testosterone, it is important to recognize that this association is limited to those who identify as Caucasian. The present study aims to determine the association of the 2D:4D ratio with trustworthiness in the African population. Four hundred and two (402) people were selected at random from two organizations in the Kano state. Both TOAKAN and the Tsaya da Kafarka Taxi Drivers Association are involved in this matter. Participating individuals' ages varied from eighteen to fifty (18-50). A direct method of measuring was used to approximate the lengths of the second and fourth digits. To further assess how trustworthy people perceive one another, a 45-question trustworthiness questionnaire (TQ) was also created. The mean value of 2D: 4DR was 0.98±0.04 which was higher than 2D: 4DL with a mean value of 0.96±0.05. Two components of the dependability scale, 2D: 4DRight(R), Total trustworthiness, and Consistency, were shown to have a positive and statistically significant relationship. On the other hand, no association was found between the 2D:4DLeft (L) and any of the dependability metrics.

Second to fourth digit ratio (2D:4D) as the 'anatomical marker' and reproductive 'hormonal fingerprint' in the occurrence dental plaque accumulation.

Digit ratio (2D:4D), as endocrine fingerprint, can indicate prenatal androgen exposure. It serves as an anatomical marker for various systemic diseases and a few studies relating it to oral health. The present study aims to evaluate the association between digit ratio and susceptibility to dental plaque formation. The study was conducted on young adults aged between 18 and 25 years. Digit ratio and reproductive hormones were measured; dental plaque score and gingival index (GI) were recorded. Data were analysed using the MedCalc. v.20. Male and female participants were categorized into two groups based on their digit ratios being either above or below the calculated average (0.99 for females, 0.98 for males). Those with a digit ratio below the average had a significantly higher mean dental plaque score (p < 0.0001) than those with ratios at or above the average. However, there was no significant difference in the GI between the two groups. Reproductive hormone profiles varied significantly between the higher and lower digit ratio groups for both sexes. Digit ratio may find potential to be used as an anatomical marker to identify the susceptibility to dental plaque build-up.

2D/4D Finger Length Ratio in the Screening of Developmental Dysplasia of the Hip.

To investigate whether there is a relationship between the 2nd finger and 4th finger length measurement ratios and developmental dysplasia of the Hip (DDH). Cross-sectional observational study. Place and Duration of the Study:Department of Orthopaedics and Traumatology, Meram Faculty of Medicine Hospital, Konya, Turkiye, from January 2020 to May 2023. Infants were screened for DDH with Graff method for the ultrasounds of both hips. Lengths of the 2nd and 4th fingers of both hands were measured and recorded. Patients with additional risk factors for developmental dysplasia of the hip (breech birth, family history, oligohydramnios, swaddling) were excluded. Two hundred and fifty-six babies were screened including 55.1% (n = 141) girls and 44.9% (n = 115) boys. Their mean age was 2.51 ± 0.80 months. The average lengths were 31.73 ± 3.05 mm, for the left 2nd finger and 34.26 ± 3.48 mm for the left 4th finger. In the hip USG measurements, the mean alpha angles were 62.91 ± 3.12° for the right hip and, 63.20 ± 3.55° for the left hip. Eighteen (7%) of babies who underwent hip ultrasound (USG) had unilateral or bilateral DDH. Among these cases, 2.7% (n = 7) had right, 2.3% (n = 6) had left, and 2% (n = 5) had bilateral DDH. There was no statistically significant correlation between the ratios of right 2/4 finger lengths and the right alpha angle (rs = 0.051; p = 0.421). There was a statistically positive and statistically significant correlation between the ratios of left 2/4 finger lengths and the left alpha angle (rs = 0.154; p = 0.013). Only the left-hand finger ratio among the parameters in the model had a statistically significant effect on DDH. Therefore, the left hand 2D/4D finger length may be of value in screening for DDH. Developmental dysplasia of the hip, Second to fourth finger digit ratio, Ring finger, Digit ratios.

The change in handgrip strength, after physical exercise, is moderated by digit ratio (2D:4D): A study among the young adults in Poland.

The digit ratio (2D:4D), the ratio of the lengths of second (2D) to the fourth (4D) fingers, is a proxy indicator of prenatal androgen exposure. On average, males display lower 2D:4D than females. Previous studies have shown that lower 2D:4D ratios were associated with better sports and physical abilities. To assess whether a challenge condition, imposed by intense exercise, could increase handgrip strength (HGS) associated with 2D:4D. This cross-sectional experimental study included 90 healthy young Polish adults (40 males, 50 females). They underwent intense physical exercise, before (7 days) and after which they were measured for HGS and 2D:4D. Height and weight were also measured. Analyses of Covariance were employed to delineate associations. 2D:4D had significant predictive effects on the differences in HGS (DHGS) measured in two occasions, without and after, physical exercises. The lower was the 2D:4D, the higher the DHGS, particularly, for the left hand. The results reconfirmed that the link between prenatal testosterone exposure (indicated by 2D:4D) and physical strength depends on the context, such as a challenged condition.

The association and underlying mechanism of the digit ratio (2D:4D) in hypospadias.

The second-to-fourth digit (2D:4D) ratio is thought to be associated with prenatal androgen exposure. However, the relationship between the 2D:4D ratio and hypospadias is poorly understood, and its molecular mechanism is not clear. In this study, by analyzing the hand digit length of 142 boys with hypospadias (23 distal, 68 middle, and 51 proximal) and 196 controls enrolled in Shanghai Children's Hospital (Shanghai, China) from December 2020 to December 2021, we found that the 2D:4D ratio was significantly increased in boys with hypospadias ( P < 0.001) and it was positively correlated with the severity of the hypospadias. This was further verified by the comparison of control mice and prenatal low testosterone mice model obtained by knocking out the risk gene (dynein axonemal heavy chain 8 [ DNAH8 ]) associated with hypospadias. Furthermore, the discrepancy was mainly caused by a shift in 4D. Proteomic characterization of a mouse model validated that low testosterone levels during pregnancy can impair the growth and development of 4D. Comprehensive mechanistic explorations revealed that during the androgen-sensitive window, the downregulation of the androgen receptor (AR) caused by low testosterone levels, as well as the suppressed expression of chondrocyte proliferation-related genes such as Wnt family member 5a ( Wnt5a ), Wnt5b , Smad family member 2 ( Smad2 ), and Smad3 ; mitochondrial function-related genes in cartilage such as AMP-activated protein kinase ( AMPK ) and nuclear respiratory factor 1 ( Nrf-1 ); and vascular development-related genes such as myosin light chain ( MLC ), notch receptor 3 ( Notch3 ), and sphingosine kinase 1 ( Sphk1 ), are responsible for the limitation of 4D growth, which results in a higher 2D:4D ratio in boys with hypospadias via decreased endochondral ossification. This study indicates that the ratio of 2D:4D is a risk marker of hypospadias and provides a potential molecular mechanism.

Is digit ratio (2D:4D) a biomarker for lactate? Evidence from a cardiopulmonary test on professional male footballers

BackgroundLactate accumulation is associated with vigorous exercise, cardiovascular disease and a number of cancers. Digit ratio (2D:4D) has also been linked to oxygen metabolism, myocardial infarction and various cancers. Such similarities suggest the possibility that 2D:4D is a biomarker of lactate. Here, we consider the relationship between 2D:4D and lactate during an incremental cardiopulmonary exercise test. MethodThe participants were male professional football players. The treadmill test began at a speed of 8 km/h when the first lactate measurement was taken. The speed was increased by 2 km/h every 3.15 min, with measurements at 10, 12, 14 and 16 km/h. ResultsThere were 72 Caucasian and 7 Black participants, results are reported for the most numerous group. Lactate levels increased with running speed and were not correlated with age, body size or body composition. Median splits of digit ratios (right, left and right-left 2D:4D [Dr-l]) were calculated. In comparison to the Low ratio group, the High ratio group showed higher lactate levels across speeds. Effect sizes varied from very large to huge (right 2D:4D), large (left 2D:4D) and medium (Dr-l). At the individual level, positive correlations between digit ratios and lactate at the five different speeds varied from large (right 2D:4D), medium (left 2D:4D) and small (Dr-l). ConclusionThere were large positive associations between right 2D:4D and lactate at all running speeds. We discuss our findings in relation to oxygen metabolism and suggest that 2D:4D may be a biomarker for lactate in the wider context of the latter's importance in health and disease.

The Relationship of 2D:4D Finger Length Ratio with Biomotoric Characteristics and Sports Performance in Adolescent Basketball Players

Background. The aim of this study is to determine the relationship of 2D:4D finger length ratio (also known as digit ratio) with biomotoric features and sports performance in adolescent basketball players. 24 male basketball players with a mean age of 14.83±0.71 years and a training age of 7.08±1.92 years participated in the study. Materials and methods. The participants’ 2D and 4D finger lengths of both hands, height (cm), body weight (kg), some biomotoric characteristics and sports performances were determined by measurements. The German Heidelberger Basketball Test was conducted to evaluate the basketball-based sports performances of the participants. The SPSS 25.0 package program was performed in the statistical analysis of the obtained data. The Shapiro-Wilk test was used to determine whether or not the data showed a normal distribution. Parametric tests were preferred for statistical analysis as the data were found to have a normal distribution. Results. It was found that there was no statistically significant relationship between the 2D:4D finger length ratio, some motoric features and basketball-based sports performances of the participants (p&gt;0.05). It was concluded that the ratio of 2D:4D finger lengths in adolescent basketball players did not have an effect on biomotoric features and basketball-based sports performance. When the correlation between 2D:4D finger length ratio and sports performance parameters was examined, no statistically significant relationship was observed (p&gt;0.05). Conclusions. Although some studies show a significant negative correlation between performance tests and the 2D:4D ratio, it should be noted that the 2D:4D finger ratio is not the only determinant for sports performance.

Association between the digit ratio (2D:4D), handgrip strength, wrist ratio, and body fat distribution in women with different carpal tunnel syndrome severity

BackgroundTo evaluate the relationship of the second to fourth digit ratio (2D:4D), a biomarker of prenatal sex hormone exposure, with wrist ratio (WR), wrist-palm ratio (WPR), body mass index (BMI), waist-hip ratio (WHR), and handgrip strength (HGS) in different carpal tunnel syndrome (CTS) severity. MethodThis study involved 90 female participants (aged 18 to 83) with CTS. According to CTS severity, the participants were divided into four groups: normal, mild, moderate, and severe. All parameters of hand anthropometry and body fat distribution were measured, and the mean 2D:4D, WR, WPR, HGS, BMI, and WHR values were compared based on CTS severity. Data were collected with a visual analog scale (VAS) for pain and a Likert (LS) scale for numbness severity. ResultsThe mean age, 2D:4D, WD, WW, WR, WPR, BMI, and HGS values showed a significant differences between CTS severity groups. We found that lower 2D:4D and higher WPR and BMI were associated with increased risk of CTS (AUC = 0.728) after removing the effect of age. Bilateral hands were affected in 38.9 % (70/180) of participants. Regression analysis showed that lower HGS can be used as independent variable for predicting the females having bilateral affected hands. The LS score was considerably higher in the severe and moderate groups. Also, the VAS score was significantly higher in the severe group. ConclusionThe findings of the study demonstrated an association between 2D:4D, WPR, and BMI among women, emphasizing the effect of intrauterine sex hormone exposure on late life CTS severity.

The associations between digit ratio (2D:4D and right - left 2D:4D), maximal oxygen consumption and ventilatory thresholds in professional male football players.

Digit ratio (2D:4D: the relative length of the 2nd and 4th digit) is thought to be a negative correlate of prenatal testosterone. The 2D:4D is related to oxygen metabolism, but the precise nature of this relationship is unclear. The purpose of the present study was to consider associations between digit ratios (right 2D:4D, left 2D:4D, right-left 2D:4D [Dr-l]) and VO2max and ventilatory thresholds (VT1 and VT2). One hundred and thirty-three Caucasian (n = 133) professional football players competing in Cyprus participated in the study. Players underwent anthropometric measurements, and digit lengths were measured from hand scans. They also completed an incremental cardiopulmonary test to exhaustion on a treadmill. There were negative correlations between digit ratios and VO2max (right 2D:4D, r = -.65; left 2D:4D r = -.37, both p < .0001; Dr-l r = -.30, p = .0005). There were no relationships between digit ratios and VT1. For VT2, there were negative relationships with digit ratios (right 2D:4D, r = -.43, p < .0001; left 2D:4D, r = -.21 and Dr-l, r = -.21, both p = .02). Digit ratios are negatively related to VO2max with large (right 2D:4D) and medium (left 2D:4D, Dr-l) effect sizes. For VT2, there were also negative correlations, which were medium (right 2D:4D) and small (left 2D:4D, Dr-l). Our findings may help clarify the relationships between digit ratios and high-intensity actions for extended periods, which are dependent on efficient oxygen metabolism.

Understanding Covid-19: Digit ratios and duration of oxygen therapy in hospitalized Covid-19 patients

BackgroundCovid-19 severity shows a sex difference (males>females) and progressive hypoxia among the most seriously affected. Digit ratios are sexually dimorphic and may be negatively-related to prenatal (2nd-to-4th digits' ratio; 2D:4D) and pubertal (3rd-to-5th digits' ratio; 3D:5D) testosterone. Oxygen therapy is important in Covid-19 treatment and low 2D:4D is linked to efficient oxygen metabolism. We consider relationships between digit ratios and duration of oxygen treatment in hospitalized Covid-19 patients. MethodsDigit lengths were measured from photographs of the patient's hands. Age, Sex, BMI, vaccination status and number of days of O2 treatment, were recorded. ResultsThere were 100 (58 women) patients. Sex differences (males<females) were present in 2D:4D ratios (Dr-l 2D:4D; ǀDr-l 2D:4Dǀ) but not in 3D:5D. Positive relationships were found between 2D:4D variables (left 2D:4D, women and men; Dr-l 2D:4D women), 3D:5D (male left 3D:5D) and duration of oxygen therapy. After removal of the influence of age, BMI, vaccination status and sex there were positive relationships between 2D:4D (right and left) and duration of oxygen therapy but no such associations for 3D:5D. In addition to 2D:4D there was evidence for a positive relationship between BMI and oxygen therapy. ConclusionWe have found that high (feminized) 2D:4D of males and females is positively related to duration of oxygen therapy. This adds to the evidence for links between severity of Covid-19 and national and individual level variation in foetal androgen (as measured by 2D:4D). We discuss our finding in the light of the “low-androgen-driven COVID-19 pandemic theory”.

No correlation between sexually dimorphic ratios of the sizes of fourth to second digits and hypothesized ratios of the sizes of the central to lateral incisors

Abstract Aim: Following the fourth to second digit ratios being used as a marker of sexual dimorphism and the embryogenetic hormonal origin in common with the permanent dentition, the aim of this study was to determine if a homologous ratio existed for the central and lateral incisors which correlated with the digit ratios. Materials and Methods: Bilateral linear lengths in millimeters of fourth and second digits (reversed for clearer analysis) were obtained using vernier calipers from standardized photocopies of the ventral palmar surfaces of 61 male and 51 female (n = 112) volunteer dental students, the ratios of which were correlated with the ratios of the linear measures (mm) of the inciso-cervical (IC) and mesiodistal (MD) measurements of their central to lateral incisors. Results: Dimorphic digit ratios were comparable with those of other investigators, with male digits and incisors significantly larger than females (p &lt; .001). Although both male maxillary incisors, IC and MD, were significantly larger than females, the ratios unexpectedly were not, with only a limited number of low but significant correlations with the digit ratios. Conclusions: While there were only a limited number of significant sexually dimorphic correlations between the digit and incisor ratios for non-White participants, the results obtained suggest further investigation of possible relationships between the sexually dimorphic digit ratios and odontometric ratios other than central to lateral incisors.

The age difference in 2D:4D among the Polish population: An exploratory study

In this study a widely debated association between 2D:4D digit ratio and age was investigated. The study material included 960 individuals (530 females and 430 males) from Central Poland aged between 6–79 years. The information about age was obtained via survey filled in by study participants or, if underaged, their parents. The direct measurements of the second and fourth finger were performed to assess the 2D:4D digit ratio. The 2D:4D digit ratios for the left hand were significantly correlated with age both among females and males. In women the 2D:4D digit ratios for the right hand were significantly correlated with age. There were also significant differences in digit ratio between age groups. The results of our study suggest that there might be an association between digit ratio and age, and the direction of the correlation might be related to the phase of the ontogenesis.

Establishing the Congruity amongst 2D:4D Ratio, Sex, and Socio-Behavioural Traits in Medical Students of Enugu State University of Science and Technology (ESUT)

The second-to-fourth digit (2D:4D) ratio is a sexually dimorphic trait that has previously been reported to be associated with socio-behavioral characteristics. This study examined the relationship amongst 2D:4D ratio, sex, and socio-behavioral characteristics among undergraduate medical students at Enugu State University of Science and Technology. A quantitative descriptive cross-sectional study design was adopted and a sample size of 120 was calculated using the Taro-Yamane formula. Convenience sampling method was utilized and the majority exhibited positive socio-behavioral characteristics such as emotional control and stress management abilities. There was a significant difference in the personality traits (conscientiousness and openness) between the male and female population at P&lt;0.050. However, there were no significant differences between the left and right digit ratio among the male and female population as P&gt;0.050 in each case. Also, there was no significant difference in the level of executive functions (emotional control, inhibition control, and stress intolerance) among the male and female populations as P&gt;0.050 in each case. There was a significant negative correlation between the right-hand 2D:4D digit ratio and level of conscientiousness among the population with (r=-0.196) at P&lt;0.050. However, no significant association was found between personality traits and executive functions. There was no significant difference between the participants’ digit ratio and gender. However, the male right-hand 2D:4D digit ratio was significantly associated with conscientiousness among the population. Additionally, no significant correlation was found between the participant’s digit ratios and their executive functions (emotional control, inhibition control, and stress tolerance).

Detecting children's dental caries risk through finger-digit ratio

Objective: This research aimed to determine whether fingerprints could be used to predict the risk of tooth decay.&#x0D; Material and Methods: A total of 157 children aged 6 to 12, were included in the study. Their 2D:4D digit ratio was measured using digital calipers. Additionally, intraoral examinations were conducted to assess their caries status using the DMF-T index.&#x0D; Results: a significant correlation between the digit ratio and the probability of dental caries in children aged 6-12 years at SD Inpres Panaikang. The statistical output shows a positive association between lower digit ratio values and an elevated risk of dental caries. The significance value of the analysis is 0.044, which is below the standard threshold of 0.05. &#x0D; Conclusion: There is a relationship between the digit ratio (2D: 4D) and the risk of dental caries. Hence, the digit ratio (2D: 4D) can be used to predict the occurrence of caries.

Digit ratio and the femoral circumflex artery perforator: A sex-dependent association between the vascular system of the thigh and prenatal sex hormones?

BackgroundThe anterolateral thigh flap (ALTF) is a type of free flap which is commonly used in reconstructive surgery procedures and is based on the perforator from femoral circumflex artery. Some authors found that the location of the perforator differs between sexes. ObjectiveTo verify the influence of prenatal sex hormones (as measured by 2D:4D) on the morphology of the perforator of the descending branch of the femoral circumflex artery. Methods88 participants (43 women) of a mean age of 28.5 years (SD 8.1 years) had the following measurements performed: height and weight; right and left-hand 2nd and 4th fingers' lengths; and distance from anterior superior iliac spine to the perforator from descending branch of lateral femoral circumflex artery related to the thigh length (right and left) (AP ratio). ResultsRight 2D:4D and Dr-l (right minus left 2D:4D) were dimorphic, similarly to AP ratio (right and left), which in women was significantly higher than in men. A significant correlation was found between right and left 2D:4D and location of the perforator of the left thigh in men. The higher right and left 2D:4D (more feminine) the higher the left AP ratio (more feminine). ConclusionOur findings suggest that the location of perforator of femoral circumflex artery may be influenced by prenatal sex steroids such that low prenatal testosterone and high prenatal oestrogen are correlated to high AP (lower branching of the artery).

Second and fourth (2D:4D) digit ratio in heroin and cannabis addicted patients

The etiology of addiction has not yet been fully elucidated. The ratio between the length of the second and fourth fingers (2D:4D ratio) has been linked with prenatal androgen concentrations, but also with addictive behvaiors. Aim: The present study aimed to evaluate the differences of 2D:4D ratio of individuals with cannabis and heroin addiction by examining them together with the control group. A total of sixty two male patients (33 opiate use disorder and 29 cannabis use disorder) with substance use disorder and the twenty-nine healthy controls were included in the present investigation. We obtained the lengths of 2D and 4D of the subjects by using sensitive calipers and calculated the 2D:4D. Heroin-addicted patients had lower 2D:4D ratio in in the right hand (significant difference between control group) (p < 0.001), there was no significant difference found between heroin-cannabis (p = 0.242) and control-cannabis 2D:4D ratios (p < 0.06). In the left hand, it was significant between the heroin-control groups (p < 0.037) and the cannabis-control groups (p < 0.023), while it was not significant between the heroin-cannabis groups (p = 1). In conclusion, we suggest that heroin-and cannabis addicted patients seem to have a lower ratio of 2D:4D compared to healthy control subjects. Our findings can be considered promising as to whether prenatal hormonal factors are important in the etiopathogenesis of addiction.

Association between Severe Early Childhood Caries, Dietary Preferences, and 2nd Digit-4th Digit (2D:4D) Ratio.

To evaluate the association between severe early childhood caries (S-ECC), dietary preferences, and 2nd digit-4th digit (2D:4D) ratio. The objective is to contrast the detection and prevalence of dental caries in children with different sensitivity levels to the bitter taste of 6-n-propylthiouracil (PROP) and its association with 2D:4D. A total of 300 children below 71 months of age were assigned to two study groups-group I (caries-free) and group II (caries). PROP sensitivity test was carried out to determine the inherent genetic ability to taste a bitter or sweet substance. Evaluation of dietary preferences was carried out using a food preference questionnaire, which was completed by the parents of the children to know the child's dietary habits and their sweet, sour, and strong taste preferences. The length of the index (2D) and ring (4D) finger was measured with the help of digital vernier caliper to record the 2D:4D ratio. The data obtained was subjected to statistical analysis using Pearson's Chi-squared test and one-way analysis of variance (ANOVA). The results suggested a positive association between S-ECC and dietary preferences but could not establish a straightforward 1:1 relation between 2D:4D ratio and S-ECC. An individual considered as nontaster by PROP test was a sweet liker with low 2D:4D ratio having high caries index. The association between 2D:4D ratio and S-ECC should further be explored by taking other influencing factors into consideration before arriving at a definitive conclusion. Srivastava SK, Garg N, Pathivada L, et al. Association between Severe Early Childhood Caries, Dietary Preferences, and 2nd Digit-4th Digit (2D:4D) Ratio. Int J Clin Pediatr Dent 2023;16(5):740-744.

The Use of 2D:4D Digit Ratio as a Predictor of Androgenetic Alopecia: A Review.

Androgenetic alopecia (AGA) is a widespread type of hair loss that affects both males and females. Advanced age and family history of AGA are well-established risk factors for developing AGA. The second to fourth digit ratio (2D:4D) is the ratio between the length of the index and ring fingers. This ratio has been utilized as a predictor for multiple hyperandrogenism-related medical conditions. More recently, 2D:4D was investigated as a predictor for AGA. This article aims to investigate the evidence supporting the use of 2D:4D as a predictor of AGA, and address areas of future research.

Digit Ratio (2D:4D; Right-Left 2D:4D) and Multiple Phenotypes for Same-Sex Attraction: The BBC Internet Study Revisited

Same-sex attraction may be linked to low prenatal androgen (in men) and high prenatal androgen (in women). Digit ratio (2D:4D) is thought to be a negative correlate of prenatal androgen and right-left 2D:4D (Dr-l) to reflect lateralized differences in sensitivity to prenatal androgen. Lower 2D:4D has been reported for lesbians compared to heterosexuals, but links to high 2D:4D in gay men are less clear. The largest study thus far (the BBC Internet study) found no significant difference between the 2D:4D of lesbians and heterosexual women but a higher 2D:4D in gay men compared to heterosexual men. Here we consider the possibility that low and high prenatal androgen is associated with same-sex attraction in men (n = 108,779) and women (n = 87,742), resulting in more than two phenotypes. We examined the associations between 2D:4D, Dr-l, and same-sex attraction scores in the BBC Internet study. In contrast to the earlier report, which considered sexual orientation in categories, there were positive linear associations in men (right and left 2D:4D, but not Dr-l) and negative linear associations in women (right 2D:4D and Dr-l, but not left 2D:4D). There were no curvilinear relationships for right and left 2D:4D. However, Dr-l showed a U-shaped association with same-sex attraction in men. Thus, (1) high prenatal androgen may be implicated in female homosexuality, while both low and high prenatal androgen may be implicated in male homosexuality, and (2) large side differences in sensitivity to androgen may be associated with elevated same-sex attraction in men.