Prenatal sex hormone effects on child and adult sex-typed behavior: methods and findings

Association between prenatal exposure to alkylphenols and intelligence quotient among preschool children: sex-specific effects

BACKGROUND

While prenatal exposure to alkylphenols (APs) has been demonstrated to be associated with neurodevelopmental impairments in animals, the evidence from epidemiological studies remains limited and inconclusive. This study aimed to explore the link between AP exposure during pregnancy and the intelligence quotient (IQ) of preschool children.

METHODS

A total of 221 mother-child pairs from the Guangxi Zhuang Birth Cohort were recruited. Nonylphenol (NP), 4-tert-octylphenol (4-T-OP), 4-n-nonylphenol (4-N-NP), and 4-n-octylphenol were measured in maternal serum in early pregnancy. Childhood IQ was evaluated by the Fourth Edition of Wechsler Preschool and Primary Scale of the Intelligence at 3 to 6 years of age. The impact of APs on childhood IQ were evaluated by generalized linear models (GLMs), restricted cubic spline (RCS), and Bayesian kernel machine regression (BKMR).

RESULTS

In GLMs, prenatal exposure to NP and the second tertile of 4-T-OP exhibited an inverse association with full-scale IQ (FSIQ) (β = -2.38; 95% CI: -4.59, -0.16) and working memory index (WMI) (β = -5.24; 95% CI: -9.58, -0.89), respectively. Prenatal exposure to the third tertile of 4-N-NP showed a positive association with the fluid reasoning index (β = 4.95; 95% CI: 1.14, 8.77) in total children, as well as in girls when stratified by sex. A U-shaped relationship between maternal 4-T-OP and WMI was noted in total children and girls by RCS (all P nonlinear < 0.05). The combined effect primarily driven by NP, of maternal AP mixtures at concentrations above the 50th percentile exhibited an inverse trend on FSIQ in total children and girls in BKMR.

CONCLUSIONS

Prenatal exposure to various APs affects IQ in preschool children, and there may be nonmonotonic and sex-specific effects. Further investigation across the population is required to elucidate the potential neurotoxic effects of APs.

Relationship between the 2D:4D and prenatal testosterone, adult level testosterone, and testosterone change: Meta-analysis of 54 studies

The ratio between the hands' second to the fourth finger (2D:4D) is commonly hypothesized to result from prenatal testosterone. The 2D:4D has also been hypothesized to relate to adult-level testosterone and, more recently, to the testosterone response to a challenging situation. In the present work, we tested these core assumptions. Drawing from, in total, 54 studies and 8077 participants, we investigated whether the 2D:4D is related to adult level testosterone (44 studies), testosterone change (6 studies), and prenatal testosterone (10 studies). We found no evidence of the relationship between the above testosterone types and digit ratios. Furthermore, there was no relationship between testosterone and the right and left 2D:4D, male and female 2D:4D, and the 2D:4D and testosterone measurement (i.e., measured in blood or saliva). However, we found some evidence that prenatal testosterone measured in amniotic fluid (but not cord blood) might be related to the digit ratios-further studies are necessary to validate this observation. In summary, considering the current state of knowledge, any conclusions drawn from the assumption of the digit ratios as the proxy for testosterone (prenatal, adult level, or testosterone change under a challenging situation) warrant great caution.

Unveiling Gender Dysphoria Experiences in Turkish Young Adults: Challenges, Perspectives, and Implications in Health Care Settings

Purpose

Gender dysphoria (GD) emerged as a focal area in child and adolescent development research. While the intricacies of diagnosis and interventions for GD intertwine with diverse socio-cultural challenges, a notable dearth of knowledge exists about the experiences of transgender (TG) individuals during their formative years in Turkey. This study aims to unveil these experiences, shedding light on the challenges, perspectives, and implications in health care settings.

Patients and Methods

Our study encompassed 125 participants: 62 TGs under clinical follow-up, and a control group of 63 cisgender individuals. Surveys tailored to TG participants addressed early GD experiences, gender-typed activity participation, and psychosocial challenges from childhood through adolescence. Additionally, both cohorts contributed to a survey on attitudes towards community-based interventions, allowing for a comparative analysis of their perspectives.

Results

TGs identified their GD around age 10.77. Female-to-male TGs showed more involvement in traditionally male-associated activities, whereas male-to-female engaged more in female-associated domestic role-plays (p<0.001). Over a third (37.09%) faced ostracization or bullying due to GD, 45.16% encountered verbal abuse, and 12.90% reported physical violence. Additionally, 40.32% had undergone treatment for depression and anxiety disorders. Most participants supported awareness initiatives, advocating for open gender expression, and normalizing the experiences of TG youth. Furthermore, 88.71% of TGs emphasized the importance of enhancing the expertise of professional groups, such as medical and mental health practitioners, in GD matters, a sentiment echoed by 68.25% of cisgender participants (p=0.030). While medical interventions were the least favored strategy at 32.80% overall, 46.78% of TGs supported it, compared to 19.05% of controls (p=0.010).

Conclusion

Our study underscores the challenges faced by TG individuals during development. Early recognition, societal awareness, enhanced training in professional healthcare environments, and comprehensive support are crucial for fostering acceptance and reducing adversity among children and adolescents navigating GD.

In support of 2D:4D: More data exploring its conflicting results on handedness, sexual orientation and sex differences

In the last few years, several studies have questioned the value of the second-to-fourth digit ratio (2D:4D) as a measure of exposure to sex hormones before birth. Controversy has also extended to the 2D:4D association with individual features previously related to this exposure such as handedness and sexual orientation. Given that it has been argued that sex differences in 2D:4D could be a consequence of body-size differences, we have tested in a large sample the allometric relationship between finger lengths and body size. Our results show that the association is either allometric or isometric, depending on the analyses performed. In any case, the deviation from isometry is not large enough to explain the typically observed sex difference in this trait. We have also tested the association between sexual orientation and 2D:4D, finding a relationship between 2D:4D and sexual orientation in men but not in women. We attribute this discordance with previously published meta-analysis to differences in genetic background, a variable that has gained relevance in recent years in studies involving 2D:4D. Finally, we did not find any relationship between 2D:4D and handedness, evaluated through self-reported preference and hand performance. Our main conclusion is that 2D:4D shows differences between sexes beyond their disparity in body size. In our opinion, 2D:4D can be used cautiously as an indicator of intrauterine exposure to sex hormones taking into account some considerations, such as analysing a very large sample and taking careful measurements of the ethnicity of the sample.

2D:4D biomarker reliability and validity in a within-subject pregnancy-childhood-adolescence cohort

BACKGROUND

A lot of studies use the second-to-fourth digit length ratio (2D:4D) as a biomarker for intrauterine androgen load to predict behavioral and mental health problems. Thus, knowledge of 2D:4D's metric properties, namely reliability and validity, is essential.

METHOD

2D:4D handscans were available from 149 adolescents (M = 13.32 years, SD = 0.35) and their mothers. For 88 adolescents, there were also primary-school age handscans (M = 7.87 years, SD = 0.68). Prenatal risks for the 1st to 3rd trimesters were recorded during the 3rd trimester of pregnancy (alcohol exposition: meconium biomarker and maternal self-report; nicotine exposition: maternal self-report; maternal depressive symptoms and subjective stress: questionnaires).

RESULTS

The 2D:4D ratio was highly stable from childhood to early adolescence. However, both developmental and sex effects were present: The 2D:4D ratio increased with age and was higher in adolescent girls vs. boys. Significant 2D:4D mother-child associations were found for girls. Significant main effects could be found for the prenatal risk factors alcohol (self-report) and nicotine consumption.

CONCLUSION

In line with earlier studies, the 2D:4D biomarker proved to be an inter-individually stable measure with an intra-individual increase from childhood to early adolescence. Sex differences in adolescence and associations with maternal prenatal health behaviour underline the validity of the biomarker. Findings on heritability emphasize the importance of interpreting 2D:4D results in a sex-specific manner.

Androgens and child behavior: Color and toy preferences in children with congenital adrenal hyperplasia (CAH)

Human males and females show average gender/sex differences for certain psychological phenomena. Multiple factors may contribute to these differences, including sex chromosomes, exposure to gonadal hormones, and socialization or learning. This study investigated potential hormonal and socialization/learning influences on gender/sex differences in childhood preferences for color, specifically pink and red vs. blues, and for toys. Children (aged 4 to 11 years) with congenital adrenal hyperplasia (CAH, n = 43 girls and 37 boys), marked by elevated prenatal adrenal androgen exposure, and without CAH (n = 41 girls and 31 boys) were studied. Prior research indicates girls with CAH are masculinized for certain behaviors, such as toy choices, while boys with CAH generally do not differ from boys without CAH. In the current study, children indicated preferences for stereotyped hues of pink vs. blue as well as two control color pairs. They also indicated their preference between gender/sex-typed toys (doll vs. car) presented in black and white, in gender/sex-congruent colors (pink doll vs. blue car) and in gender/sex-incongruent colors (pink car vs. blue doll). Color findings: Control girls preferred stereotyped pink over blue more than boys or girls with CAH did; the latter two groups did not differ in their color preferences. No preference differences occurred for other color pairs. Toy findings: In black/white or gender/sex-congruent colors, boys preferred the car more than control girls or girls with CAH did, while girls with CAH preferred the car more than control girls did. In gender/sex-incongruent colors (pink car vs. blue doll), boys still preferred the car, while girls with CAH showed reduced and control girls showed increased preferences for the pink car compared to the car preferences in black/white. Results support learning theories of color preferences, perhaps also influenced by pre-existing toy preferences which may occur for other reasons, including early androgen exposure. Specifically, girls with CAH may have learned they do not enjoy stereotypical toys for girls, often colored pink, and pink coloring may subsequently diminish their preference for a car. Our results highlight the importance of gonadal hormones and learning in the development of childhood toy and color preferences.

The effects of sex, nation, ethnicity, age and self-reported pubertal development on participant-measured right-left 2D:4D (Dr-l) in the BBC internet study

Digit ratio (2D:4D) - a proxy for prenatal sex steroids - shows sex, nationality and ethnic differences and is linked to pubertal onset. It is unclear whether right-left 2D:4D (Dr-l) also correlates with prenatal sex steroids, as evidence of these differences has been less conclusive. The present study examined the effects of sex, nation, ethnicity, age and self-reported pubertal development (i.e. the rate of physical development and age at menarche [females] or first shave [males]) on Dr-l in a large online study (the BBC internet study). Digit lengths were self-measured in 201,865 adults (110,955 males) and the sample of nations included 41 countries. Participants reported the self-perceived rate of physical pubertal development on a five-point scale (from very slow to very fast) and provided information on the age at menarche or first shave. Adult (>17 years) males had lower Dr-l than females with weak effect size across 41 nations (males-females; d = -.065, p < .0001). There were sex and ethnicity effects on Dr-l across seven ethnic groups with males < females and lower Dr-l in Whites and Middle/Near Eastern participants compared to Asian, Black and Chinese respondents. Considering age effects, the authors focused on participants >12 years; there were stable sex differences and a weak positive effect of age on Dr-l. Dr-l showed a positive relationship with the rate of physical development and a negative relationship with age at menarche or first shave. Relationships were present in males and females with stronger effects in the latter. It is concluded that Dr-l shows a weak sex difference (males < females) independent of nation, ethnicity and age, and suggest that Dr-l is a proxy for prenatal sex steroids.

Gestational Exposure to Phthalates and Phthalate Replacements in Relation to Neurodevelopmental Delays in Early Childhood

Phthalates have been linked to changes in child neurodevelopment. However, sex-specificity has been reported inconsistently, and little is known about the impact of recent phthalate replacement chemicals. Our analysis included mother−child pairs (N = 274) from the PROTECT birth cohort in Puerto Rico. Phthalate metabolites were measured in multiple maternal urine collected during pregnancy. Neurodevelopment was measured at 6, 12, and 24 months of age using the Battelle Developmental Inventory-2nd edition (BDI), which provides scores for adaptive, personal-social, communication, motor, and cognitive domains. Multivariable linear regression was used to examine associations between phthalate metabolite concentrations and BDI scores, adjusting for maternal age, maternal education, child age, and specific gravity. Sex-specificity was assessed with sex X exposure interaction terms and stratified models. Results show that all five domains were significantly associated with mono-3-carboxypropyl phthalate (MCPP) at age 24 months, suggesting a holistic developmental delay related to this metabolite. Sex-specificity existed for all timepoints (p-interaction < 0.2), in general, showing stronger associations among boys. For example, metabolites of a recent phthalate replacement, di-2-ethylhexyl terephthalate (DEHTP), were differentially associated with the adaptive domain (boys −7.53%/IQR, 95% CI: −14.58, −0.48 vs. girls −0.85%/IQR, 95% CI: −5.08, 3.37), and the cognitive domain (boys −6.05%/IQR, 95% CI: −10.88, −1.22 vs. girls −1.93%/IQR, 95%CI: −4.14, 0.28) at 6 months. To conclude, gestational exposure to phthalates and phthalate replacements was associated with neurodevelopmental delay across multiple domains, with differences by sex and child age.

The association of prenatal amniotic sex hormones and digit ratio (2D:4D) in children aged 5 to 70 months: A longitudinal study

The sex difference of the 2D:4D digit ratio (female > male)-a proposed marker for prenatal testosterone exposure-is well established. Studies suggest it already exists in utero and is of moderate effect size in adulthood. However, evidence for the claim that 2D:4D reflects prenatal androgen action is limited, and the sex difference may exhibit lability during childhood. In the present study, 244 mothers were recruited in the course of an amniocentesis examination (performed between gestational weeks 14 and 18). Prenatal testosterone (T) and estradiol (E) levels were determined from amniotic fluid for boys and girls. The majority (97.4%, n = 114) of available female T levels (n = 117) were found below the level of quantification. Therefore, only male amniotic fluid data (n = 117) could be included for the analysis of associations between amniotic sex hormones (T levels and T to E ratio (T/E)) and 2D:4D. The families were then invited to each of the five consecutive follow-ups (ages: 5, 9, 20, 40, and 70 months) where children's 2D:4D was measured for both hands. The alternative marker D[r-l] reflects the directional asymmetry of 2D:4D (right subtracted by left 2D:4D) and was subsequently calculated as an additional measure for prenatal T exposure. No significant correlations between amniotic T or the T/E ratio (measured between week 14 and 18 of gestation) with 2D:4D respectively D[r-l] were observed for any time point. There was a significant sex difference (females > males) and a significant age effect with moderate correlations of 2D:4D between time points. 2D:4D increased between 20 and 40 months and between 40 and 70 months of age. The findings raise questions regarding the applicability of 2D:4D as a marker for prenatal androgen action and are discussed in terms of the reliability of obtained digit ratio data as well as in terms of the developmental timing of amniocentesis.

Fingerprints as Predictors of Schizophrenia: A Deep Learning Study

BACKGROUND AND HYPOTHESIS

The existing developmental bond between fingerprint generation and growth of the central nervous system points to a potential use of fingerprints as risk markers in schizophrenia. However, the high complexity of fingerprints geometrical patterns may require flexible algorithms capable of characterizing such complexity.

STUDY DESIGN

Based on an initial sample of scanned fingerprints from 612 patients with a diagnosis of non-affective psychosis and 844 healthy subjects, we have built deep learning classification algorithms based on convolutional neural networks. Previously, the general architecture of the network was chosen from exploratory fittings carried out with an independent fingerprint dataset from the National Institute of Standards and Technology. The network architecture was then applied for building classification algorithms (patients vs controls) based on single fingers and multi-input models. Unbiased estimates of classification accuracy were obtained by applying a 5-fold cross-validation scheme.

STUDY RESULTS

The highest level of accuracy from networks based on single fingers was achieved by the right thumb network (weighted validation accuracy = 68%), while the highest accuracy from the multi-input models was attained by the model that simultaneously used images from the left thumb, index and middle fingers (weighted validation accuracy = 70%).

CONCLUSION

Although fitted models were based on data from patients with a well established diagnosis, since fingerprints remain lifelong stable after birth, our results imply that fingerprints may be applied as early predictors of psychosis. Specially, if they are used in high prevalence subpopulations such as those of individuals at high risk for psychosis.

L’identité de genre, entre faits naturels et faits construits, une approche intégrative et développementale

À partir des années 1950, l’identité de genre, en ce qu’elle définit la conviction de l’individu d’appartenir à un genre ou à un autre, devient un objet de recherche médicale et scientifique. Partant des premiers travaux de John Money et de Robert Stoller, qui posent la possibilité d’une dimension polyfactorielle de la construction de l’identité de genre, les recherches les plus récentes portant sur les facteurs génétiques, neuroanatomiques, socio-cognitifs et psychodynamiques, réactualisent l’intérêt de pouvoir envisager un modèle polyfactoriel. Le paradigme clinique des variations du développement génital et des troubles du spectre de l’autisme entrouvre des hypothèses quant à l’articulation possible de ces facteurs de différentes natures. Pour appuyer tant ces éléments historiques que les données issues de la recherche actuelle, nous développerons en quoi les pratiques médicales actuelles vis-à-vis du genre s’inscrivent, sur le plan déontologique, dans une approche nécessairement individualisée soutenant un modèle polyfactoriel développemental.

The digit ratio (2D:4D) and testosterone co-predict vertical jump performance in athletic boys: Evidence of organizational and activational effects of testosterone on physical fitness

The digit ratio (2D:4D) is a negative correlate of boy's physical fitness, and thought to arise from organizational effects of prenatal testosterone on different bodily systems. During human ontogeny, activational effects of testosterone on body size and strength offers another pathway to physical fitness. We tested these hypotheses by examining the organizational and activational effects of testosterone on vertical jump performance in athletic boys. Using a cross-sectional design, 173 boys (aged 9 to 18 years) were tested for standing height, body mass, body fat, fat-free mass, weekly training activity, training history, salivary testosterone and cortisol, R2D:4D, L2D:4D, and right-left 2D:4D (Dr-1), and vertical height in 3 different countermovement jump (CMJ) tests. A generalized additive model was employed to delineate age-related trajectories and predict CMJ performance. Our models yielded significant non-linear increases (or changes) in body size, current hormone concentration, training outcomes, and CMJ performance with chronological age. All 2D:4D measures were age invariant. The R2D:4D and testosterone were significant non-linear predictors of CMJ height with (R² = 66.2%) or without (R² = 54.3%) covariates, whereby a higher current testosterone concentration (up to a certain level) and a lower or higher R2D:4D were linked to better performance. The L2D:4D and Dr-1 had no predictive value. In conclusion, the R2D:4D and testosterone were co-predictors of CMJ height among athletic boys, with non-linear performance effects that differed in timing, tempo, and direction. Our findings confirm that testosterone can regulate a simple measure of boy's physical fitness through both an activational and organizational pathway.

Cognitive Performances: The Role of Digit Ratio (D2:D4) With a Protective Factor for Anxiety

This study aimed to identify a possible correlation between the D2:D4 ratio and state and/or trait anxiety in adult healthy subjects and, if so, whether it exists any difference between men and women. In addition, we also wanted to observe whether there is a relationship between participants' age and state and/or trait anxiety. The research involved 125 subjects of both sexes, who were calculated the D2:D4 ratio and were administered the self-assessment questionnaire State-Trait Anxiety Inventory (STAI-Y). Results show that there are positive significant correlations between the D2:D4 ratio and score at state anxiety and trait anxiety, in the total sample. However, if men are examined separately from women, it can be observed that only men have a statistically significant relationship between D2:D4 ratios and state anxiety and trait anxiety. Moreover, about possible relations between the age of participants and state and trait anxiety, a significant negative relationship was observed, without differences between men and women. However, only subjects with a D2:D4 ratio ≥ 1, without differences between men and women, showed a statistically significant negative linear correlation between their age and their state and trait anxiety. The present data allow us to conclude that a low D2:D4 ratio (<1) represents a protective factor against anxiety in both men and women and that this protection seems likely to act throughout life.

The fMRI correlates of visuo-spatial abilities: sex differences and gender dysphoria

The contribution of brain regions to visuospatial abilities according to sex differences and gender identity is inconsistently described. One potential explaining factor may be the different tasks employed requiring a variable load of working memory and other cognitive resources. Here we asked to 20 cis and 20 transgender participants to undergo functional Magnetic Resonance Imaging during performance of a judgement line of orientation test that was adapted to explore the basic visuospatial processing while minimizing the working memory load. We show that V1 activation may be viewed as a brain area with enhanced activation in males, regardless of participants’ gender identity. On its turn, gender identity exclusively influences the visuospatial processing of extrastriate visual areas (V5) in women with gender dysphoria. They showed enhanced V5 activation and an increased functional connectivity between V5 and V1. Overall our neuroimaging results suggest that the basic visuospatial abilities are associated with different activations pattern of cortical visual areas depending on the sex assigned at birth and gender identity.

Prenatal testosterone and sexually differentiated childhood play preferences: a meta-analysis of amniotic fluid studies

Sexually differentiated behaviour appears to emerge from a complex interaction of biological and socio-cultural factors, with prenatal exposure to steroid hormones such as testosterone thought to play a key role. Due to large sex differences being present from a very early age, much research has focussed on the influence these hormones may have on play preferences during childhood. We present an overview of the literature and a random-effects meta-analysis linking amniotic testosterone with sexually differentiated play preferences (k = 9, n = 493). The overall effect size estimate was in the theory-consistent direction (i.e., with higher levels of testosterone associated with more male-typical play preferences), though not statistically significant (r = 0.082, p = 0.274). However, after three hypothesised missing studies were imputed via the trim and fill procedure, a significant correlation emerged (r = 0.166, p = 0.014). Nevertheless, one sample was observed to exert a particularly large influence on the outcome of the analysis. Notably this was the second biggest sample and related to the largest effect size estimate. Though far from conclusive, the overall findings are consistent with the idea that individual differences in prenatal testosterone within the typical range predict sexually differentiated play preferences in early life. However, these effects may be small in magnitude and appear to vary considerably across studies.

Hypertensive disorders during pregnancy and polycystic ovary syndrome are associated with child communication and social skills in a sex-specific and androgen-dependent manner

Prenatal exposure to testosterone is implicated in the etiology of autism spectrum disorder (ASD). Hypertensive disorders of pregnancy and polycystic ovary syndrome are associated with both hyperandrogenism and increased risk for ASD. We examined whether increased maternal testosterone mediates the relationship between these hyperandrogenic disorders (HDs) during pregnancy and child communication and social skills. Maternal plasma was collected during the second trimester and parent-report measures of child communication and social skills were obtained at 4.5-6.5 years of age from 270 participants enrolled in the Nulliparous Pregnancy Outcomes Study: Monitoring Mothers-to-be (nuMoM2b). Our retrospective frequency-matched cohort study design identified 58 mothers with one or both of the HDs and 58 matched controls. Women diagnosed with an HD who carried a female had higher testosterone levels compared to those carrying a male (t(56) = -2.70, p = 0.01). Compared to females controls, females born to women with an HD had significantly higher scores on the Social Communication Questionnaire (t(114) = -2.82, p =0.01). Maternal testosterone partially mediated the relationship between a diagnosis of an HD and SCQ scores among females. These findings point to sex-specific associations of two HDs - hypertensive disorders of pregnancy and polycystic ovary syndrome - on child communication and social skills and a mediating effect of maternal testosterone during pregnancy. Further research is needed to understand placental-mediated effects of maternal testosterone on child brain development and neurodevelopmental outcomes.

Exploring the sex and gender correlates of cognitive sex differences

The correlates of cognitive sex differences are yet to be fully understood. Many biological and psychosocial factors modulate these cognitive abilities leading to mixed results in the scientific literature. The current study aims to explore the different parameters potentially influencing cognitive abilities acting in synergy. Sex and gender correlates of cognitive functioning were assessed in a sample of individuals ages 18 to 45 years (N = 87) from diverse sexual orientations. Sex hormones were assessed via saliva samples at four timepoints throughout the testing. Gender roles, sexual orientation and socio-demographics were measured via self-report questionnaires. Participants completed mental rotation and verbal fluency tasks. Men performed better than women at mental rotation, while no significant difference was found for verbal fluency. Significant positive associations were observed between estradiol and word fluency for the naturally cycling women compared to the women using oral contraception. While controlling for sex hormones, a significant interaction effect of sex by gender roles was identified for mental rotation among masculine women. These exploratory results suggest an effect principally driven by sex and sex hormones on cognitive performance that will need to be furthered with larger studies.

Investigating the reliability and sex differences of digit lengths, ratios, and hand measures in infants

Hands and digits tend to be sexually dimorphic and may reflect prenatal androgen exposure. In the past years, the literature introduced several hand and digit measures, but there is a lack of studies in prepubertal cohorts. The available literature reports more heterogeneous findings in prepubertal compared to postpubertal cohorts. The comparability of the available studies is further limited by the study design and different measurement techniques. The present study compared the reliability and sex differences of available hand and digit measures, namely digit lengths of 2D, 3D, 4D, 5D, digit ratios 2D:4D, 2D:5D, 3D:4D, 3D:5D, 4D:5D, relative digit lengths rel2, rel3, rel4, rel5, directional asymmetry of right and left 2D:4D (D_r-l), hand width, length, and index of 399 male and 364 female 6-month-old German infants within one study using only indirect and computer-assisted measurements. The inter-examiner reliability was excellent while the test-retest reliability of hand scans was only moderate to high. Boys exhibited longer digits as well as wider and longer hands than girls, but smaller digit ratios, with ratios comprising the fifth digit revealing the largest effect sizes. Other hand and digit ratios revealed sex differences to some extent. The findings promote the assumption of sexual dimorphic hand and digit measures. However, by comparing the results of the available literature, there remains an uncertainty regarding the underlying hypothesis. Specifically in prepubertal cohorts, i.e. before the influence of fluctuating hormones, significant effects should be expected. It seems like other factors than the influence of prenatal androgens contribute to the sexual dimorphism in hand and digit lengths.

Cord blood androgen levels of females from same sex and opposite sex twins - A pilot study

OBJECTIVE

Opposite-sex twins have shown behavioural and reproductive differences between females and males. These differences may be determined by higher intrauterine levels of androgens among females that were exposed to a male co-twin. The aim of this study was to compare cord blood androgen levels in females from same-sex and opposite-sex twins.

DESIGN

A prospective study. In this pilot study, we compared cord blood androgens (DHEA-S, Δ-4 androstenedione, total testosterone-TT) and sex hormone-binding globulin (SHBG) levels in 20 females from same sex and 20 females from opposite-sex dichorionic diamniotic twins. We used generalized estimating equation (GEE) modelling to assess differences in cord blood androgens between females from same-sex twin pregnancies and females from opposite-sex twin pregnancies.

PATIENTS

Twenty opposite-sex twin pairs (female-male twins) and 20 same-sex twin pairs (female-female).

MEASUREMENTS

Cord blood total testosterone, Δ-4 androstenedione, DHEA-S and sex hormone-binding globulin (SHBG) levels.

RESULTS

No difference in the levels of androgens as Δ-4 androstenedione, total testosterone and SHBG was identified between females that were exposed to a female co-twin compared with females that were exposed to a male co-twin. DHEA-S levels were significantly lower among females from opposite-sex twins compared with females from same-sex twins.

CONCLUSIONS

Our preliminary data do not support the hypothesis that females exposed to male co-twins are exposed to higher levels of androgens in utero compared with females exposed to female co-twins. Further studies are needed to explain the reported behavioural and reproductive differences among opposite-sex twins.

Markers of Prenatal Androgen Exposure Correlate With Online Sexual Compulsivity and Erectile Function in Young Men

Pornography addiction and sexual dysfunction are increasingly prevalent in young men. Previous studies suggest that prenatal androgen exposure plays a role in addiction and sexual functionality. Here, we tested whether lower second-to-fourth finger length ratio (2D:4D) and later age at spermarche, both putative indicators of higher androgen levels in utero, correlate with online sexual compulsivity (OSC scale of ISST), erectile function (IIEF-5), and ejaculatory control (PEPA) in 4,370 young men (age IQR: 25-26 years) of the Cohort Study on Substance Use Risk Factors. Statistical analyses revealed that lower 2D:4D correlated with higher scores on the OSC scale. Moreover, higher age at spermarche correlated with higher OSC scores and decreased erectile function. Interestingly, OSC severity, but not the frequency of pornography use, correlated negatively with erectile function and ejaculatory control. This is the first study to associate two independent proxies of prenatal testosterone level with OSC. These findings provide novel insight into intrauterine predisposition of sexual behavior and related sexual function in adulthood.

Prenatal androgen exposure and children's gender-typed behavior and toy and playmate preferences

We report findings from two studies investigating possible relations of prenatal androgen exposure to a broad measure of children's gender-typed behavior, as well as specifically to children's toy and playmate preferences. Study 1 investigated these outcomes for 43 girls and 38 boys, aged 4 to 11 years, with congenital adrenal hyperplasia (CAH, a genetic condition causing increased adrenal androgen production beginning prenatally) compared to similarly-aged, unaffected relatives (41 girls, 31 boys). The predicted sex differences were found for all of the outcome measures. Furthermore, girls with CAH showed increased male-typical and decreased female-typical behavior and toy and playmate preferences compared to unaffected girls. Study 2 investigated the relationship of amniotic fluid testosterone to gender-typed behavior and toy and playmate preferences in typically developing children (48 girls, 44 boys) aged 3 to 5 years. Although the predicted sex differences were found for all of the outcome measures, amniotic fluid testosterone was not a significant correlate, in the predicted direction, of any outcome measure for either sex. The results of study 1 provide additional support for an influence of prenatal androgen exposure on children's gender-typed behavior, including toy and playmate preferences. The results of study 2 do not, but amniotic fluid testosterone may be an insufficiently sensitive measure of early androgen exposure. A more sensitive and reliable measure of prenatal androgen exposure may be needed to consistently detect relations to later gender typed behavior in non-clinical populations.

Gender Identity and Assignment Recommendations in Disorders of Sex Development Patients: 20 Years’ Experience and Challenges

OBJECTIVE

Gender assignment in infants and children with disorders of sex development (DSD) is a stressful situation for both patient/families and medical professionals.

METHODS

The purpose of this study was to investigate the results of gender assignment recommendations in children with DSD in our clinic from 1999 through 2019.

RESULTS

The mean age of the 226 patients with DSD at the time of first admission were 3.05±4.70 years. 50.9% of patients were 46,XY DSD, 42.9% were 46,XX DSD and 6.2% were sex chromosome DSD. Congenital adrenal hyperplasia (majority of patients had 21-hydroxylase deficiency) was the most common etiological cause of 46,XX DSD. In 46,XX patients, 87 of 99 (89.7%) were recommended to be supported as a female, 6 as a male, and 4 were followed up. In 46,XY patients, 40 of 115 (34.8%) were recommended to be supported as a female, and 70 as male (60.9%), and 5 were followed up. In sex chromosome DSD patients, 3 of 14 were recommended to be supported as a female, 9 as a male. The greatest difficulty in making gender assignment recommendations were in the 46,XY DSD group.

CONCLUSION

In DSD gender assignment recommendations, the etiologic diagnosis, psychiatric gender orientation, expectation of the family, phallus length and Prader stage were effective in the gender assignment in DSD cases, especially the first two criteria. It is important to share these experiences among the medical professionals who are routinely charged with this difficult task in multidisciplinary councils.

Assessment of Facial Morphologic Features in Patients With Congenital Adrenal Hyperplasia Using Deep Learning

IMPORTANCE

Congenital adrenal hyperplasia (CAH) is the most common primary adrenal insufficiency in children, involving excess androgens secondary to disrupted steroidogenesis as early as the seventh gestational week of life. Although structural brain abnormalities are seen in CAH, little is known about facial morphology.

OBJECTIVE

To investigate differences in facial morphologic features between patients with CAH and control individuals with use of machine learning.

DESIGN, SETTING, AND PARTICIPANTS

This cross-sectional study was performed at a pediatric tertiary center in Southern California, from November 2017 to December 2019. Patients younger than 30 years with a biochemical diagnosis of classical CAH due to 21-hydroxylase deficiency and otherwise healthy controls were recruited from the clinic, and face images were acquired. Additional controls were selected from public face image data sets.

MAIN OUTCOMES AND MEASURES

The main outcome was prediction of CAH, as performed by machine learning (linear discriminant analysis, random forests, deep neural networks). Handcrafted features and learned representations were studied for CAH score prediction, and deformation analysis of facial landmarks and regionwise analyses were performed. A 6-fold cross-validation strategy was used to avoid overfitting and bias.

RESULTS

The study included 102 patients with CAH (62 [60.8%] female; mean [SD] age, 11.6 [7.1] years) and 59 controls (30 [50.8%] female; mean [SD] age, 9.0 [5.2] years) from the clinic and 85 controls (48 [60%] female; age, <29 years) from face databases. With use of deep neural networks, a mean (SD) AUC of 92% (3%) was found for accurately predicting CAH over 6 folds. With use of classical machine learning and handcrafted facial features, mean (SD) AUCs of 86% (5%) in linear discriminant analysis and 83% (3%) in random forests were obtained for predicting CAH over 6 folds. There was a deviation of facial features between groups using deformation fields generated from facial landmark templates. Regionwise analysis and class activation maps (deep learning of regions) revealed that the nose and upper face were most contributory (mean [SD] AUC: 69% [17%] and 71% [13%], respectively).

CONCLUSIONS AND RELEVANCE

The findings suggest that facial morphologic features in patients with CAH is distinct and that deep learning can discover subtle facial features to predict CAH. Longitudinal study of facial morphology as a phenotypic biomarker may help expand understanding of adverse lifespan outcomes for patients with CAH.

Gestational and childhood exposure to phthalates and child behavior

BACKGROUND

Early-life phthalate exposures may adversely influence neurodevelopment by disrupting thyroid hormone homeostasis, altering brain lipid metabolism, or reducing gonadal hormone concentrations. Previous literature examining gestational phthalate exposure and child behavior were inconclusive and few prospective studies have examined childhood phthalate exposure, particularly phthalate mixtures. We investigated whether gestational and childhood phthalate exposures were associated with child behavior.

METHODS

We used data from 314 mother-child pairs in the HOME Study, a longitudinal pregnancy and birth cohort that enrolled pregnant women from Cincinnati, Ohio. We quantified urinary concentrations of 11 phthalate metabolites in samples collected twice during gestation from women and six times from their children when they were ages 1, 2, 3, 4, 5, and 8 years. We assessed children's behavior at ages 2, 3, 4, 5, and 8 years using the Behavioral Assessment System for Children-2. Using linear mixed models, we estimated covariate-adjusted associations of measurement-error-corrected gestational and childhood phthalate metabolite concentrations (per interquartile range increase) with repeated child behavior assessments. We used Weighted Quantile Sum (WQS) regression to estimate the association of phthalate mixtures with child behavior.

RESULTS

Gestational mono(3-carboxypropyl) phthalate (MCPP) concentrations were associated with more problem behaviors (internalizing: β = 0.9, 95% confidence interval [CI] = -0.1, 1.9; externalizing: β = 1.0, 95%CI = -0.1, 2.0; behavioral symptoms index [BSI]: β = 1.1, 95%CI = 0.1, 2.1). Higher childhood monobenzyl phthalate (MBzP) (β = 1.4; 95%CI = 0.0, 2.7), monocarboxynonyl phthalate (MCNP) (β = 3.2; 95%CI = 1.6, 4.8), monocarboxyoctyl phthalate (MCOP) (β = 0.9; 95%CI = 0.0, 1.7), MCPP (β = 1.8; 95%CI = 0.2, 3.5), and monoethyl phthalate (MEP) (β = 1.6; 95%CI = 0.1, 3.1) concentrations were associated with higher BSI composite scores. Consistent with this, the weighted childhood phthalate index was associated with more problem behaviors (internalizing: β = 1.5, 95%CI = -0.2, 3.1; externalizing: β = 1.7, 95%CI = 0.1, 3.5; BSI: β = 1.7, 95%CI = 0.2, 3.2); MBzP, MCNP, and MEP largely contributed to these associations.

CONCLUSION

Our findings suggest that childhood exposure to phthalate mixtures may be associated with children's problem behaviors.

Digit ratio (2D:4D) and congenital adrenal hyperplasia (CAH): Systematic literature review and meta-analysis

The ratio of length between the second and fourth fingers (2D:4D) is commonly used as an indicator of prenatal sex hormone exposure. Several approaches have been used to try to validate the measure, including examining 2D:4D in people with congenital adrenal hyperplasia (CAH), a suite of conditions characterised by elevated adrenal androgen production secondary to defective steroidogenesis. We present a systematic review and meta-analysis that examines the relationship between these two variables. Twelve articles relating to nine CAH cohorts were identified, and 2D:4D comparisons have been made between cases and controls in eight of these cohorts. Altogether, at least one 2D:4D variable has been compared between n = 251 females with CAH and n = 358 unaffected females, and between n = 108 males with CAH and n = 204 unaffected males. A previous meta-analysis (Hönekopp and Watson, 2010) reported lower right hand (R2D:4D) and left hand (L2D:4D) digit ratios in patients with CAH relative to sex-matched controls. Our meta-analysis showed the same pattern, with medium effect sizes for R2D:4D and small effect sizes for L2D:4D. Differences of small magnitude were also observed for M2D:4D, and no significant effects were observed for D_[R-L]. Notably, the only effects that remained statistically significant when stratified by sex were R2D:4D in males and L2D:4D in females, and the average effect size had reduced by 46.70% since the meta-analysis of Hönekopp and Watson (2010). We also found that individual comparisons in this literature were considerably underpowered, and that patterns of sexual dimorphism in 2D:4D were similar in CAH samples as in typically developing populations. Findings are discussed in relation to the prenatal androgen hypothesis as well as alternative explanations.

Sexual Dimorphism in Titi Monkeys' Digit (2D:4D) Ratio is Associated with Maternal Urinary Sex Hormones During Pregnancy

The second-to-fourth digit (2D:4D) ratio is a sexually-dimorphic biomarker for prenatal sex hormone exposure. We investigated whether titi monkeys (Plecturocebus cupreus) exhibit sexually-dimorphic 2D:4D ratio, and whether variation in 2D:4D ratio correlates with maternal testosterone and estrogen levels during early pregnancy. Subjects were 61 adult titi monkeys (32 males, 29 females). For 26 subjects, maternal urine samples were collected approximately 15-20 weeks before birth and assayed for testosterone and estrone conjugate (E1 C). Titi monkeys exhibited a human-like pattern of sexual dimorphism in right-hand 2D:4D ratio, with females exhibiting higher 2D:4D ratio than males (β = -0.29, p = 0.023). For left-hand 2D:4D ratio, high levels of maternal E1 C predicted low offspring 2D:4D ratio (β = -0.48, p = 0.009). For right-hand 2D:4D ratio, high levels of testosterone (β = -0.53, p = 0.005) and testosterone-to-E1 C ratio (β = -0.41, p = 0.028) predicted low offspring 2D:4D ratio. For 2D:4D ratio asymmetry (right-hand - left-hand), high levels of testosterone (β = -0.43, p = 0.03) and testosterone-to-E1 C ratio (β = -0.53, p = 0.003) predicted low (right-biased) asymmetry. This is the first report of sexually-dimorphic 2D:4D ratio in New World monkeys, and the results support a growing literature suggesting prenatal sex hormones may modulate offspring 2D:4D ratio.

Parent-Reports of Sex-Typed Play Preference in Preschool Children: Relationships to 2D:4D Digit Ratio and Older Siblings' Sex

Sex-typed play behavior shows large sex differences and seems to be affected by prenatal sex hormones. For example, a smaller, more male-typical ratio between the second and fourth digit length (2D:4D), a proposed marker for prenatal testosterone exposure, has been shown to be related to sex-typed play preference in childhood. Nevertheless, it is still being debated whether 2D:4D displays a stable sex difference throughout childhood, as there are few longitudinal studies. In the present study, children's 2D:4D was measured on both hands on four occasions from early infancy to early childhood (T1: 5 months, T2: 9 months, T3: 20 months, and T4: 40 months) providing the rare possibility to test the temporal stability of the sex difference. Parents completed the Preschool Activities Inventory at T4 and reported on the number of older brothers and sisters as a measure for socialization influences. Parents described boys as playing more masculine and less feminine than girls. Boys had smaller 2D:4D than girls at all measurements (T1-T4) and on both hands (right/left). Nevertheless, 2D:4D increased significantly from T3 to T4 in both sexes. Girls, but not boys, who were described as playing more masculine and less feminine had more masculine 2D:4D ratios at T1-T4 on both hands (except for right 2D:4D at T2 and T3) and had more older brothers and fewer older sisters. These data underline the stability of the sex difference in 2D:4D and show the importance of both biological and social influences on sex-typed play behavior.

Identity, Sexuality, and Parenthood in Women with Congenital Adrenal Hyperplasia

STUDY OBJECTIVE

To explore how women with congenital adrenal hyperplasia (CAH) describe their experiences of gender role behavior, psychosexual development, and intimate relationships. CAH results in increased androgen exposure in affected females, and is the most common reason for unclear sex at birth. Women with CAH have been studied to find answers to the role of androgens in psychosexual development. Nevertheless, factors that may account for the variability of outcomes in women with CAH are unclear.

DESIGN, SETTING AND PARTICIPANTS

This was a qualitative study with 13 Swedish women (aged ≥18 years) with CAH. Semi-structured interviews were analyzed using inductive content analysis.

MAIN OUTCOME MEASURES

Direct quotes of patients' experiences derived from interview transcripts were sorted in categories, subcategories, and according to latent theme.

RESULTS

The main categories were "forming identity" and "establishing relationships." Forming identity encompasses that of a girl, a tomboy, and/or a woman. Establishing relationships focuses on intimate relationships, pregnancy, and parenthood. A latent theme was interpreted as "shifting perspectives," with CAH being the main focus of some participants' lives but a side issue for others.

CONCLUSION

These women's experiences are varied and describe shifting perspectives on how much CAH affects their lives. Health care providers can play an important role in helping women with CAH to separate what is caused by the condition and what is not. The long-term goal is to help girls and women to feel in control of their condition across their whole life.

Multi-aspect testing and ranking inference to quantify dimorphism in the cytoarchitecture of cerebellum of male, female and intersex individuals: a model applied to bovine brains

The dimorphism among male, female and freemartin intersex bovines, focusing on the vermal lobules VIII and IX, was analyzed using a novel data analytics approach to quantify morphometric differences in the cytoarchitecture of digitalized sections of the cerebellum. This methodology consists of multivariate and multi-aspect testing for cytoarchitecture-ranking, based on neuronal cell complexity among populations defined by factors, such as sex, age or pathology. In this context, we computed a set of shape descriptors of the neural cell morphology, categorized them into three domains named size, regularity and density, respectively. The output and results of our methodology are multivariate in nature, allowing an in-depth analysis of the cytoarchitectonic organization and morphology of cells. Interestingly, the Purkinje neurons and the underlying granule cells revealed the same morphological pattern: female possessed larger, denser and more irregular neurons than males. In the Freemartin, Purkinje neurons showed an intermediate setting between males and females, while the granule cells were the largest, most regular and dense. This methodology could be a powerful instrument to carry out morphometric analysis providing robust bases for objective tissue screening, especially in the field of neurodegenerative pathologies.

Phthalate and Bisphenol Exposure during Pregnancy and Offspring Nonverbal IQ

BACKGROUND

Prenatal exposures to phthalates and bisphenols are associated with impaired brain development in animals. However, epidemiological studies investigating the association between prenatal phthalate or bisphenol exposure and cognition have produced mixed findings and mostly had modest sample sizes and measured the exposure during the third trimester.

OBJECTIVE

We examined the association between pregnancy maternal urinary biomarkers of phthalate or bisphenol exposure and nonverbal intelligence quotient (IQ) in children 6 years of age.

METHOD

The study sample consisted of 1,282 mother-child pairs participating in the Generation R Study, a population-based birth cohort in Rotterdam, Netherlands (enrollment 2002-2006). We measured maternal urinary concentrations of 18 phthalate metabolites and 8 bisphenols at < 18 , 18-25, and > 25  wks of gestation. Child nonverbal IQ was measured at 6 years of age using the Snijders-Oomen Nonverbal Intelligence Test-Revised. Linear regression models were fit for each of the three collection phases separately, the three collection phases jointly, and for the averaged prenatal exposure across pregnancy.

RESULTS

Higher urinary concentrations of phthalate metabolites during early pregnancy were associated with lower child nonverbal IQ score [e.g., B per 10-fold increase in summed low-molecular weight phthalates = - 1.7 (95% CI: - 3.1 , - 0.3 )]. This association remained unchanged when adjusted for mid and late pregnancy exposures. We also observed an inverse association between late pregnancy di-n-octyl phthalate (DNOP) exposure and nonverbal IQ. Maternal urinary concentrations of bisphenols were not associated with child nonverbal IQ. There was no effect estimate modification by sex.

CONCLUSIONS

We did not observe that maternal biomarkers of bisphenol exposure are associated with nonverbal IQ. We found that phthalate exposure in early pregnancy and DNOP exposure in late pregnancy are associated with lower nonverbal IQ scores in children. Our results might suggest that particularly early pregnancy is a sensitive window of phthalate exposure, but future studies are needed to replicate our findings. https://doi.org/10.1289/EHP6047.

Dementia risk in women higher in same-sex than opposite-sex twins

INTRODUCTION

Hormones may be one possible mechanism underlying sex differences in dementia incidence. We examined whether presumed differential prenatal hormone milieu is related to dementia risk by comparing dementia rates in same- and opposite-sex dizygotic twin pairs in male and female twins.

METHODS

The sample comprised 43,254 individuals from dizygotic twin pairs aged 60 and older from the Swedish Twin Registry. Survival analyses were conducted separately for females and males.

RESULTS

Female twins from opposite-sex pairs had significantly lower dementia risk than female twins from same-sex pairs, but the differences emerged only after age 70 (hazard ratio = 0.64, P = 0.004). Results were not explained by postnatal risk factors for dementia, and no interaction between twin type and apolipoprotein E (APOE) ε4 was found. Male twins from same-sex versus opposite-sex pairs did not differ significantly.

DISCUSSION

The results suggest that relatively masculine prenatal hormone milieus correlate with lower dementia risk in females.

Motion corrected MRI differentiates male and female human brain growth trajectories from mid-gestation

It is of considerable scientific, medical, and societal interest to understand the developmental origins of differences between male and female brains. Here we report the use of advances in MR imaging and analysis to accurately measure global, lobe and millimetre scale growth trajectory patterns over 18 gestational weeks in normal pregnancies with repeated measures. Statistical modelling of absolute growth trajectories revealed underlying differences in many measures, potentially reflecting overall body size differences. However, models of relative growth accounting for global measures revealed a complex temporal form, with strikingly similar cortical development in males and females at lobe scales. In contrast, local cortical growth patterns and larger scale white matter volume and surface measures differed significantly between male and female. Many proportional differences were maintained during neurogenesis and over 18 weeks of growth. These indicate sex related sculpting of neuroanatomy begins early in development, before cortical folding, potentially influencing postnatal development.

Neural Correlates of Gender Face Perception in Transgender People

To date, MRI studies focused on brain sexual dimorphism have not explored the presence of specific neural patterns in gender dysphoria (GD) using gender discrimination tasks. Considering the central role of body image in GD, the present study aims to evaluate brain activation patterns with 3T-scanner functional MRI (fMRI) during gender face discrimination task in a sample of 20 hormone-naïve transgender and 20 cisgender individuals. Additionally, participants were asked to complete psychometric measures. The between-group analysis of average blood oxygenation level dependent (BOLD) activations of female vs. male face contrast showed a significant positive cluster in the bilateral precuneus in transmen when compared to the ciswomen. In addition. the transwomen group compared to the cismen showed higher activations also in the precuneus, as well as in the posterior cingulate gyrus, the angular gyrus and the lateral occipital cortices. Moreover, the activation of precuneus, angular gyrus, lateral occipital cortices and posterior cingulate gyrus was significantly associated with higher levels of body uneasiness. These results show for the first time the existence of a possible specific GD-neural pattern. However, it remains unclear if the differences in brain phenotype of transgender people may be the result of a sex-atypical neural development or of a lifelong experience of gender non-conformity.

The association of sex of co-twin and birth size in twins born in Yucatan, Mexico between 2008 and 2017

Background: Birth measures of twins are potentially influenced by sex of co-twin.Aim: To analyse the association between sex of co-twin and birth weight, length and ponderal index in twin infants from Yucatan, Mexico.Subjects and methods: A total of 2057 twin pairs born during 2008-2017 were analysed. Female-female (F-F), male-male (M-M) and male-female (M-F) twin pair types were defined. Multiple linear regression models were used to analyse the association of (1) being female from M-F pairs and birth measures among overall female infants (M-F and F-F), and (2) being male from M-F pairs and birth measures among overall male infants (M-F and M-M). The length of gestation and mothers' age and level of education were used as covariates.Results: Models showed that being male from M-F pairs was associated with increases of 81 g in birth weight and 0.61 cm in length, compared to males from M-M pairs, and being female from opposite-sex pairs was associated with increases of 0.36 cm in length, compared to females from same-sex pairs.Conclusions: Males from M-F pairs show greater birth size than males from same-sex pairs, which supports the hypothesis that birth measures of twins are influenced by sex of the co-twin.

Prenatal exposure to bisphenol A and its alternatives and child neurodevelopment at 2 years

While increasing evidence has shown that prenatal bisphenol A (BPA) exposure is adversely associated with child neurodevelopment, little is known about the neurodevelopmental effects of BPA alternatives, such as bisphenol S (BPS) and bisphenol F (BPF). We aimed to evaluate the relationships of repeated measurements of bisphenol exposure during pregnancy with child neurodevelopment. From 2014-2015, 456 mother-child pairs were included in the present study. Each had a spot urine sample in the first, second, and third trimester, respectively, during pregnancy for BPA, BPS, and BPF measurements. Children's neurodevelopment was assessed using the Bayley Scales of Infant Development at 2 years. In adjusted models, children's psychomotor development index scores decreased across quartiles of BPS concentrations [-5.52 (95 % CI: -10.06, -0.99) in the 4th quartile vs. 1 st quartile, P-trend = 0.01]. Each 10-fold increase in BPA concentrations was related to lower mental development index scores only in the second trimester [-2.87 (95 % CI: -4.98, -0.75), P_{trimester-int} = 0.04]. However, prenatal BPF exposure was not significantly associated with child neurodevelopment. We provide evidence that prenatal exposure to BPA and BPS may affect child neurodevelopment.

Phthalate exposure and neurodevelopment: A systematic review and meta-analysis of human epidemiological evidence

OBJECTIVE

We performed a systematic review of the epidemiology literature to identify the neurodevelopmental effects associated with phthalate exposure.

DATA SOURCES AND STUDY ELIGIBILITY CRITERIA

Six phthalates were included in the review: di(2-ethylhexyl) phthalate (DEHP), diisononyl phthalate (DINP), dibutyl phthalate (DBP), diisobutyl phthalate (DIBP), butyl benzyl phthalate (BBP), and diethyl phthalate (DEP). The initial literature search (of PubMed, Web of Science, and Toxline) included all studies of neurodevelopmental effects in humans, and outcomes were selected for full systematic review based on data availability.

STUDY EVALUATION AND SYNTHESIS METHODS

Studies of neurodevelopmental effects were evaluated using criteria defined a priori for risk of bias and sensitivity by two reviewers using a domain-based approach. Evidence was synthesized by outcome and phthalate and strength of evidence was summarized using a structured framework. For studies of cognition and motor effects in children ≤4 years old, a random effects meta-analysis was performed.

RESULTS

The primary outcomes reviewed here are (number of studies in parentheses): cognition (14), motor effects (9), behavior, including attention deficit hyperactivity disorder (20), infant behavior (3), and social behavior, including autism spectrum disorder (7). For each phthalate/outcome combination, there was slight or indeterminate evidence of an association, with the exception of motor effects for BBP, which had moderate evidence.

CONCLUSIONS AND IMPLICATIONS OF KEY FINDINGS

Overall, there is not a clear pattern of association between prenatal phthalate exposures and neurodevelopment. There are several possible reasons for the observed null associations related to exposure misclassification, periods of heightened susceptibility, sex-specific effects, and the effects of phthalate mixtures. Until these limitations are adequately addressed in the epidemiology literature, these findings should not be interpreted as evidence that there are no neurodevelopmental effects of phthalate exposure. The views expressed are those of the authors and do not necessarily represent the views or policies of the U.S. EPA.

Brain Sex Differences Related to Gender Identity Development: Genes or Hormones?

The complex process of sexual differentiation is known to be influenced by biological and environmental determinants. The present review has the aim of summarizing the most relevant studies on the biological basis of sexual development, and in particular, it focuses on the impact of sex hormones and genetic background on the development of sexual differentiation and gender identity. The authors conducted a search of published studies on Medline (from January 1948 to December 2019). The evidence suggests that the sexual dimorphic brain could be the anatomical substrate of psychosexual development, on which gonadal hormones may have a shaping role during prenatal and pubertal periods. Additionally, according to several heritability studies, genetic components may have a role, but a promising candidate gene has not been identified. Even though growing evidence underlines the primary role of biological factors on psychosexual development, further studies are necessary to better explain their complex interactions.

Prenatal sex hormones and behavioral outcomes in children

Abnormal sex hormone levels in utero have been associated with child behavioral problems, but it is unclear if normal variation in prenatal sex hormones is associated with subsequent behavior in childhood. We assessed maternal sex hormones, including serum estrone (E1), estradiol (E2), estriol (E3), free testosterone (FT), and total testosterone (TT), during early pregnancy (gestational week 6-21 (mean = 11.1)) and evaluated child behavior at ages 4-5 using the Behavioral Assessment System for Children (BASC-2) and Social Responsiveness Scale (SRS-2) in 404 mother/child pairs (211 girls, 193 boys) within The Infant Development and Environment Study, a multi-site pregnancy cohort study. Associations between hormones and composite scores were evaluated using multiple linear regressions in both sexes combined, and separate models assessed effect modification by sex with the addition of interaction terms. A 10-fold increase in maternal FT or TT was associated in both sexes with a 4.3-point (95 % CI: 0.5, 8.2) or 4.4-point (0.8, 8.0) higher BASC-2 internalizing composite T score, respectively. In addition, a 10-fold increase in FT or TT was associated with a 3.8-point (0.04, 7.5) or 4.0-point (0.5, 7.5) higher behavioral symptoms index composite score. In models evaluating effect modification by sex, a 10-fold increase in E1 was associated with a 4.3-point (1.2, 7.4) decrease in adaptive skills composite score in girls only (interaction p = 0.04). We observed associations between testosterone and internalizing behaviors and behavioral symptoms index in both sexes, as well as a female-specific association between E1 and adaptive skills. Sex hormones during pregnancy may play a key role in influencing later-life behavior, and additional studies should further examine different periods of susceptibility to hormonal signals.

2D:4D Suggests a Role of Prenatal Testosterone in Gender Dysphoria

Gender dysphoria (GD) reflects distress caused by incongruence between one's experienced gender identity and one's natal (assigned) gender. Previous studies suggest that high levels of prenatal testosterone (T) in natal females and low levels in natal males might contribute to GD. Here, we investigated if the 2D:4D digit ratio, a biomarker of prenatal T effects, is related to GD. We first report results from a large Iranian sample, comparing 2D:4D in 104 transwomen and 89 transmen against controls of the same natal sex. We found significantly lower (less masculine) 2D:4D in transwomen compared to control men. We then conducted random-effects meta-analyses of relevant studies including our own (k = 6, N = 925 for transwomen and k = 6, N = 757 for transmen). In line with the hypothesized prenatal T effects, transwomen showed significantly feminized 2D:4D (d ≈ 0.24). Conversely, transmen showed masculinized 2D:4D (d ≈ - 0.28); however, large unaccounted heterogeneity across studies emerged, which makes this effect less meaningful. These findings support the idea that high levels of prenatal T in natal females and low levels in natal males play a part in the etiology of GD. As we discuss, this adds to the evidence demonstrating the convergent validity of 2D:4D as a marker of prenatal T effects.

Basic Human Body Dimensions Relate to Alcohol Dependence and Predict Hospital Readmission

Alcohol dependence is a severe mental illness and there is a need for more effective preventive and therapeutic strategies. Translational research suggests that intrauterine sex hormone exposure modulates the risk and course of alcohol dependence during adulthood. During development, sex hormones permanently shape sexually dimorphic body dimensions. Thus, these dimensions may provide insight into sex hormone organization. Here, we compared body measurements (absolute, relative to, and residualized on height) between 200 alcohol-dependent in-patients and 240 age-matched healthy control subjects and investigated how these measurements associate with the patients' prospective 12- and 24-month outcome. The results show that alcohol dependence is related to lower absolute, relative, and residualized body measurements for height and weight, head circumference, bitragion head arc, lip-chin distance, hip, thigh, and calf circumference, and foot length and breadth. In male alcohol-dependent in-patients, higher risk, shorter latency, and more alcohol-related readmissions were predicted by higher absolute, relative, and residualized thigh and calf circumferences. The second-to-fourth finger length ratio, a putative proxy for prenatal sex hormone organization, was not convincingly correlated with the body dimensions, suggesting that the results represent pubertal (or later) effects. The study's findings have implications for further research. The body measurements' high accessibility may facilitate the future transition into clinical settings.

Risk-taking behavior, the second-to-fourth digit ratio and psychological features in a sample of cavers

Background

The risk-taking behavior is largely modulated by the subject's history, its lifestyles, by the characteristics of the situations with which it is compared, and also by the effects of prenatal androgens. Thus, the personality of the single person is a significant predictor of such way of acting.

Methods

The present study aimed to explore the relationship between Digit Ratio Measurement (2D:4D) and personality factors capable to be good predictors for choosing highly risky activities, such as caving. Furthermore, our purpose was to investigate whether 2D:4D ratio is related to cavers' affective states and to assess the personological and emotional features of 34 healthy cavers, aged between 24 and 71 years (M = 39.70, SD = 9.81).

Results

Data analysis showed several significant correlations between 2D:4D and Deliberate Risk Taking (RTI) and Precautionary Behavior (RTI), confirming that 2D:4D is a reliable index able to predict risk-taking behaviors. Furthermore, data analysis showed that Conscientiousness and its sub-dimension Scrupulousness (BFQ-2) are recurrent among significant correlations; in particular, the latter reports negative correlations with many factors of POMS. Moreover, all participants seemed to have a good attitude to collaboration, in terms of goal-direct strategy, and an adequate management of negative affective states, useful to maintaining a good level of stress within the group. Finally, the BFQ-2 factor Openness to culture seemed to be a predominant feature in the cavers, and this feature could be considered as predictive in the choice of an activity, such as caving, which requires curiosity, perseverance and a great planning of cave exploration.

Opposite-sex and same-sex twin studies of physiological, cognitive and behavioral traits

A scientific interest in opposite-sex (OS) twins comes from animal studies showing hormone transfer between fetuses in utero. A parallel effect in humans may occur, especially for OS females who may be exposed to androgens, in particular testosterone, from the male co-twin. Conversely, OS males may be exposed to lower levels of prenatal testosterone than do same-sex (SS) males. In this special issue, we reviewed published studies investigating potential differences between OS and SS twins in physiological, cognitive and behavioral traits focusing on the Twin Testosterone Transfer (TTT) hypothesis. Sixty articles fulfilled the eligibility criteria including 23 studies published since the review by Tapp et al. (2011). In general, studies of cognition are conflicting, but it is the phenotype for which most support for the TTT hypothesis is found. Less consistent evidence has been found regarding physiological and behavioral traits. We hope that this special issue will stimulate a discussion about how an investigation of the TTT hypothesis should continue in future research.

The biological basis of sexual orientation: How hormonal, genetic, and environmental factors influence to whom we are sexually attracted

Humans develop relatively stable attractions to sexual partners during maturation and present a spectrum of sexual orientation from homosexuality to heterosexuality encompassing varying degrees of bisexuality, with some individuals also displaying asexuality. Sexual orientation represents a basic life phenomenon for humans. However, the molecular mechanisms underlying these diverse traits of sexual orientation remain highly controversial. In this review, we systematically discuss recent advancements in sexual orientation research, including those related to measurements and associated brain regions. Current findings regarding sexual orientation modulation by hormonal, genetic, maternal immune system, and environmental factors are summarized in both human and model systems. We also emphasize that future studies should recognize the differences between males and females and pay more attention to minor traits and the epigenetic regulation of sexual orientation. A comprehensive view of sexual orientation may promote our understanding of the biological basis of sex, and that of human reproduction, and evolution.

Digit ratio (2D : 4D) and prosocial behaviour in economic games: no direct correlation with generosity, bargaining or trust-related behaviours

Prenatal exposure to sex hormones exerts organizational effects on the brain which have observable behavioural correlates in adult life. There are reasons to expect that social behaviours-fundamental for the evolutionary success of humans-might be related to biological factors such as prenatal sex hormone exposure. Nevertheless, the existing literature is inconclusive as to whether and how prenatal exposure to testosterone and oestrogen, proxied by the second-to-fourth digit ratio (2D : 4D), may predict non-selfish behaviour. Here, we investigate this question using economic experiments with real monetary stakes and analyse five different dimensions of social behaviour in a comparatively large sample of Caucasian participants (n = 560). For both males and females, our results show no robust association between right- or left-hand 2D : 4D and generosity, bargaining or trust-related behaviours. Moreover, no differences in behaviour were found according to sex. We conclude that there is no direct correlation between 2D : 4D and these social behaviours.

Early-life triclosan exposure and parent-reported behavior problems in 8-year-old children

BACKGROUND

Triclosan exposure may decrease circulating thyroxine levels or cause neuron apoptosis, which in turn may adversely affect neurodevelopment. However, few studies have examined the association of early life triclosan exposure with child behavior.

OBJECTIVE

To quantify the association between early-life triclosan exposure and child behavior at age 8-years in 202 mother-child pairs from the HOME study (Cincinnati, OH; enrolled: 2003-2006).

METHODS

We quantified urinary triclosan concentrations up to 3 times in mothers (16-weeks, 26-weeks, and delivery) and up to 6 times in children (1, 2, 3, 4, 5, and 8 years). Parents rated children's problem behaviors at age 8-years using the Behavioral Assessment System for Children-2 (BASC-2). Adjusting for covariates and accounting for exposure measurement error, we estimated changes in behavior problem scores per 10-fold increase in mean gestational and childhood triclosan concentrations. In addition, we estimated sex-specific associations.

RESULTS

Child sex modified the association of gestational and childhood triclosan with several BASC-2 scales (sex × triclosan p-values < 0.2). In boys, increasing gestational triclosan was associated with higher behavioral symptom index (β: 4.5; 95% CI: 1.0, 8.1), externalizing problems (β: 5.0; 95% CI: 1.2, 9.0), attention problem (β: 6.6; 95% CI: 2.4, 11), hyperactivity (β: 6.4; 95% CI: 2.1, 11), and somatization (β: 3.8; 95% CI: 0.3, 7.3) scores. In contrast, triclosan-BASC-2 associations in girls were generally null and not statistically significant. We observed similar patterns of associations between childhood triclosan and these same behavioral scores; however, their magnitude decreased substantially after adjusting for gestational triclosan and associations were not statistically significant.

CONCLUSION

In this cohort, increasing gestational and childhood urinary triclosan concentrations were associated with higher behavior problem scores in 8-year old boys, but not girls.

Is digit ratio (2D:4D) associated with the choice for the uniformed versus a civil study course by the Polish youth?

The 2nd to 4th digit ratio (2D:4D) is a sexually dimorphic trait determined by the relative balance of prenatal testosterone (T) and oestrogen during the intrauterine development of foetus. Males on average have relatively lower 2D:4D than women in population. Lower 2D:4D is very often linked with greater physical ability, strength, superior sporting performance and many personality traits and behaviours which are seen more among the males. Recently, lower 2D:4D were associated with military and police services among the Polish women. The objectives of this study were to examine whether 2D:4D differed between the students of a study course for future military service and a civil study course and whether sex difference in this ratio is present in both these groups. The cross sectional study included 50 boys and 42 girls enrolled in the uniformed course and other 56 boys and 50 girls of a general course in an upper-secondary School. The lengths of the second (2D) and fourth fingers (4D) of each hand were measured to have the 2D:4D ratio. Height and weight were also recorded. Overall, as well as among the civil course students, males showed significantly lower mean 2D:4D compared to the females. But there was no significant sex difference in digit ratio among the uniformed course students. Besides, the females under uniformed course showed lower 2D:4D than the females in civil course, whereas, the male uniformed students had similar or almost same 2D:4D values with the male civil course students. Increased prenatal testosterone exposure might have a role in determining the choice towards a challenging future occupation and such effect is perhaps more pronounced in women than in males.