Biomarker For Prenatal Androgen Exposure Research Articles

Investigating the effects of prenatal testosterone exposure (via 2D:4D) and socio-relational factors on 3–6-year-old preschoolers' prosocial choices

Background and aimsProsocial behavior such as helping and sharing develops early in childhood. Yet very few studies have investigated physiological and relational factors shaping prosociality among children. Here, we systematically examined the role of prenatal androgen exposure alongside prestige, dominance, and friendship in 3–6-year-old preschoolers' prosocial sharing with familiar peers. MethodsWe tested a sample of 65 children, predominately of European descent. We used a cost-free direct-interaction prosocial choice task to assess children's prosocial tendencies. Second-to-fourth digit ratio (2D:4D) was used as a retrospective biomarker for prenatal androgen exposure. Prestige was measured through behavioral observations of interaction partners and visual regard, dominance through teacher questionnaires, and friendship via peer preference assessments. ResultsWe found that children acted prosocially when tested with a familiar peer. Children with lower 2D:4D (higher prenatal androgen exposure) behaved more prosocially. Further, there were marginal associations between the donors' prosocial tendencies and their visual regard as a proxy of their prestige (positive effect) and their teacher-rated dominance relative to the recipient (negative effect). Neither age, sex, nor friendship influenced prosocial choices. ConclusionsPrenatal androgen exposure, approximated via 2D:4D, was associated with prosocial behavior. In contrast to previous research in older children, higher exposure was related to stronger prosocial tendencies, which corresponds to earlier findings on fairness in adults. Our findings point towards a potential role of sex steroids in the early development of children's social behavior, but they have to be interpreted with caution due to the small sample size of the current study. Nevertheless, they underscore the importance of integrating biological and psychological perspectives, while also highlighting the significance of studying the development of prosocial behavior within peer groups.

Handgrip strength and 2D : 4D in women: homogeneous samples challenge the (apparent) gender paradox.

The length ratio between the second and the fourth digit (2D : 4D) is a retrospective, non-invasive biomarker for prenatal androgen exposure. It was found to be negatively correlated with handgrip strength (HGS) in men, but the evidence for women is mixed. Such studies in women call for increased detection sensitivity. The present study was designed to reduce potential confounding factors, especially age and ethnicity variation. We measured the digit ratios and HGS of 125 healthy women between 19 and 31 years of age from a remote region in Austria. 2D : 4D of both hands was significantly and negatively correlated with HGS (n = 125, right hand: r = –0.255, p = 0.002, left hand: r = –0.206, p = 0.011). Size, direction and significance of correlation coefficients remained stable when statistically controlling for age, body weight, body height, body mass index or hours of exercise per week. This yields theory-consistent evidence that HGS and 2D : 4D are clearly associated in women—when sufficiently reducing genetic variation (confounding 2D : 4D), the ontogenetic environment and age ranges (confounding HGS) in the study population. This finding implies similar organizing effects of prenatal androgens as in men, pointing to a more parsimonious developmental mechanism and a new look into its proximate and ultimate causes.

No evidence for a difference in 2D:4D ratio between youth with elevated prenatal androgen exposure due to congenital adrenal hyperplasia and controls

The second-to-fourth digit ratio (2D:4D) has been associated with sexual dimorphism, with a lower 2D:4D in males. A large body of research has relied on the 2D:4D as a proxy for prenatal androgen exposure, and includes reports of relationships between 2D:4D and a wide range of human traits. Here, we examine the validity of the 2D:4D proxy by studying the association between 2D:4D and classical Congenital Adrenal Hyperplasia (CAH) due to 21-hydroxylase deficiency, a condition characterized by excessive prenatal exposure to androgens during most of the gestational period. To this end, we retrospectively examine 513 serial radiographs of the left hand obtained clinically in 90 youth with classical CAH (45 female) and 70 control youth (31 female). Replicating previous reports, we observe associations of the 2D:4D with sex (lower 2D:4D in males) and age (increase of 2D:4D through development). However, we find no evidence for differences in 2D:4D between CAH and controls (full sample: β = −0.001 (−0.008, 0.006); females: β = −0.004 [−0.015, 0.007]; males: β = 0.001, [−0.008, 0.011]). Although our findings do not rule out a small association between the 2D:4D and CAH, they cast doubt on the usefulness of the 2D:4D as a biomarker for prenatal androgen exposure in behavioral research.

Sex Differences in Rhesus Monkeys' Digit Ratio (2D:4D Ratio) and Its Association With Maternal Social Dominance Rank.

Prenatal androgen exposure (PAE) plays a pivotal role in masculinizing the developing body and brain, and extreme exposure may contribute to autism, anxiety disorder and schizophrenia. One commonly used biomarker for PAE is the pointer-to-ring-finger digit length (2D:4D) ratio. Although this biomarker is widely used in human studies, relatively few studies have investigated 2D:4D ratio in nonhuman primates, particularly rhesus macaques (Macaca mulatta), one of the most commonly used animals in biomedical research. Thus far, data suggest that sexual dimorphism in 2D:4D ratio may be in the opposite direction in some monkey species, when compared to the pattern exhibited by humans and great apes. Using a large sample size, we investigated whether rhesus monkeys’ 2D:4D ratio shows the same sex-differentiated pattern present in other Old World monkey species. We also investigated whether individual differences in 2D:4D ratio are associated with the social dominance rank of subjects’ mothers during pregnancy, and the social dominance rank the subjects attained as adults. Subjects were 335 rhesus monkeys between 3 years and 24 years of age (M = 6.6). Maternal dominance rank during pregnancy and subjects’ adult dominance rank were categorized into tertiles (high, middle and low). Results showed that, across both hands, male rhesus monkeys exhibited higher 2D:4D ratio than females, a pattern consistent with other monkey species and a reversal from the pattern typically observed in humans and apes. This sex difference was modulated by maternal dominance rank, with female offspring of high-ranking and middle-ranking mothers exhibiting masculinized 2D:4D ratio, indicating that maternal dominance rank during pregnancy may influence levels of PAE. There was no association between subjects’ 2D:4D ratio and the social dominance rank they attained as adults. These findings show a consistent sex difference in Old World monkeys’ 2D:4D ratio that diverges from the pattern observed in apes and humans, and suggest maternal social dominance rank modulates PAE in rhesus monkeys.

Anogenital distance and reproductive outcomes in 9- to 11-year-old boys: the INMA-Granada cohort study.

Studies examining the association of anogenital distance (AGD), a biomarker of prenatal androgen exposure, with sexual development in children are lacking. To assess the association between AGD measures and reproductive outcomes, including puberty onset, testicular volume, reproductive hormone levels, and urogenital malformations in boys aged 9-11years. A cross-sectional study was conducted among children belonging to the Spanish Environment and Childhood (INMA) Project, a population-based birth cohort study. The present sample included 279 boys for whom data were available on AGD, pubertal stage, testicular volume, and relevant covariates. Out of the boys with AGD data, 187 provided a blood sample for hormone analysis. AGD was measured from the center of the anus to the base of the scrotum. Pubertal development was assessed according to Tanner stage of genital development (G1-G5), and testicular volume was measured with an orchidometer. After adjusting for potential confounders, logistic regression analysis showed that AGD was positively associated with testicular volume but not with Tanner stage (>G1 vs. G1), serum hormone levels, or undescended testis. Regardless of their age, body mass index, and Tanner stage (G1 or >G1), boys with longer AGD showed increased odds of a testicular volume >3mL (OR=1.06, 95%CI=1.00-1.19 per 10% increment in AGD; and OR=3.14, 95%CI=0.99-9.94 for AGD >42 mm vs. <33mm). Longer AGD was associated with testicular growth, an indicator of gonadarche, but not with other reproductive outcomes. Although AGD was positively associated with testicular volume, it remains unclear whether AGD predicts testis size at puberty or is related to puberty onset.

Genome-wide association study identifies nine novel loci for 2D:4D finger ratio, a putative retrospective biomarker of testosterone exposure in utero.

The ratio of the length of the index finger to that of the ring finger (2D:4D) is sexually dimorphic and is commonly used as a non-invasive biomarker of prenatal androgen exposure. Most association studies of 2D:4D ratio with a diverse range of sex-specific traits have typically involved small sample sizes and have been difficult to replicate, raising questions around the utility and precise meaning of the measure. In the largest genome-wide association meta-analysis of 2D:4D ratio to date (N = 15 661, with replication N = 75 821), we identified 11 loci (9 novel) explaining 3.8% of the variance in mean 2D:4D ratio. We also found weak evidence for association (β = 0.06; P = 0.02) between 2D:4D ratio and sensitivity to testosterone [length of the CAG microsatellite repeat in the androgen receptor (AR) gene] in females only. Furthermore, genetic variants associated with (adult) testosterone levels and/or sex hormone-binding globulin were not associated with 2D:4D ratio in our sample. Although we were unable to find strong evidence from our genetic study to support the hypothesis that 2D:4D ratio is a direct biomarker of prenatal exposure to androgens in healthy individuals, our findings do not explicitly exclude this possibility, and pathways involving testosterone may become apparent as the size of the discovery sample increases further. Our findings provide new insight into the underlying biology shaping 2D:4D variation in the general population.

Digit Ratio (2D:4D) Predicts Self-Reported Measures of General Competitiveness, but Not Behavior in Economic Experiments.

The ratio of index finger length to ring finger length (2D:4D) is considered to be a putative biomarker of prenatal androgen exposure (PAE), with previous research suggesting that 2D:4D is associated with human behaviors, especially sex-typical behaviors. This study empirically examines the relationship between 2D:4D and individual competitiveness, a behavioral trait that is found to be sexually dimorphic. We employ two related, but distinct, measures of competitiveness, namely behavioral measures obtained from economic experiments and psychometric self-reported measures. Our analyses are based on two independent data sets obtained from surveys and economic experiments with 461 visitors of a shopping mall (Study I) and 617 university students (Study II). The correlation between behavior in the economic experiment and digit ratios of both hands is not statistically significant in either study. In contrast, we find a negative and statistically significant relationship between psychometric self-reported measures of competitiveness and right hand digit ratios (R2D:4D) in both studies. This relationship is especially strong for younger people. Hence, this study provides some robust empirical evidence for a negative association between R2D:4D and self-reported competitiveness. We discuss potential reasons why digit ratio may relate differently to behaviors in specific economics experiments and to self-reported general competitiveness.

Do sex differences in CEOAEs and 2D:4D ratios reflect androgen exposure? A study in women with complete androgen insensitivity syndrome

BackgroundStudies investigating the influence of perinatal hormone exposure on sexually differentiated traits would greatly benefit from biomarkers of these early hormone actions. Click-evoked otoacoustic emissions show sex differences that are thought to reflect differences in early androgen exposure. Women with complete androgen insensitivity syndrome (CAIS), who lack androgen action in the presence of XY-chromosomes, enabled us to study the effect of complete androgen inaction. The main goal was to investigate a possible link between click-evoked otoacoustic emissions and effective androgen exposure and, thus, whether this can be used as a biomarker. In addition, we aimed to replicate the only previous 2nd vs 4th digit-ratio study in women with CAIS, because despite the widely expressed criticisms of the validity of this measure as a biomarker for prenatal androgen exposure, it still is used for this purpose.MethodsClick-evoked otoacoustic emissions and digit ratios from women with CAIS were compared to those from control men and women.ResultsThe typical sex differences in click-evoked otoacoustic emissions and digit ratios were replicated in the control groups. Women with CAIS showed a tendency towards feminine, i.e., larger, click-evoked otoacoustic emission amplitudes in the right ear, and a significant female-typical, i.e., larger, digit ratio in the right hand. Although these results are consistent with androgen-dependent development of male-typical click-evoked otoacoustic emission amplitude and 2nd to 4th digit ratios, the within-group variability of these two measures was not reduced in women with CAIS compared with control women.ConclusionsIn line with previous studies, our findings in CAIS women suggest that additional, non-androgenic, factors mediate male-typical sexual differentiation of digit ratios and click-evoked otoacoustic emissions. Consequently, use of these measures in adults as retrospective markers of early androgen exposure is not recommended.

Anogenital Distance, a Biomarker of Prenatal Androgen Exposure Is Associated With Prostate Cancer Severity.

Anogenital distance (AGD), the distance from the centre of the anus to the genitals, is a sexually dimorphic phenotype in mammals. Experimental studies have shown that AGD is a biomarker of prenatal androgen exposure during the masculinisation period of development. The aim of this study is to assess the relationship between anogenital distance (AGD), as an indirect marker of prenatal hormonal environment, and prostate cancer (PCa) severity. We conducted a cross-sectional study with a total of 120 PCa patients with confirmed biopsy of the tumour from April 2007 to July 2015. Two variants of the anogenital distance were assessed, from the anus to the posterior base of the scrotum (AGDAS ) and to the cephalad insertion of the penis (AGDAP ). We compared differences in groups to evaluate the association between AGD measurements and severity of the preoperative biopsy and clinical scores. Longer AGDAS was significantly associated with the highest Gleason score (P = 0.015) and D'Amico nomogram (P = 0.048). In contrast, no statistical differences were found in the AGDAP and severity of the preoperative biopsy. These findings are consistent with the hypothesis that a higher prenatal androgen exposure is associated with higher severity of PCa. Prostate 77: 406-411, 2017. © 2016 Wiley Periodicals, Inc.

2D:4D indicates phimosis risk: A study on digit ratio and early foreskin development

BackgroundMany researchers have adopted 2D:4D (second to fourth finger length ratio) as a noninvasive retrospective biomarker for prenatal androgen exposure in recent years. It is thought to be related to diverse traits including behavioral phenotypes, disease susceptibility, and development of urogenital system. ObjectiveTo examine the relationship between 2D:4D and early foreskin development. MethodsWe analyzed the digit ratio and foreskin condition in 176 cases (range 0–6years). The boys were divided into four groups according to their ages: group 1, neonates (below 28days, n=13); group 2, infants (1–12months, n=45); group 3, toddlers (1–2years old, n=42); group 4, preschool children (3–6years old, n=76). We measured the lengths of the second and fourth digits of the left and right hands. The foreskin status was classified into 4 types. Type I (phimosis), type II (partial phimosis), type III (adhesion of prepuce), type IV (normal). ResultsThe phimosis rate was 92.3%, 82.2%, 45.2%, and 38.7% in group 1 to group 4. In contrast, the proportion of normal foreskin increased from 0% in neonates to 13.2% in preschool children. The percentage of higher level of foreskin development shows a downward trend with the increase of digits ratio, and as the age grows, the percentage of normal foreskin cases also increases. ConclusionsThese results suggest that a higher R2D:4D (right hand 2D:4D) is a risk factor for phimosis in the early human development. Age is also a significant influence factor of foreskin conditions. Additional research is required to identify pathophysiologic mechanisms and to determine clinical significance.

Interpreting digit ratio (2D:4D)–behavior correlations: 2D:4D sex difference, stability, and behavioral correlates and their replicability in young children

The popularity of using the ratio of the second to the fourth digit (2D:4D) to study influences of early androgen exposure on human behavior relies, in part, on a report that the ratio is sex-dimorphic and stable from age 2 years (Manning etal., 1998). However, subsequent research has rarely replicated this finding. Moreover, although 2D:4D has been correlated with many behaviors, these correlations are often inconsistent. Young children's 2D:4D–behavior correlations may be more consistent than those of older individuals, because young children have experienced fewer postnatal influences. To evaluate the usefulness of 2D:4D as a biomarker of prenatal androgen exposure in studies of 2D:4D–behavior correlations, we assessed its sex difference, temporal stability, and behavioral correlates over a 6- to 8-month period in 126, 2- to 3-year-old children, providing a rare same-sample replicability test. We found a moderate sex difference on both hands and high temporal stability. However, between-sex overlap and within-sex variability were also large. Only 3 of 24 correlations with sex-typed behaviors—scores on the Preschool Activities Inventory (PSAI), preference for a boy-typical toy, preference for a girl-typical toy, were significant and in the predicted direction, all of which involved the PSAI, partially confirming findings from another study. Correlation coefficients were larger for behaviors that showed larger sex differences. But, as in older samples, the overall pattern showed inconsistency across time, sex, and hand. Therefore, although sex-dimorphic and stable, 2D:4D–behavior correlations are no more consistent for young children than for older samples. Theoretical and methodological implications are discussed.

First trimester phthalate exposure and anogenital distance in newborns.

Is first trimester phthalate exposure associated with anogenital distance (AGD), a biomarker of prenatal androgen exposure, in newborns? Concentrations of diethylhexyl phthalate (DEHP) metabolites in first trimester maternal urine samples are inversely associated with AGD in male, but not female, newborns. AGD is a sexually dimorphic measure reflecting prenatal androgen exposure. Prenatal phthalate exposure has been associated with shorter male AGD in multiple animal studies. Prior human studies, which have been limited by small sample size and imprecise timing of exposure and/or outcome, have reported conflicting results. The Infant Development and the Environment Study (TIDES) is a prospective cohort study of pregnant women recruited in prenatal clinics in San Francisco, CA, Minneapolis, MN, Rochester, NY and Seattle, WA in 2010-2012. Participants delivered 787 infants; 753 with complete data are included in this analysis. Any woman over 18 years old who was able to read and write English (or Spanish in CA), who was <13 weeks pregnant, whose pregnancy was not medically threatened and who planned to deliver in a study hospital was eligible to participate. Analyses include all infants whose mothers provided a first trimester urine sample and who were examined at or shortly after birth. Specific gravity (SpG) adjusted concentrations of phthalate metabolites in first trimester urine samples were examined in relation to genital measurements. In boys (N = 366), we obtained two measures of anogenital distance (AGD) (anoscrotal distance, or AGDAS and anopenile distance, AGDAP) as well as penile width (PW). In girls (N = 373), we measured anofourchette distance (AGDAF) and anoclitoral distance (AGDAC). We used multivariable regression models that adjusted for the infant's age at exam, gestational age, weight-for-length Z-score, time of day of urine collection, maternal age and study center. Three metabolites of DEHP were significantly and inversely associated with both measures of boys' AGD. Associations (β, 95% confidence interval (CI)) between AGDAS and (log10) SpG-adjusted phthalate concentrations were: -1.12 (-2.16, -0.07) for mono-2-ethylhexyl phthalate (MEHP), -1.43, (-2.49, -0.38) for mono-2-ethyl-5-oxohexyl phthalate (MEOHP), and -1.28 (-2.29, -0.27) for mono-2-ethyl-5-hydroxyhexyl (MEHHP). Associations were of similar magnitude for AGDAP. Associations were weaker and not statistically significant for PW. No other phthalate metabolites were associated with any genital measurement in boys. No phthalate metabolites were associated with either AGD measure in girls. Exposure assessment was based on a single first trimester urine sample, which may have introduced exposure misclassification. In addition, significant between-center differences suggest that this measurement is difficult to standardize. Our findings are consistent with multiple rodent studies and most human studies which were far smaller. The data we report here suggest that even at current low levels, environmental exposure to DEHP can adversely affect male genital development resulting in reproductive tract changes that may impact reproductive health later in life. These findings have important implications for public policy since most pregnant women are exposed to this ubiquitous chemical. Funding for TIDES was provided by the following grants from the National Institute of Environmental Health Sciences: R01ES016863-04 and R01 ES016863-02S4. The authors report no conflict of interest.

Evidence for Sexually Dimorphic Associations Between Maternal Characteristics and Anogenital Distance, a Marker of Reproductive Development

Data from animal models, historical cohorts, and modern epidemiologic studies have suggested that maternal characteristics can affect reproductive health of offspring; however, distinguishing between prenatal and postnatal contributions is difficult. Anogenital distance (AGD), the distance from the anus to the genitals, is believed to be a biomarker of prenatal androgen exposure in many species, and in humans it has been associated with several adult reproductive health outcomes. We used data from a pregnancy cohort study conducted in 4 US cities from 1999-2005 to examine whether AGD measurements in infants were associated with maternal self-reported age at conception, age at menarche, age at first birth, parity, and gravidity. AGD was measured in 289 infants (140 male, 149 female) born to study participants. After adjustment for relevant covariates, in linear regression models stratified by infant sex, maternal age was positively associated with AGD in male infants (AGD, anus to penis: β = 0.50, P = 0.002; AGD, anus to scrotum: β = 0.29, P = 0.02) but not female infants. Parity was inversely associated with AGD (anus to scrotum; β = -1.68, P = 0.03) in male infants. No other maternal characteristic predicted AGD in either sex. The mechanism underlying the unexpected relationship between maternal characteristics and AGD is unknown; however, we suggest several possibilities for future study.

Finger length pattern as a biomarker for prenatal androgen exposure and the risk for osteoarthritis and pain

Finger length pattern as a biomarker for prenatal androgen exposure and the risk for osteoarthritis and pain

Prenatal exposure to stressful life events is associated with masculinized anogenital distance (AGD) in female infants

In animal models, prenatal stress programs reproductive development in the resulting offspring, however little is known about effects in humans. Anogenital distance (AGD) is a commonly used, sexually dimorphic biomarker of prenatal androgen exposure in many species. In rodents, prenatally stressed males have shorter AGD than controls (suggesting lower prenatal androgen exposure), whereas prenatally stressed females have longer AGD than controls (suggesting greater prenatal androgen exposure). Our objective was to investigate the relationship between stressful life events in pregnancy and infant AGD. In a prospective cohort study, pregnant women and their partners reported exposure to stressful life events during pregnancy. Pregnancies in which the couple reported 4+ life events were considered highly stressed. After birth (average 16.5months), trained examiners measured AGD in the infants (137 males, 136 females). After adjusting for age, body size and other covariates, females born to couples reporting high stress had significantly longer (i.e. more masculine) AGD than females born to couples reporting low stress (p=0.015). Among males, high stress was weakly, but not significantly, associated with shorter AGD. Our results suggest prenatal stress may masculinize some aspects of female reproductive development in humans. More sensitive measures of prenatal stress and additional measures of reproductive development are needed to better understand these relationships and clarify mechanisms.

Differential Correlations of Digit Ratio (2D:4D) with Aggressive Dominance and Sociable Dominance Are Not Demonstrated: Commentary on van der Meij, Almela, Buunk, Dubbs, and Salvador (2012, Aggressive Behavior, 38(3), 208–212)

Van der Meij, Almela, Buunk, Dubbs, and Salvador reported that, among young men (N = 84), a putative biomarker for prenatal androgen exposure (second-to-fourth digit ratio; 2D:4D) correlated negatively to self-reported aggressive dominance, but not to sociable dominance. A critical examination of this allegedly differential effect shows it to be unsupported and unlikely to be replicable. Statistical power of the sample was so low that the nominally significant correlation coefficient with aggressive dominance and the nominally not significant one with sociable dominance actually did not differ significantly from each other. Apart from these data-analytic and statistical power issues, a number of further substantive comments are raised, including conceptual and study design issues, 2D:4D measurement and reliability issues, and biased presentation (i.e. selective citation) of prior related research evidence. More generally, it is suggested that 2D:4D research would benefit from adopting publishing standards requiring discovery and replication samples (i.e. successful replication of novel findings by the initial researchers themselves), as is now increasingly required for publishing in various fields of inconsistent, hard-to-replicate evidence.

A Variant in LIN28B Is Associated with 2D:4D Finger-Length Ratio, a Putative Retrospective Biomarker of Prenatal Testosterone Exposure

The ratio of the lengths of an individual's second to fourth digit (2D:4D) is commonly used as a noninvasive retrospective biomarker for prenatal androgen exposure. In order to identify the genetic determinants of 2D:4D, we applied a genome-wide association approach to 1507 11-year-old children from the Avon Longitudinal Study of Parents and Children (ALSPAC) in whom 2D:4D ratio had been measured, as well as a sample of 1382 12- to 16-year-olds from the Brisbane Adolescent Twin Study. A meta-analysis of the two scans identified a single variant in the LIN28B gene that was strongly associated with 2D:4D (rs314277: p = 4.1 x 10(-8)) and was subsequently independently replicated in an additional 3659 children from the ALSPAC cohort (p = 1.53 x 10(-6)). The minor allele of the rs314277 variant has previously been linked to increased height and delayed age at menarche, but in our study it was associated with increased 2D:4D in the direction opposite to that of previous reports on the correlation between 2D:4D and age at menarche. Our findings call into question the validity of 2D:4D as a simplistic retrospective biomarker for prenatal testosterone exposure.