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Sakaguchi K, Tawata S. Giftedness and atypical sexual differentiation: enhanced perceptual functioning through estrogen deficiency instead of androgen excess. Front Endocrinol (Lausanne) 2024; 15:1343759. [PMID: 38752176 PMCID: PMC11094242 DOI: 10.3389/fendo.2024.1343759] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/24/2023] [Accepted: 04/15/2024] [Indexed: 05/18/2024] Open
Abstract
Syndromic autism spectrum conditions (ASC), such as Klinefelter syndrome, also manifest hypogonadism. Compared to the popular Extreme Male Brain theory, the Enhanced Perceptual Functioning model explains the connection between ASC, savant traits, and giftedness more seamlessly, and their co-emergence with atypical sexual differentiation. Overexcitability of primary sensory inputs generates a relative enhancement of local to global processing of stimuli, hindering the abstraction of communication signals, in contrast to the extraordinary local information processing skills in some individuals. Weaker inhibitory function through gamma-aminobutyric acid type A (GABAA) receptors and the atypicality of synapse formation lead to this difference, and the formation of unique neural circuits that process external information. Additionally, deficiency in monitoring inner sensory information leads to alexithymia (inability to distinguish one's own emotions), which can be caused by hypoactivity of estrogen and oxytocin in the interoceptive neural circuits, comprising the anterior insular and cingulate gyri. These areas are also part of the Salience Network, which switches between the Central Executive Network for external tasks and the Default Mode Network for self-referential mind wandering. Exploring the possibility that estrogen deficiency since early development interrupts GABA shift, causing sensory processing atypicality, it helps to evaluate the co-occurrence of ASC with attention deficit hyperactivity disorder, dyslexia, and schizophrenia based on phenotypic and physiological bases. It also provides clues for understanding the common underpinnings of these neurodevelopmental disorders and gifted populations.
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Affiliation(s)
- Kikue Sakaguchi
- Research Department, National Institution for Academic Degrees and Quality Enhancement of Higher Education (NIAD-QE), Kodaira-shi, Tokyo, Japan
| | - Shintaro Tawata
- Graduate School of Human Sciences, Sophia University, Chiyoda-ku, Tokyo, Japan
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2
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Lenz B, Gerhardt S, Boroumand-Jazi R, Eichler A, Buchholz VN, Fasching PA, Kornhuber J, Banaschewski T, Flor H, Guldner S, Prignitz M, Nees F. Sex-specific association between prenatal androgenization (second-to-fourth digit length ratio) and frontal brain volumes in adolescents. Eur Arch Psychiatry Clin Neurosci 2023; 273:1243-1254. [PMID: 36449103 PMCID: PMC10449726 DOI: 10.1007/s00406-022-01515-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/04/2022] [Accepted: 10/26/2022] [Indexed: 12/03/2022]
Abstract
Prenatal androgenization associates sex-dependently with behavior and mental health in adolescence and adulthood, including risk-taking, emotionality, substance use, and depression. However, still little is known on how it affects underlying neural correlates, like frontal brain control regions. Thus, we tested whether prenatal androgen load is sex-dependently related to frontal cortex volumes in a sex-balanced adolescent sample. In a cross-sectional magnetic resonance imaging study, we examined 61 adolescents (28 males, 33 females; aged 14 or 16 years) and analyzed associations of frontal brain region volumes with the second-to-fourth digit length ratio (2D:4D), an established marker for prenatal androgenization, using voxel-based morphometry in a region-of-interest approach. Lower 2D:4D (indicative of higher prenatal androgen load) correlated significantly with smaller volumes of the right anterior cingulate cortex (r-ACC; β = 0.45) in male adolescents and with larger volumes of the left inferior frontal gyrus orbital part (l-IFGorb; β = - 0.38) in female adolescents. The regression slopes of 2D:4D on the r-ACC also differed significantly between males and females. The study provides novel evidence that prenatal androgenization may influence the development of the frontal brain in a sex- and frontal brain region-specific manner. These effects might contribute to the well-known sex differences in risk-taking, emotionality, substance use, and depression. Future research is needed to elucidate the role of prenatal androgenization within the biopsychosocial model.
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Affiliation(s)
- Bernd Lenz
- Department of Addictive Behavior and Addiction Medicine, Central Institute of Mental Health (CIMH), Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany.
- Department of Psychiatry and Psychotherapy, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany.
| | - Sarah Gerhardt
- Department of Addictive Behavior and Addiction Medicine, Central Institute of Mental Health (CIMH), Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
| | - Rafat Boroumand-Jazi
- Department of Addictive Behavior and Addiction Medicine, Central Institute of Mental Health (CIMH), Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
| | - Anna Eichler
- Department of Child and Adolescent Mental Health, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Verena Nadine Buchholz
- Department of Psychiatry and Psychotherapy, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Peter A Fasching
- Department of Obstetrics and Gynecology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Johannes Kornhuber
- Department of Psychiatry and Psychotherapy, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Tobias Banaschewski
- Department of Child and Adolescent Psychiatry and Psychotherapy, Central Institute of Mental Health (CIMH), Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
| | - Herta Flor
- Institute of Cognitive and Clinical Neuroscience, Central Institute of Mental Health (CIMH), Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
| | - Stella Guldner
- Department of Child and Adolescent Psychiatry and Psychotherapy, Central Institute of Mental Health (CIMH), Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
- Institute of Cognitive and Clinical Neuroscience, Central Institute of Mental Health (CIMH), Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
| | - Maren Prignitz
- Institute of Cognitive and Clinical Neuroscience, Central Institute of Mental Health (CIMH), Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
| | - Frauke Nees
- Department of Child and Adolescent Psychiatry and Psychotherapy, Central Institute of Mental Health (CIMH), Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
- Institute of Cognitive and Clinical Neuroscience, Central Institute of Mental Health (CIMH), Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
- Institute of Medical Psychology and Medical Sociology, University Medical Center Schleswig Holstein, Kiel University, Kiel, Germany
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3
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Ernsten L, Körner LM, Schaper ML, Lawrenz J, Richards G, Heil M, Schaal NK. The association of prenatal amniotic sex hormones and digit ratio (2D:4D) in children aged 5 to 70 months: A longitudinal study. PLoS One 2023; 18:e0282253. [PMID: 36952430 PMCID: PMC10035896 DOI: 10.1371/journal.pone.0282253] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Accepted: 02/07/2023] [Indexed: 03/25/2023] Open
Abstract
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.
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Affiliation(s)
- Luisa Ernsten
- Department of Experimental Psychology, Heinrich-Heine-University, Düsseldorf, Germany
| | - Lisa M Körner
- Department of Experimental Psychology, Heinrich-Heine-University, Düsseldorf, Germany
- Department of General Pediatrics, Neonatology and Pediatric Cardiology, University Children's Hospital, Medical Faculty, Heinrich-Heine-University, Düsseldorf, Germany
| | - Marie Luisa Schaper
- Department of Experimental Psychology, Heinrich-Heine-University, Düsseldorf, Germany
| | - Judith Lawrenz
- Department of Experimental Psychology, Heinrich-Heine-University, Düsseldorf, Germany
| | - Gareth Richards
- School of Psychology, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Martin Heil
- Department of Experimental Psychology, Heinrich-Heine-University, Düsseldorf, Germany
| | - Nora K Schaal
- Department of Experimental Psychology, Heinrich-Heine-University, Düsseldorf, Germany
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4
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Digit ratio (2D:4D) and maternal testosterone-to-estradiol ratio measured in early pregnancy. Sci Rep 2022; 12:13586. [PMID: 35945232 PMCID: PMC9363442 DOI: 10.1038/s41598-022-17247-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2022] [Accepted: 07/22/2022] [Indexed: 11/09/2022] Open
Abstract
The ratio of index to ring finger (2D:4D) has been hypothesised to indicate prenatal androgen exposure, yet evidence for its validity is lacking. We report the first pre-registered study to investigate mothers' early pregnancy sex hormone concentrations in relation to their children's digit ratios measured at 18-22-month follow-up. Although the testosterone (T) to estradiol (E) ratio correlated negatively with right hand digit ratio (R2D:4D) and directional asymmetry (right-minus-left) in digit ratio (D[R-L]), neither effect remained statistically significant once demographic and obstetric covariates were controlled for. Nevertheless, the multivariate level of analysis did reveal that T correlated positively with left hand digit ratio (L2D:4D) and negatively with D[R-L]. However, the first of these effects is in the opposite direction to that predicted by theory. Taken together, the results of our study suggest research with larger samples is required to determine whether digit ratios are valid proxies for maternal sex hormone exposure.
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Lidborg LH, Cross CP, Boothroyd LG. A meta-analysis of the association between male dimorphism and fitness outcomes in humans. eLife 2022; 11:e65031. [PMID: 35179485 PMCID: PMC9106334 DOI: 10.7554/elife.65031] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2020] [Accepted: 02/17/2022] [Indexed: 11/13/2022] Open
Abstract
Humans are sexually dimorphic: men and women differ in body build and composition, craniofacial structure, and voice pitch, likely mediated in part by developmental testosterone. Sexual selection hypotheses posit that, ancestrally, more 'masculine' men may have acquired more mates and/or sired more viable offspring. Thus far, however, evidence for either association is unclear. Here, we meta-analyze the relationships between six masculine traits and mating/reproductive outcomes (96 studies, 474 effects, N = 177,044). Voice pitch, height, and testosterone all predicted mating; however, strength/muscularity was the strongest and only consistent predictor of both mating and reproduction. Facial masculinity and digit ratios did not significantly predict either. There was no clear evidence for any effects of masculinity on offspring viability. Our findings support arguments that strength/muscularity may be sexually selected in humans, but cast doubt regarding selection for other forms of masculinity and highlight the need to increase tests of evolutionary hypotheses outside of industrialized populations.
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Affiliation(s)
- Linda H Lidborg
- Department of Psychology, Durham UniversityDurhamUnited Kingdom
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6
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Second to fourth (2D:4D) digit ratio and their relationships among a mother and child population in Ghana. Sci Rep 2021; 11:13028. [PMID: 34158576 PMCID: PMC8219683 DOI: 10.1038/s41598-021-92358-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2021] [Accepted: 06/07/2021] [Indexed: 11/12/2022] Open
Abstract
The study aimed to determine the relationship between digit ratios among a mother–child population in Ghana. This was a cross-sectional study from December 2020 to April 2021 involving 272 mothers, their daughters (n = 132) and their sons (n = 140). The right (2D:4DR) and the left (2D:4DL) digit ratios were measured using computer-assisted analysis. The data were analysed in SPSS (v23) and GraphPad Prism (v8) at an alpha value of 0.05. The mean ± SD age of the mothers was 23.9 ± 3.67 years while the median (IQR) age of daughters was 116(54–240) days and sons, 134(54–240) days. The mean ± SD 2D:4DR were 0.94 ± 0.04, 0.91 ± 0.04 and 0.90 ± 0.04 respectively for mothers, daughters and sons. The mean ± SD 2D:4DL was 0.93 ± 0.04, for mothers, 0.92 ± 0.05 for daughters and 0.92 ± 0.05 for sons. The daughters and sons showed leftward asymmetry while the mothers showed rightward asymmetry in digit ratios. The 2D:4DR of sons was significantly lower than daughters (P = 0.031). There were negative correlations between the 2D:4DL and age of daughters (r = −0.182, P = 0.043) and sons (r = −0.221, P = 0.012). The 2D:4DR of mothers was positively correlated with that of daughters (r = 0.332, P = 0.000) and that of sons (r = 0.233, P = 0.008). There are significant relationships between digit ratios in a mother–child population.
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7
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Investigating the reliability and sex differences of digit lengths, ratios, and hand measures in infants. Sci Rep 2021; 11:10998. [PMID: 34040007 PMCID: PMC8155043 DOI: 10.1038/s41598-021-89590-w] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2021] [Accepted: 04/23/2021] [Indexed: 11/08/2022] Open
Abstract
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 (Dr-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.
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8
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Pubertal Testosterone and Brain Response to Faces in Young Adulthood: An Interplay between Organizational and Activational Effects in Young Men. J Neurosci 2021; 41:2990-2999. [PMID: 33589514 DOI: 10.1523/jneurosci.0190-20.2021] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2020] [Revised: 01/18/2021] [Accepted: 01/25/2021] [Indexed: 11/21/2022] Open
Abstract
According to the organizational-activational hypothesis, the organizational effects of testosterone during (prenatal) brain development moderate the activational effects of adult testosterone on behavior. Accumulating evidence supports the notion that adolescence is another period during which sex hormones organize the nervous system. Here we investigate how pubertal sex hormones moderate the activational effects of adult sex hormones on social cognition in humans. To do so, we recruited a sample of young men (n = 507; age, ∼19 years) from a longitudinal birth cohort and investigated whether testosterone exposure during adolescence (from 9 to 17 years of age) moderates the relation between current testosterone and brain response to faces in young adulthood, as assessed with functional magnetic resonance imaging (fMRI). Our results showed that the cumulative exposure to testosterone during adolescence moderated the relation between adult testosterone and both the mean fMRI response and functional connectivity (i.e., node strength). Specifically, in participants with low exposure to testosterone during puberty, we observed a positive relationship between current testosterone and the brain response to faces; this was not the case for participants with medium and high pubertal testosterone. Furthermore, we observed a stronger relationship between the brain response and current testosterone in parts of the angry-face network associated with (vs without) motion in the eye region of an observed (angry) face. We speculate that pubertal testosterone modulates the relationship between current testosterone and brain response to social cues carried by the eyes and signaling a potential threat.SIGNIFICANCE STATEMENT Accumulating evidence supports the organizational effects of pubertal testosterone, but the body of literature examining these effects on social cognition in humans is in its infancy. With a sample of young men from a longitudinal birth cohort, we showed that the cumulative exposure to testosterone during adolescence moderated the relation between adult testosterone and both the mean BOLD signal change and functional connectivity. Specifically, we observed a positive relationship between adult testosterone and the brain response to faces in participants with low exposure to testosterone during puberty, but not in participants with medium and high pubertal testosterone. Results of further analysis suggest that sensitivity to cues carried by the eyes might underlie the relationship between testosterone and brain response to faces, especially in the context of a potential threat.
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Richards G, Medland SE, Beaton AA. Digit ratio (2D:4D) and handedness: A meta-analysis of the available literature. Laterality 2021; 26:421-484. [PMID: 33517845 DOI: 10.1080/1357650x.2020.1862141] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The Geschwind-Behan-Galaburda and sexual differentiation models predict an association between elevated foetal androgen exposure and left-handedness whereas the callosal hypothesis predicts the opposite. We present a meta-analysis of correlations between handedness and digit ratio (2D:4D), a putative marker of prenatal testosterone. Left-handedness predicted low (male-typical) right-hand digit ratio (R2D:4D), high (female-typical) left-hand digit ratio (L2D:4D), and low R2D:4D-L2D:4D directional asymmetry (D[R-L]). Effect sizes were extremely small and not moderated by sex or method of measuring handedness or 2D:4D. The same general pattern was observed after excluding the very large study (110,329 males, 90,412 females) of Manning and Peters ([2009]. Digit ratio (2D:4D) and hand preference for writing in the BBC Internet Study. Laterality: Asymmetries of Body, Brain and Cognition, 14(5), 528-540. doi:10.1080/13576500802637872); however, no significant effects for R2D:4D were observed once these samples were removed. The results do not confirm any theory linking prenatal androgens with handedness, so we speculate they instead reflect the mechanical action of writing causing subtle changes in the musculature and/or fat pads of the fingers. Gripping a pen/pencil might cause an increase in 2D relative to 4D (and/or decrease in 4D relative to 2D) resulting in higher ratios on the writing-hand; furthermore, this could differ between left- and right-handers due to writing in the left-to-right direction (as in English) having asymmetrical effects depending on which hand is used.
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Affiliation(s)
- Gareth Richards
- School of Psychology, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, UK.,Autism Research Centre, Department of Psychiatry, University of Cambridge, Cambridge, UK.,Centre for Research on Play in Education, Development & Learning, Faculty of Education, University of Cambridge, Cambridge, UK
| | - Sarah E Medland
- Psychiatric Genetics, QIMR Berghofer Medical Research Institute, Brisbane, Australia.,School of Psychology, University of Queensland, St Lucia, Australia.,School of Psychology and Counselling, Queensland University of Technology, Brisbane, Australia
| | - Alan A Beaton
- Department of Psychology, School of Human & Health Sciences, Swansea University, Swansea, UK.,Department of Psychology, Aberystwyth University, Aberystwyth, UK
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Digit ratio (2D:4D) and amniotic testosterone and estradiol: an attempted replication of Lutchmaya et al. (2004). J Dev Orig Health Dis 2021; 12:859-864. [PMID: 33472723 DOI: 10.1017/s2040174420001294] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The ratio of length between the second (index) and fourth (ring) fingers (digit ratio or 2D:4D) is frequently employed as a retrospective marker of prenatal sex hormone exposure. Lutchmaya et al. (2004) reported that the ratio of testosterone (T) to estradiol (E) present in second-trimester amniotic fluid was negatively correlated with digit ratios for the right hand (but not the left hand) in a sample of 29 children at 2-year follow-up. This observation is frequently cited as evidence for the measure's validity but has not been replicated. We therefore present the findings of another study of amniotic T and E that did not find evidence for these effects at 4½-year follow-up. The confidence intervals were large, the direction of correlations observed was generally erratic, and the overall findings question the premise that second-trimester sex hormones affect the development of digit length ratios in humans.
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11
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A Pre-registered Meta-analysis Based on Three Empirical Studies Reveals No Association Between Prenatal (Amniotic) Cortisol Exposure and Fluctuating Asymmetry in Human Infants. Evol Biol 2021. [DOI: 10.1007/s11692-020-09523-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
AbstractDevelopmental instability (DI) reflects an organism’s inability to develop an ideal phenotype when challenged by genetic and environmental insults. DI can be estimated via the proxy measure of fluctuating asymmetry (FA), i.e., the small random deviations from perfect bilateral symmetry observed in the morphology of paired traits. The mechanisms involved in the genesis of FA in human populations are relatively unknown, though animal research indicates that hormonal processes may be involved. As maternal stress during pregnancy is detrimental to various developmental processes, elevated prenatal cortisol may represent a causal factor in the subsequent emergence of an asymmetrical phenotype. The main purpose of this pre-registered meta-analysis based on three empirical studies was to investigate whether mid-trimester amniotic cortisol levels predict subsequent FA in finger lengths of infants from Germany, Portugal, and the UK. No statistically significant relationships were observed, and meta-analytic combination of the effect size estimates yielded a null result. We did, however, detect significant positive correlations between the cortisol present in the amniotic fluid and maternal plasma in the Portuguese cohort, and observed that FA in the German cohort was significantly lower at 70-months than at either 9- or 20-months. Taken together, the current findings run contrary to animal research showing that elevated prenatal corticosterone exposure leads to increased FA. However, this may be because a single cortisol assay obtained via amniocentesis is an inadequate proxy for average gestational exposure, and/or that prenatal cortisol levels at an earlier (i.e., first rather than second trimester) stage of pregnancy is what explains variance in subsequent FA.
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12
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Androgens and offending behavior: Evidence based on multiple self-reported measures of prenatal and general testosterone exposure. PERSONALITY AND INDIVIDUAL DIFFERENCES 2021. [DOI: 10.1016/j.paid.2020.110282] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Jones AL, Jaeger B, Schild C. No credible evidence for links between 2D:4D and COVID-19 outcomes: A probabilistic perspective on digit ratio, ACE variants, and national case fatalities. Early Hum Dev 2021; 152:105272. [PMID: 33227636 PMCID: PMC7670914 DOI: 10.1016/j.earlhumdev.2020.105272] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/23/2020] [Revised: 11/04/2020] [Accepted: 11/10/2020] [Indexed: 10/26/2022]
Abstract
Research into COVID-19 susceptibility and outcomes are critical, but claims must be carefully evaluated to inform policy decisions. In a recent series of articles, Manning and Fink [1-3] use national-level data to describe associations between case-fatality ratios and male and female finger ratios (2D:4D), a suggested measure of prenatal androgen exposure, as well as angiotensin-converting enzyme (ACE) allele and genotype frequencies. The authors suggest that 2D:4D is linked with ACE variant prevalence, and that higher male 2D:4D is associated with higher case fatality ratios, and point to 2D:4D as a useful prognostic measure for COVID-19 susceptibility. A critical review and robust Bayesian analysis of the hypothesis is described here, finding no conclusive evidence of COVID-19 mortality and 2D:4D, nor associations between 2D:4D and ACE1 allele or ACE2 genotype frequency. This absence of evidence is present for data taken from the second wave of COVID-19 in October 2020. Problematic theoretical grounding, individual-level conclusions drawn from national-level data, and issues with statistical inference in the original articles are discussed. Taken together, the current data offer no clear utility of 2D:4D in determining COVID-19 outcomes.
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Affiliation(s)
- Alex L. Jones
- Swansea University, United Kingdom,Corresponding author
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14
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Digit ratio, a proposed marker of the prenatal hormone environment, is not associated with prenatal sex steroids, anogenital distance, or gender-typed play behavior in preschool age children. J Dev Orig Health Dis 2020; 12:923-932. [PMID: 33336644 DOI: 10.1017/s2040174420001270] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Prenatal hormones have been proposed as key factors impacting child development as well as long-term health and disease. Digit ratio (the ratio of the lengths of the second to fourth digits; 2D:4D) has been proposed as a sexually dimorphic, noninvasive marker of prenatal androgen exposure that can be reliably measured in children and adults. To date, few longitudinal pregnancy cohort studies have examined childhood digit ratio in relation to other relevant measures including prenatal hormones and androgen-sensitive outcomes. To augment the current literature on this topic, we measured right-hand digit ratio in 4-year-old children participating in The Infant Development and the Environment Study, a multicenter longitudinal cohort study that has been following mother-child dyads since the first trimester of pregnancy (n = 321). We assessed sex differences in digit ratio and fit multivariable linear regression models to examine digit ratio in relation to: (1) child sex; (2) maternal sex steroid hormone concentrations in early pregnancy; (3) newborn anogenital distance, another proposed measure of sensitivity to prenatal androgens; and (4) gender-typical play behavior as measured by the Preschool Activities Inventory (PSAI) at age 4. We observed no sex difference in digit ratio; the mean 2D:4D was 0.97 ± 0.05 mm in both sexes. Furthermore, digit ratio was not associated with maternal sex steroid concentrations in early pregnancy, anogenital distance in either sex, or PSAI scores in either sex in covariate-adjusted models. In conclusion, we observed no evidence that early childhood digit ratio was associated with child sex or hormone-sensitive measures in this cohort.
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Nowak-Kornicka J, Borkowska B, Pawłowski B. Masculinity and immune system efficacy in men. PLoS One 2020; 15:e0243777. [PMID: 33315964 PMCID: PMC7735617 DOI: 10.1371/journal.pone.0243777] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2020] [Accepted: 11/25/2020] [Indexed: 01/23/2023] Open
Abstract
Masculinity-related morphological traits are supposed to be honest indicators of a man's biological quality. While some studies showed that sexually dimorphic traits are related to various aspects of biological condition such as general health, immunity or fertility, still little is known about the relationship between masculine traits and the effectiveness of innate and adaptive immunity in humans. The aim of this study was to see if masculine traits, which are dependent on androgen levels in foetal and pubertal stages of development, are related to the immune quality in healthy men. The immune quality was evaluated for 91 healthy men aged 19-36 years. Immunity measurements included innate and adaptive parameters. General health status, age, testosterone level, BMI, physical activity, and smoking were controlled. The shoulder-to-hip ratio (SHR), 2D:4D digit ratio and hand-grip strength (HGS) were used as markers of masculinization. The regressions showed that when controlling for confounds, masculinity-related traits were in general not related to innate and adaptive immunity. Only a weak association was observed for right 2D:4D ratio and T-lymphocyte counts (but it becomes non-significant after adjustment for multiple comparisons). Our results do not support the premise that masculinity is a cue for immunological quality in men. However, the positive association between right 2D:4D and T lymphocytes might suggest that further studies are needed to verify if androgen stimulation in prenatal development might be related to immunity in adulthood.
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16
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Effects of hand preference on digit lengths and digit ratios among children and adults. Early Hum Dev 2020; 151:105204. [PMID: 33059164 DOI: 10.1016/j.earlhumdev.2020.105204] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/02/2020] [Revised: 09/28/2020] [Accepted: 09/29/2020] [Indexed: 01/21/2023]
Abstract
BACKGROUND Prenatal sex hormones may not exclusively determine effects of hand preference on digit ratios. Genetic determination is an alternative possibility. AIM To study the likelihood of similar effects of hand preference on digit lengths and digit ratios. METHODS We selected similar numbers of left-handers and right-handers in samples of kindergarten children (N = 101, age range: 3.5-7 years) and adults (N = 189, age range: 17-28 years) and measured digit lengths (excluding the thumb) directly on the palmar hand. RESULTS Compared to right-handers, left-handers had longer digits and lower third-to-fourth (3D:4D) digit ratios among children, whereas an opposite pattern of handedness differences occurred among adults. CONCLUSIONS Effects of hand preference on digit lengths and ratios might be genetically/ontogenetically determined. Also discussed are implications of this set of findings for digit ratio research.
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Richards G, Baron-Cohen S, van Steen T, Galvin J. Assortative mating and digit ratio (2D:4D): A pre-registered empirical study and meta-analysis. Early Hum Dev 2020; 151:105159. [PMID: 32942249 DOI: 10.1016/j.earlhumdev.2020.105159] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Revised: 08/10/2020] [Accepted: 08/18/2020] [Indexed: 02/06/2023]
Abstract
BACKGROUND It has been hypothesised that the ratio of length between the second and fourth fingers (2D:4D), commonly employed as an indicator of foetal sex hormone exposure, may be positively correlated between heterosexual partners. AIMS As previous evidence has been conflicting, our study aimed to determine whether intra-couple correlations exist for digit ratio variables, and if so, to estimate the size and direction of these effects. STUDY DESIGN We present a preregistered (osf.io/6jg8p) correlational study and quantitative meta-analysis of the available literature, and attempted to locate further published and unpublished data (i.e. 'grey literature') by contacting n = 248 researchers in the 2D:4D and related fields. SUBJECTS n = 58 heterosexual dating couples from the UK took part in our empirical study, and the meta-analysis included data from k = 11 samples. OUTCOME MEASURES We measured digit ratio for the right hand (R2D:4D), left hand (L2D:4D), and average of both hands (M2D:4D), as well as the right-left-difference (D[R-L]). RESULTS We found no evidence of significant positive intra-couple correlations in our own data, but a significant (positive) meta-analytic effect size estimate emerged for R2D:4D (r = 0.072, p = 0.014). The meta-analytic effects for L2D:4D (r = 0.043, p = 0.303), M2D:4D (r = 0.070, p = 0.225), and D[R-L] (r = 0.028, p = 0.649) were all in the same direction but not statistically significant. However, if the sample from Klimek et al. (2014, 2016) were omitted, meta-analysis would also yield a significant positive correlation for M2D:4D (r = 0.128, p = 0.001). CONCLUSIONS Although our findings are based on a fairly small range of studies, which themselves provide a relatively small sample of participants, they do imply the intriguing possibility of small effects of positive assortment in relation to characteristics associated with the prenatal hormonal environment.
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Affiliation(s)
- Gareth Richards
- School of Psychology, Faculty of Medical Sciences, Newcastle University, UK; Autism Research Centre, Department of Psychiatry, University of Cambridge, UK.
| | - Simon Baron-Cohen
- Autism Research Centre, Department of Psychiatry, University of Cambridge, UK
| | - Tommy van Steen
- Institute of Security and Global Affairs, Universiteit Leiden, Netherlands
| | - John Galvin
- Department of Psychology, Birmingham City University, UK
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18
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Richards G, Browne WV, Aydin E, Constantinescu M, Nave G, Kim MS, Watson SJ. Digit ratio (2D:4D) and congenital adrenal hyperplasia (CAH): Systematic literature review and meta-analysis. Horm Behav 2020; 126:104867. [PMID: 32998030 DOI: 10.1016/j.yhbeh.2020.104867] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/07/2020] [Revised: 09/18/2020] [Accepted: 09/19/2020] [Indexed: 01/15/2023]
Abstract
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.
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Affiliation(s)
- Gareth Richards
- School of Psychology, Faculty of Medical Sciences, Newcastle University, UK; Autism Research Centre, Department of Psychiatry, University of Cambridge, UK.
| | | | - Ezra Aydin
- Autism Research Centre, Department of Psychiatry, University of Cambridge, UK
| | - Mihaela Constantinescu
- Gender Development Research Centre, University of Cambridge, UK; School of Psychology, University of East London, UK
| | - Gideon Nave
- Marketing Department, The Wharton School, University of Pennsylvania, USA
| | - Mimi S Kim
- Keck School of Medicine, University of Southern California, USA
| | - Steven J Watson
- School of Psychology, Faculty of Medical Sciences, Newcastle University, UK; Department of Psychology of Conflict, Risk and Safety, University of Twente, Netherlands
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19
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Baxter A, Wood EK, Witczak LR, Bales KL, Higley JD. Sexual Dimorphism in Titi Monkeys' Digit (2D:4D) Ratio is Associated with Maternal Urinary Sex Hormones During Pregnancy. Dev Psychobiol 2020; 62:979-991. [PMID: 31372988 PMCID: PMC7871332 DOI: 10.1002/dev.21899] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2019] [Revised: 06/15/2019] [Accepted: 06/28/2019] [Indexed: 12/23/2022]
Abstract
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.
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Affiliation(s)
- Alexander Baxter
- Department of Psychology, Brigham Young University, Provo, Utah
- Department of Psychology, University of California, Davis, California
- California National Primate Research Center, Davis, California
| | | | - Lynea R Witczak
- Department of Psychology, University of California, Davis, California
- California National Primate Research Center, Davis, California
| | - Karen L Bales
- Department of Psychology, University of California, Davis, California
- California National Primate Research Center, Davis, California
| | - J Dee Higley
- Department of Psychology, Brigham Young University, Provo, Utah
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20
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Kowal M, Sorokowski P, Żelaźniewicz A, Nowak J, Orzechowski S, Żurek G, Żurek A, Juszkiewicz A, Wojtycka L, Sieniuć W, Poniatowska M, Tarnowska K, Kowalska K, Drabik K, Łukaszek P, Krawczyk K, Stefaniak T, Danek N. No relationship between the digit ratios (2D:4D) and salivary testosterone change: Study on men under an acute exercise. Sci Rep 2020; 10:10068. [PMID: 32572079 PMCID: PMC7308391 DOI: 10.1038/s41598-020-66915-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2019] [Accepted: 03/16/2020] [Indexed: 01/08/2023] Open
Abstract
The digit ratio (2D:4D) is said to be a potential marker of exposure to prenatal sex steroids. Some studies suggest that the 2D:4D is also linked with the testosterone response to challenging situations due to organizational effect of prenatal hormonal milieu on adult endocrine functioning. However, up to date, there were only four studies (conducted on small samples) that examined the 2D:4D and the testosterone response to a challenging situation (i.e. physical exertion or aggressive context). Here, we examined the relationship between the 2D:4D and the testosterone change under an acute exercise among 97 men. We found that the digit ratios (the right 2D:4D, the left 2D:4D, and the right minus left 2D:4D) were neither predictors of pre-exercise testosterone, nor the change in testosterone level after a cycling task. Our results add a contradictory to previous studies evidence in a discussion on the links of the 2D:4D and the testosterone change.
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Affiliation(s)
- Marta Kowal
- Institute of Psychology, University of Wrocław, Wrocław, Poland
| | - Piotr Sorokowski
- Institute of Psychology, University of Wrocław, Wrocław, Poland.
| | | | - Judyta Nowak
- Department of Human Biology, University of Wrocław, Wrocław, Poland
| | | | - Grzegorz Żurek
- University School of Physical Education in Wrocław, Wrocław, Poland
| | - Alina Żurek
- Institute of Psychology, University of Wrocław, Wrocław, Poland
| | | | - Lidia Wojtycka
- Institute of Psychology, University of Wrocław, Wrocław, Poland
| | | | | | | | - Kaja Kowalska
- Institute of Psychology, University of Wrocław, Wrocław, Poland
| | | | | | | | | | - Natalia Danek
- University School of Physical Education in Wrocław, Wrocław, Poland
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21
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Gazioglu S, Alkan I, Karaman AG, Boz C. Decreased second to fourth digit ratios in female multiple sclerosis patients. Early Hum Dev 2020; 144:105039. [PMID: 32304983 DOI: 10.1016/j.earlhumdev.2020.105039] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Revised: 03/27/2020] [Accepted: 03/31/2020] [Indexed: 01/10/2023]
Abstract
BACKGROUND Sex-related differences in multiple sclerosis (MS) suggest a possible role of prenatal sex hormones in the pathogenesis. The aim of this study was to investigate whether the 2D:4D ratio, considered a predictor of prenatal hormonal exposure, in MS patients differ from that in healthy controls. METHODS Two hundred MS patients and one hundred seventy healthy control subjects with similar age and sex distribution enrolled. All participants were right-handed. The right hands of all participants were scanned using a digital scanner. Measurements of second and fourth digit lengths were made from digital scans. The 2D:4D ratio was calculated by dividing the length of the second digit by the length of the fourth digit. RESULTS A total of 171 MS patients' and 159 healthy controls' digit scans included in the study. The MS group consisted of 94 females (mean age 38.32 ± 10.5) and 77 males (mean age 42.06 ± 11.8) and the control group of 86 females (mean age 40.24 ± 9.7) and 73 males (mean age 38.49 ± 11.6). 2D:4D ratios of female MS patients were significantly lower than those of healthy females (p=0.004). Although 2D:4D ratios of male patients with MS were lower than those of healthy males, this difference was not statistically significant (p=0.33). There was no significant correlation between the 2D:4D ratio, EDSS levels or duration of the disease in male or female MS patients (p<0.05). CONCLUSION Although our results suggest that a prenatal hormonal balance in favor of androgenic activity may be a risk factor for MS, complex factors mediating the actions of sex hormones on target cells should always be considered when evaluating the effects of sex hormones.
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Affiliation(s)
- Sibel Gazioglu
- Department of Neurology, Karadeniz Technical University Medical Faculty, 61080 Trabzon, Turkey.
| | - Ismail Alkan
- Department of Neurology, Karadeniz Technical University Medical Faculty, 61080 Trabzon, Turkey
| | - Ayse Gul Karaman
- Department of Neurology, Karadeniz Technical University Medical Faculty, 61080 Trabzon, Turkey
| | - Cavit Boz
- Department of Neurology, Karadeniz Technical University Medical Faculty, 61080 Trabzon, Turkey
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22
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Nitschke JP, Bartz JA. Lower digit ratio and higher endogenous testosterone are associated with lower empathic accuracy. Horm Behav 2020; 119:104648. [PMID: 31785282 DOI: 10.1016/j.yhbeh.2019.104648] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/25/2019] [Revised: 11/22/2019] [Accepted: 11/23/2019] [Indexed: 01/10/2023]
Abstract
Empathy is a cornerstone of human sociality. It has important consequences for our interpersonal relationships and for navigating our social world more generally. Although research has identified numerous psychological factors that can influence empathy, evidence suggests that empathy may also be rooted in our biology and, in particular, the gonadal steroid hormone testosterone. To date, much of the research linking testosterone and empathy has focused on the 2D:4D ratio (i.e., the ratio of the lengths of the index and ring fingers), and the results have been mixed. These mixed results, however, may be due to reliance on self-report measures to assess empathy, which can be vulnerable to self-presentation, as well as social-cultural norms about gender/sex differences in empathy. Moreover, although some have argued that digit ratio is an indicator of prenatal androgen exposure, the evidence for this to date is weak. Here, we aimed to follow up on this prior work, using a naturalistic empathic accuracy task in which participants dynamically track, in real-time, the emotional state of targets. We show that lower digit ratio (Study 1; N = 107) and higher circulating testosterone (Study 2; N = 76) are associated with poorer empathic accuracy performance; critically, these effects hold when controlling for sex/gender. In neither study, however, did we find effects on self-reported empathy. Our results highlight the limitations of self-report measures and support the notion that endogenous testosterone levels as well as 2D:4D ratio are related to key social-cognitive competencies like empathic accuracy.
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23
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O'Kelly F, DeCotiis K, Zu'bi F, Farhat WA, Koyle MA. Increased hand digit length ratio (2D:4D) is associated with increased severity of hypospadias in pre-pubertal boys. Pediatr Surg Int 2020; 36:247-253. [PMID: 31748946 DOI: 10.1007/s00383-019-04600-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 11/07/2019] [Indexed: 12/28/2022]
Abstract
INTRODUCTION Hypospadias is a common congenital male disorder, with much research focusing on prenatal androgen exposure as a causative factor. Whilst digit length ratios were apparent in sexual dimorphism since the nineteenth century, their role in hypospadias remains unknown. The objective of our study was to determine the correlation between digit length (2D:4D) ratio, hypospadias severity, and anogenital distance. METHODS Pre-pubertal boys (<3 years old) seen intra/postoperatively following hypospadias repair (June 2018-January 2019 inc.) were included. These were age-matched to non-hypospadias controls. Anthropomorphic measurements of digit lengths, penile/glans width, and anogenital distance were measured using digital calipers. RESULTS Data measurements were collected for 105 boys with hypospadias (60 distal; 45 proximal) and 55 controls. There were significant differences in 2D:4D ratios in each hand (p < 0.001), as well as individual digits (p < 0.001), and a reduced anogenital distance (p < 0.001), when comparing the proximal group with distal or control groups. There were no significant differences in glans width, or between term- and preterm births. CONCLUSIONS This study is the first to demonstrate increased 2D:4D ratios with proximal hypospadias, which also correlate with a shortened anogenital distance. This may provide a non-invasive, potentially antenatal, anthropomorphic measurement, as an indirect indicator of aberrant urogenital development.
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Affiliation(s)
- Fardod O'Kelly
- Division of Urology, The Hospital for Sick Children, Toronto, ON, M5G1X8, Canada.
| | - Keara DeCotiis
- Division of Urology, The Hospital for Sick Children, Toronto, ON, M5G1X8, Canada
| | - Fadi Zu'bi
- Division of Urology, The Hospital for Sick Children, Toronto, ON, M5G1X8, Canada
| | - Walid A Farhat
- Division of Urology, The Hospital for Sick Children, Toronto, ON, M5G1X8, Canada
| | - Martin A Koyle
- Division of Urology, The Hospital for Sick Children, Toronto, ON, M5G1X8, Canada
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Brañas-Garza P, Espín AM, García-Muñoz T, Kovářík J. Digit ratio (2D : 4D) and prosocial behaviour in economic games: no direct correlation with generosity, bargaining or trust-related behaviours. Biol Lett 2019; 15:20190185. [PMID: 31455172 PMCID: PMC6731481 DOI: 10.1098/rsbl.2019.0185] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2019] [Accepted: 07/26/2019] [Indexed: 12/12/2022] Open
Abstract
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.
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Affiliation(s)
- Pablo Brañas-Garza
- Department of Economics, LoyolaBehLAB, Universidad Loyola Andalucía, Cordoba, Andalucia 14004, Spain
| | - Antonio M. Espín
- Department of Social Anthropology, Universidad de Granada, Granada, Granada 18071, Spain
| | - Teresa García-Muñoz
- Department of Quantitative Methods, Universidad de Granada, Granada 18071, Spain
| | - Jaromír Kovářík
- Department of Economics, Universidad del País Vasco (UPV/EHU), Bilbao, País Vasco, Spain
- CERGE-EI, Prague, Czech Republic
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