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Eckstein F, Putz R, Wirth W. Sexual dimorphism in peri-articular tissue anatomy - More keys to understanding sex-differences in osteoarthritis? OSTEOARTHRITIS AND CARTILAGE OPEN 2024; 6:100485. [PMID: 38946793 PMCID: PMC11214405 DOI: 10.1016/j.ocarto.2024.100485] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2024] [Accepted: 05/07/2024] [Indexed: 07/02/2024] Open
Abstract
Objective Osteoarthritis prevalence differs between women and men; whether this is the result of differences in pre-morbid articular or peri-articular anatomical morphotypes remains enigmatic. Albeit sex within humans cannot be reduced to female/male, this review focusses to the sexual dimorphism of peri-articular tissues, given lack of literature on non-binary subjects. Methods Based on a Pubmed search and input from experts, we selected relevant articles based on the authors' judgement of relevance, interest, and quality; no "hard" bibliometric measures were used to evaluate the quality or importance of the work. Emphasis was on clinical studies, with most (imaging) data being available for the knee and thigh. Results The literature on sexual dimorphism of peri-articular tissues is reviewed: 1) bone size/shape, 2) subchondral/subarticular bone, 3) synovial membrane and infra-patellar fad-pad (IPFP), 4) muscle/adipose tissue, and 5) peri-articular tissue response to treatment. Conclusions Relevant sex-specific differences exist for 3D bone shape and IPFP size, even after normalization to body weight. Presence of effusion- and Hoffa-synovitis is associated with greater risk of incident knee osteoarthritis in overweight women, but not in men. When normalized to bone size, men exhibit greater muscle, and women greater adipose tissue measures relative to the opposite sex. Reduced thigh muscle specific strength is associated with incident knee osteoarthritis and knee replacement in women, but not in men. These observations may explain why women with muscle strength deficits have a poorer prognosis than men with similar deficits. A "one size/sex fits all" approach must be urgently abandoned in osteoarthritis research.
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Affiliation(s)
- Felix Eckstein
- Research Program for Musculoskeletal Imaging, Center for Anatomy and Cell Biology, Paracelsus Medical University, Salzburg, Austria
- Ludwig Boltzmann Institute for Arthritis and Rehabilitation (LBIAR), Paracelsus Medical University, Salzburg, Austria
- Chondrometrics GmbH, Ainring, Germany
| | - Reinhard Putz
- Anatomische Anstalt, Ludwig Maximilians Universität München, Munich, Germany
| | - Wolfgang Wirth
- Research Program for Musculoskeletal Imaging, Center for Anatomy and Cell Biology, Paracelsus Medical University, Salzburg, Austria
- Ludwig Boltzmann Institute for Arthritis and Rehabilitation (LBIAR), Paracelsus Medical University, Salzburg, Austria
- Chondrometrics GmbH, Ainring, Germany
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Kasielska-Trojan A, Manning JT, Kałuża M, Głowacka E, Antoszewski B. First trimester maternal sex steroids and the digit ratios of mothers and children. Early Hum Dev 2024; 195:106067. [PMID: 38889565 DOI: 10.1016/j.earlhumdev.2024.106067] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/11/2024] [Revised: 06/12/2024] [Accepted: 06/14/2024] [Indexed: 06/20/2024]
Abstract
BACKGROUND It is thought that digit ratios (2D:4D) are a correlate of 1st trimester maternal and foetal sex steroids. Here we consider the relationship of 2D:4D to the former. METHOD Digit lengths were directly measured with a calliper at infant age 13 months. Measures of T and E were obtained from mother's blood at 6-8 weeks, 10-11 weeks and 1st trimester means were calculated. RESULTS There were 69 mother-infant pairs (33 boys). Sex differences in 2D:4D (boysboys) were found. For mothers of girls: there were negative relationships between 2D:4D and T at 6-8 weeks, 10-11 weeks and 1st trimester means. For infants: girls showed more correlations between 2D:4D and hormones than boys. For boys, there was one positive association between 2D:4D and E and two positive associations for E/T. For girls, 2D:4D was negatively related to T (four correlations) and positively related to E/T (four correlations). Considering associations in the total sample and controlling for sex, at 6-8 weeks right and left 2D:4D were positively related to E. At 10-11 weeks, right and left 2D:4D were negatively related to T. For 1st trimester means, 2D:4D's were positively related to E (right and left) and negatively related to T (right). CONCLUSION Infant 2D:4D was correlated with first trimester maternal sex steroids, particularly at 10-11 weeks. The correlations were negative for T, and positive for E and E/T with weaker effects for male infants. The latter pattern may arise because in boys T produced by foetal testes masks the effect of maternal T.
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Affiliation(s)
- Anna Kasielska-Trojan
- Plastic, Reconstructive and Aesthetic Surgery Clinic, Institute of Surgery, Medical University of Lodz, Lodz, Poland.
| | - John T Manning
- School of Sport and Exercise Sciences, Applied Sports, Technology, Exercise, and Medicine (A-STEM), Swansea University, Swansea, UK.
| | - Marek Kałuża
- Out-patient Clinics, Polish Mother Research Institute, Lodz, Poland
| | - Ewa Głowacka
- Center of Medical Laboratory Diagnostics and Screening Tests, Polish Mother's Memorial Hospital-Research Institute, Lodz, Poland
| | - Bogusław Antoszewski
- Plastic, Reconstructive and Aesthetic Surgery Clinic, Institute of Surgery, Medical University of Lodz, Lodz, Poland
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Ribeiro E, Neave N, Marsili BK, Figueiredo ECG, Martino-Andrade AJ, de Moraes RN. Prenatal androgenization (2D:4D) predictions of tennis match-play success in junior players: A search for physiological explanations. Am J Hum Biol 2024; 36:e23979. [PMID: 37602536 DOI: 10.1002/ajhb.23979] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2023] [Revised: 08/01/2023] [Accepted: 08/04/2023] [Indexed: 08/22/2023] Open
Abstract
AIM This study aims to investigate the possible association between digit ratio (2D:4D) and match-play success (MPS) in junior tennis players. In addition, we consider the possible explanatory pathways of these associations in relation to psychological, strength, power, and hormonal parameters. METHODS We performed a cross-sectional study, with a sample comprised of 64 male junior tennis players (11-18 years old). Digit ratio was calculated from direct finger measurements. In addition, we measured the ratio of wins by number of matches played in 5 years of official competition (MPS), handgrip strength (HGS), standing long jump (SLJ), training (in weekly hours), and expertise (number of years in official competition). Salivary testosterone and cortisol levels were measured before and after physical "challenge" tests. RESULTS The 2D:4D correlated negatively with HGS and SLJ. MPS was also negatively associated with 2D:4D, but was positively correlated to HGS, expertise, training, and self-confidence (SC). Multiple linear regression showed 2D:4D and expertise were associated with MPS (43%-54%). None of the physical, or hormonal variables tested explained the links between 2D:4D and MPS. CONCLUSION Therefore, the specific fitness components influenced by prenatal androgenization that moderate sports success remain unknown. Future studies should explore the interaction of 2D:4D, with tennis exercises as a challenge to induce hormonal change, the effect of pubertal stage, and the influence of aerobic endurance in determining MPS.
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Affiliation(s)
- Evaldo Ribeiro
- Litoral Sector, Federal University of Paraná, Matinhos, Brazil
- Department of Physiology, Federal University of Paraná, Curitiba, Brazil
| | - Nick Neave
- Department of Psychology, Northumbria University, Newcastle-upon-Tyne, UK
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4
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Manning JT, Fink B, Trivers R. Digit Ratio (2D:4D; Right-Left 2D:4D) and Multiple Phenotypes for Same-Sex Attraction: The BBC Internet Study Revisited. ARCHIVES OF SEXUAL BEHAVIOR 2024; 53:213-222. [PMID: 37847344 PMCID: PMC10794480 DOI: 10.1007/s10508-023-02703-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2023] [Revised: 09/04/2023] [Accepted: 09/05/2023] [Indexed: 10/18/2023]
Abstract
Same-sex attraction may be linked to low prenatal androgen (in men) and high prenatal androgen (in women). Digit ratio (2D:4D) is thought to be a negative correlate of prenatal androgen and right-left 2D:4D (Dr-l) to reflect lateralized differences in sensitivity to prenatal androgen. Lower 2D:4D has been reported for lesbians compared to heterosexuals, but links to high 2D:4D in gay men are less clear. The largest study thus far (the BBC Internet study) found no significant difference between the 2D:4D of lesbians and heterosexual women but a higher 2D:4D in gay men compared to heterosexual men. Here we consider the possibility that low and high prenatal androgen is associated with same-sex attraction in men (n = 108,779) and women (n = 87,742), resulting in more than two phenotypes. We examined the associations between 2D:4D, Dr-l, and same-sex attraction scores in the BBC Internet study. In contrast to the earlier report, which considered sexual orientation in categories, there were positive linear associations in men (right and left 2D:4D, but not Dr-l) and negative linear associations in women (right 2D:4D and Dr-l, but not left 2D:4D). There were no curvilinear relationships for right and left 2D:4D. However, Dr-l showed a U-shaped association with same-sex attraction in men. Thus, (1) high prenatal androgen may be implicated in female homosexuality, while both low and high prenatal androgen may be implicated in male homosexuality, and (2) large side differences in sensitivity to androgen may be associated with elevated same-sex attraction in men.
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Affiliation(s)
- John T Manning
- Applied Sports, Technology, Exercise, and Medicine (A-STEM), Swansea University, Swansea, UK
| | - Bernhard Fink
- Biosocial Science Information, Biedermannsdorf, Austria.
- Department of Evolutionary Anthropology, University of Vienna, Djerassiplatz 1, 1030, Vienna, Austria.
- Human Evolution and Archaeological Sciences (HEAS), University of Vienna, Vienna, Austria.
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Burke FF, Hinks M, Salia S, Sparkes KM, Swift-Gallant A. Using Animal Models to Study the Interplay Between the Biodevelopmental Pathways Underlying Human Sexual Orientation. ARCHIVES OF SEXUAL BEHAVIOR 2023; 52:2979-2984. [PMID: 36477673 DOI: 10.1007/s10508-022-02499-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2022] [Revised: 11/22/2022] [Accepted: 11/23/2022] [Indexed: 06/17/2023]
Affiliation(s)
- Francine F Burke
- Department of Psychology, Memorial University of Newfoundland, 230 Elizabeth Ave., St John's, NL, A1B 3X9, Canada
| | - Meagan Hinks
- Department of Psychology, Memorial University of Newfoundland, 230 Elizabeth Ave., St John's, NL, A1B 3X9, Canada
| | - Stephanie Salia
- Department of Psychology, Memorial University of Newfoundland, 230 Elizabeth Ave., St John's, NL, A1B 3X9, Canada
| | - Kerri M Sparkes
- Department of Psychology, Memorial University of Newfoundland, 230 Elizabeth Ave., St John's, NL, A1B 3X9, Canada
| | - Ashlyn Swift-Gallant
- Department of Psychology, Memorial University of Newfoundland, 230 Elizabeth Ave., St John's, NL, A1B 3X9, Canada.
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Lupu DC, Monedero I, Rodriguez-Ruiz C, Pita M, Turiegano E. In support of 2D:4D: More data exploring its conflicting results on handedness, sexual orientation and sex differences. PLoS One 2023; 18:e0280514. [PMID: 37607180 PMCID: PMC10443882 DOI: 10.1371/journal.pone.0280514] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Accepted: 12/28/2022] [Indexed: 08/24/2023] Open
Abstract
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.
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Affiliation(s)
| | - Ignacio Monedero
- Departamento de Fisiología, Universidad Autónoma de Madrid, Madrid, España
| | | | - Miguel Pita
- Departamento de Biología, Universidad Autónoma de Madrid, Madrid, España
| | - Enrique Turiegano
- Departamento de Biología, Universidad Autónoma de Madrid, Madrid, España
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7
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Manning JT, Fink B. Digit ratio (2D:4D) and its relationship to foetal and maternal sex steroids: A mini-review. Early Hum Dev 2023; 183:105799. [PMID: 37300988 DOI: 10.1016/j.earlhumdev.2023.105799] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/12/2023] [Revised: 06/04/2023] [Accepted: 06/06/2023] [Indexed: 06/12/2023]
Abstract
The challenges of terrestrial existence may mean that the early development of tetrapod limb traits is linked to the development of the urogenital system and sex steroids. One such limb trait is the sex-dependent ratio of the lengths of the 2nd and 4th digits (2D:4D). Direct evidence for the association between early sex steroids and offspring 2D:4D can be obtained by manipulating foetal sex hormones. However, this is not ethically permissible in humans. It is widely accepted that 2D:4D is a biomarker for early foetal sex hormones in tetrapods but the link in humans remains controversial. Here we review the evidence that (i) manipulation of sex steroids in early development leads to sex-dependent changes in 2D:4D throughout the tetrapods, and (ii) maternal sex steroids cross the placenta and thus are associated with offspring 2D:4D in both non-human and human animals. We suggest a research focus on associations between human maternal sex steroids and offspring 2D:4D to clarify the link between 2D:4D and early sex steroids. A protocol is proposed to examine the correlation between 1st-trimester maternal sex steroids and offspring 2D:4D. Such an association may explain the existence and medium effect size of the human sex difference in 2D:4D.
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Affiliation(s)
- J T Manning
- Applied Sports, Technology, Exercise, and Medicine (A-STEM), Swansea University, Swansea, United Kingdom
| | - B Fink
- Department of Evolutionary Anthropology, University of Vienna, Austria; Human Evolution and Archaeological Sciences (HEAS), University of Vienna, Austria; Biosocial Science Information, Biedermannsdorf, Austria.
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8
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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. J Biosoc Sci 2023; 55:383-395. [PMID: 35088686 DOI: 10.1017/s0021932022000049] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
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.
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9
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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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10
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Swift-Gallant A, Shirazi T, Puts DA, Breedlove SM. Evidence for Perinatal Steroid Influence on Human Sexual Orientation and Gendered Behavior. Cold Spring Harb Perspect Biol 2022; 14:a039123. [PMID: 34872968 PMCID: PMC9341466 DOI: 10.1101/cshperspect.a039123] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
In laboratory animals, exposure to gonadal steroid hormones before and immediately after birth can exert permanent effects on many behaviors, particularly reproductive behaviors. The extent to which such effects occur in humans remains an open question, but several lines of evidence indicate that perinatal levels of both androgens and estrogens may affect adult human psychology and behavior, including sexual orientation and gender nonconformity. Some putative indicators of prenatal androgen exposure, including the ratio of the length of the index finger to that of the ring finger (2D:4D), have repeatedly indicated that lesbians, on average, were exposed to more prenatal androgens than straight women, suggesting that sufficient fetal androgen exposure predisposes a fetus to gynephilia (attraction to women) at maturity. The digit ratios of gay men do not differ from those of straight men, suggesting that prenatal androgen levels are not responsible for their androphilia (attraction to men). However, evidence that gay men who prefer an insertive anal sex role (ASR) have more masculine digit ratios than those preferring a receptive ASR suggests that early androgens influence some sexual preferences in men. Furthermore, digit ratios among gay men have been found to correlate with recalled childhood gender nonconformity (CGN). People with isolated gonadotropin-releasing hormone (GnRH) deficiency (IGD) offer further insight into the effects of perinatal gonadal steroid exposure. In people with IGD, gonadal hormone production is low or absent after the first trimester of gestation. However, because placental gonadotropins drive gonadal hormone secretion during the first trimester when genitalia sexually differentiate, individuals with IGD are unambiguously male or female at birth, consistent with their chromosomal and gonadal sex. Men with IGD report greater CGN, again suggesting that perinatal androgen exposure contributes to male-typical behavioral patterns in humans. Interestingly, women with IGD report less androphilia and more bisexuality than control women, suggesting that perinatal ovarian steroids in females typically augment androphilia in adulthood. Taken together, these findings indicate that the perinatal hormonal milieu influences human sexual orientation and gender conformity.
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Affiliation(s)
- Ashlyn Swift-Gallant
- Department of Psychology, Memorial University of Newfoundland, St. John's A1B 3X9, Newfoundland and Labrador
| | - Talia Shirazi
- Department of Anthropology, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - David A Puts
- Department of Anthropology, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - S Marc Breedlove
- Neuroscience Program, Michigan State University, East Lansing, Michigan 48824, USA
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Witczak LR, Arias Del Razo R, Baxter A, Conley AJ, Cotterman R, Dufek M, Goetze LR, Lau AR, Mendoza SP, Savidge LE, Bales KL. Relationships between cortisol and urinary androgens in female titi monkeys (Plecturocebus cupreus). Gen Comp Endocrinol 2021; 314:113927. [PMID: 34653435 PMCID: PMC9250648 DOI: 10.1016/j.ygcen.2021.113927] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/28/2020] [Revised: 10/04/2021] [Accepted: 10/09/2021] [Indexed: 01/16/2023]
Abstract
Steroid hormones are critical to the regulation of sociosexual behavior. Their role in the formation of pair bonds is complicated by the relative scarcity of this social system in mammals, as well as species and taxonomic differences in endocrine systems. In the present study, we experimentally manipulated the hypothalamic-pituitary-adrenal axis in female titi monkeys (Plecturocebus cupreus), a neotropical monkey studied for its strong, selective pair bonds. We validated an assay for plasma and urinary cortisol in this species, showing a strong suppression of cortisol following dexamethasone injection, and a significant but somewhat blunted response to adrenocorticotrophin hormone (ACTH) stimulation. Urinary androgens did not change in response to dexamethasone or ACTH. Plasma and urinary cortisol were moderately correlated, whereas urinary cortisol and androgens were only correlated when extreme cortisol values were included. In this study, we laid groundwork for studying the role of glucocorticoids and androgens (and eventually, their interactions with peptides) in the behavioral endocrinology of pair bonds in female titi monkeys.
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Affiliation(s)
- Lynea R Witczak
- Department of Psychology, University of California, Davis, United States; California National Primate Research Center, University of California, Davis, United States
| | - Rocío Arias Del Razo
- Department of Psychology, University of California, Davis, United States; California National Primate Research Center, University of California, Davis, United States
| | - Alexander Baxter
- Department of Psychology, University of California, Davis, United States; California National Primate Research Center, University of California, Davis, United States
| | - Alan J Conley
- Department of Population Health and Reproduction, University of California, Davis, United States
| | - Rebecca Cotterman
- Department of Population Health and Reproduction, University of California, Davis, United States
| | - Madison Dufek
- California National Primate Research Center, University of California, Davis, United States
| | - Leana R Goetze
- California National Primate Research Center, University of California, Davis, United States
| | - Allison R Lau
- California National Primate Research Center, University of California, Davis, United States; Graduate Program in Animal Behavior, University of California, Davis, United States
| | - Sally P Mendoza
- Department of Psychology, University of California, Davis, United States; California National Primate Research Center, University of California, Davis, United States
| | - Logan E Savidge
- Department of Psychology, University of California, Davis, United States; California National Primate Research Center, University of California, Davis, United States
| | - Karen L Bales
- Department of Psychology, University of California, Davis, United States; California National Primate Research Center, University of California, Davis, United States; Department of Neurobiology, Physiology, and Behavior, University of California, Davis, United States; Graduate Program in Animal Behavior, University of California, Davis, United States.
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12
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Parental income inequality and children's digit ratio (2D:4D): a 'Trivers-Willard' effect on prenatal androgenization? J Biosoc Sci 2021; 54:154-162. [PMID: 33557976 DOI: 10.1017/s0021932021000043] [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: 11/07/2022]
Abstract
Income inequality is associated positively with disease prevalence and mortality. Digit ratio (2D:4D) - a negative proxy for prenatal testosterone and a positive correlate of prenatal oestrogen - is related to several diseases. This study examined the association of income inequality (operationalized as relative parental income) and children's 2D:4D. Participants self-measured finger lengths (2D=index finger, and 4D=ring finger) in a large online survey conducted in July 2005 (the BBC Internet Study) and reported their parents' income. Children of parents of above-average income had low 2D:4D (high prenatal testosterone, low prenatal oestrogen) while the children of parents of below-average income had high 2D:4D (low prenatal testosterone, high prenatal oestrogen). The effects were significant in the total sample, present among Whites (the largest group in the sample), in the two largest national samples (UK and USA) and were greater for males than females. The findings suggest a Trivers-Willard effect, such that high-income women may prenatally masculinize their sons at the expense of the fitness of their daughters. Women with low income may prenatally feminize their daughters at the fitness expense of their sons. The effect could, in part, explain associations between low income, high 2D:4D (low prenatal testosterone) and some major causes of mortality such as cardiovascular disease.
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13
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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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14
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Wood EK, Jarman P, Cash E, Baxter A, Capitanio JP, Higley JD. Masculinized Second-to-Fourth Digit Ratio (2D:4D Ratio) Is Associated With Lower Cortisol Response in Infant Female Rhesus Monkeys ( Macaca mulatta). Front Behav Neurosci 2020; 14:94. [PMID: 33088262 PMCID: PMC7497207 DOI: 10.3389/fnbeh.2020.00094] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2020] [Accepted: 05/18/2020] [Indexed: 01/02/2023] Open
Abstract
The second-to-fourth digit ratio (2D:4D ratio) is considered a postnatal proxy measure for the degree of prenatal androgen exposure (PAE), which is the primary factor responsible for masculinizing the brain of a developing fetus. Some studies suggest that the organizational effects of PAE may extend to the hypothalamic-pituitary-adrenal (HPA) axis response to stress. This study investigates the relationship between 2D:4D ratio and HPA axis functioning using a rhesus monkey (Macaca mulatta) model. Subjects were N = 268 (180 females, 88 males) rhesus monkey infants (3–4 months of age). Plasma cortisol concentrations were assayed from two blood samples obtained during a 25-h experimental social separation stressor at 2- and 7-h post-separation. Subjects’ 2D:4D ratio was measured later in life (Mage = 6.70 years). It was hypothesized that infant rhesus monkeys that exhibited a more masculine-like 2D:4D ratio would show lower levels of circulating cortisol after a social separation and relocation stressor. The results showed that there was a sex difference in the left-hand 2D:4D ratio. The results also showed that there was an overall sex difference in cortisol concentrations and that female, but not male, monkeys that exhibited a more masculine-like right- and left-hand 2D:4D ratio exhibited lower mean stress-induced cortisol concentrations early in life. These findings suggest that higher levels of prenatal androgens in females, as measured by 2D:4D ratio, may be related to an attenuated HPA axis stress-response, as measured by plasma cortisol levels. To the extent that these findings generalize to humans, they suggest that the organizational effects of PAE extend to the infant HPA axis, modulating the HPA axis response, particularly in females.
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Affiliation(s)
- Elizabeth K Wood
- Department of Psychology, Brigham Young University, Provo, UT, United States
| | - Parker Jarman
- Department of Psychology, Brigham Young University, Provo, UT, United States
| | - Elysha Cash
- Department of Psychology, Brigham Young University, Provo, UT, United States
| | - Alexander Baxter
- Department of Psychology, University of California, Davis, Davis, CA, United States.,California National Primate Research Center (CNPRC), Davis, CA, United States
| | - John P Capitanio
- Department of Psychology, University of California, Davis, Davis, CA, United States.,California National Primate Research Center (CNPRC), Davis, CA, United States
| | - J Dee Higley
- Department of Psychology, Brigham Young University, Provo, UT, United States
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15
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Depression, neuroticism and 2D:4D ratio: evidence from a large, representative sample. Sci Rep 2020; 10:11136. [PMID: 32636433 PMCID: PMC7341800 DOI: 10.1038/s41598-020-67882-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2020] [Accepted: 06/01/2020] [Indexed: 02/08/2023] Open
Abstract
A body of literature reports higher rates of depression and neuroticism in female samples compared to male samples. Numerous studies have investigated the role of prenatal sex hormone exposure in this sex difference, using the ratio between the second and fourth digit of the hand (“2D:4D”) as a putative marker. However, the sample sizes of those studies were mostly small and results remained inconclusive. The aim of the present study is to test the suggested associations between depression, neuroticism and the 2D:4D ratio in a large, representative sample of over 3,000 German individuals. It was hypothesized that a higher 2D:4D (supposedly representing a more “feminine” prenatal hormone exposure) would positively predict (1) one’s history of depression as well as (2) neuroticism rates and (3) acute depressive symptom scores. Controlling for biological sex, we only found suggestive evidence for linear associations with neuroticism in the case of left hand 2D:4D ratios and the mean 2D:4D of both hands. However, additional analyses indicated that these results may have been spurious due to confounding. Our findings suggest that the 2D:4D ratio is not a relevant predictor of depression, while there was mixed evidence in the case of neuroticism.
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16
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Swift-Gallant A, Johnson BA, Di Rita V, Breedlove SM. Through a glass, darkly: Human digit ratios reflect prenatal androgens, imperfectly. Horm Behav 2020; 120:104686. [PMID: 32014464 DOI: 10.1016/j.yhbeh.2020.104686] [Citation(s) in RCA: 53] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Accepted: 01/09/2020] [Indexed: 01/07/2023]
Abstract
On average, the length of the index finger (digit 2) divided by the length of the ring finger (digit 4) on the right hand, is greater in women than in men. Converging evidence makes it clear that prenatal androgens affect the development of digit ratios in humans and so are likely responsible for this sex difference. Thus, differences in 2D:4D between groups within a sex may be due to average differences between those groups in prenatal androgen exposure. There have been many reports that lesbians, on average, have a smaller (more masculine) digit ratio than straight women, which has been confirmed by metaanalysis. These findings indicate that lesbians were, on average, exposed to greater prenatal androgen than straight women, which further indicates that greater levels of prenatal androgen predispose humans to be attracted to women in adulthood. Nevertheless, these results only apply to group differences between straight women and lesbians; digit ratios cannot be used to classify individual women as gay or straight.
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Affiliation(s)
- Ashlyn Swift-Gallant
- Department of Psychology, Memorial University of Newfoundland, St. Johns, NL A1B 3X9, Canada
| | - Brandon A Johnson
- Neuroscience Program, Michigan State University, United States of America
| | - Victor Di Rita
- Neuroscience Program, Michigan State University, United States of America
| | - S Marc Breedlove
- Neuroscience Program, Michigan State University, United States of America; Department of Psychology, Michigan State University, United States of America.
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