Sexual differentiation of the human brain in relation to gender identity and sexual orientation

Sex versus gender associations with brain structure

In contrast to sex (a biological distinction), little is known about the associations between gender (a societal construct) and brain structure in the general population. In response to this knowledge gap, we examined the associations of sex vs. gender with FreeSurfer-generated cortical thickness and proportion-adjusted subcortical brain volume regions-of-interest (ROIs) in healthy adults (n = 88) screened for general medical conditions, mental illness, substance abuse, and intracranial pathologies. Gender role endorsement was assessed using the well-established and validated Bem Sex Role Inventory. For our main objectives, we calculated a continuum score as a composite measure of gender. For our secondary objectives, we examined sex-specific associations of the masculine vs. feminine gender role endorsement domains with brain structural outcomes. We found that female sex, independent of continuum scores, was associated with larger proportion-adjusted volumes for the basal ganglia, hippocampus, and ventral diencephalon. Higher continuum scores, independent of sex, were associated with thicker cortical thickness for the left and right superior frontal cortex, caudal and rostral middle frontal cortex, and right pars orbitalis. Female sex and higher continuum scores were independently associated with larger corpus callosum volumes. Post-hoc testing showed sex-specific associations between higher femininity scores and thicker prefrontal cortical thickness for the ROIs in females, but not in males. In conclusion, sex and gender showed semi-independent associations with brain structure in a general population sample. Our research supports the disaggregation of sex and gender to provide a more nuanced perspective on brain structural differences between men and women.

After the trans brain: a critique of the neurobiological accounts of embodied trans* identities

This paper critically analyses three main neurobiological hypotheses on trans* identities: the neurobiological theory about the origin of gender dysphoria, the neurodevelopmental cortical hypothesis, and the alternative hypothesis of self-referential thinking and body perception. In this study I focus then the attention on three elements: the issue of (de)pathologisation, the idea of the trans brain, and the aetiology of trans* identities. While the neurobiological theory about the origin of gender dysphoria and the neurodevelopmental cortical hypothesis claim the existence of the trans brain, each offering its own neurobiological depiction, the hypothesis of self-referential thinking and body perception doesn't postulate a distinctive neurobiological trait for all trans* people. I problematize both portrayals of the trans brain departing from the findings and conceptualizations of the paradigm shifting brain mosaicism. Unlike the hypothesis of self-referential thinking and body perception that keeps the question of causation open, both the neurobiological theory about the origin of gender dysphoria and the neurodevelopmental cortical hypothesis situate the origin of trans* identities in the neurobiological domain. I challenge the biological deterministic framework in which this aetiology is inscribed from a dynamic processual entanglement perspective. Finally, concerning the issue of (de)pathologisation of trans* identities, an evolution can be seen in each of the hypothesis and among them, from the least to the most depathologising. However, I question their complete departure from a pathologising framework.

Accurate machine learning prediction of sexual orientation based on brain morphology and intrinsic functional connectivity

BACKGROUND

Sexual orientation in humans represents a multilevel construct that is grounded in both neurobiological and environmental factors.

OBJECTIVE

Here, we bring to bear a machine learning approach to predict sexual orientation from gray matter volumes (GMVs) or resting-state functional connectivity (RSFC) in a cohort of 45 heterosexual and 41 homosexual participants.

METHODS

In both brain assessments, we used penalized logistic regression models and nonparametric permutation.

RESULTS

We found an average accuracy of 62% (±6.72) for predicting sexual orientation based on GMV and an average predictive accuracy of 92% (±9.89) using RSFC. Regions in the precentral gyrus, precuneus and the prefrontal cortex were significantly informative for distinguishing heterosexual from homosexual participants in both the GMV and RSFC settings.

CONCLUSIONS

These results indicate that, aside from self-reports, RSFC offers neurobiological information valuable for highly accurate prediction of sexual orientation. We demonstrate for the first time that sexual orientation is reflected in specific patterns of RSFC, which enable personalized, brain-based predictions of this highly complex human trait. While these results are preliminary, our neurobiologically based prediction framework illustrates the great value and potential of RSFC for revealing biologically meaningful and generalizable predictive patterns in the human brain.

Sex differences in neuroimmunoendocrine communication. Involvement on longevity

Endocrine, nervous, and immune systems work coordinately to maintain the global homeostasis of the organism. They show sex differences in their functions that, in turn, contribute to sex differences beyond reproductive function. Females display a better control of the energetic metabolism and improved neuroprotection and have more antioxidant defenses and a better inflammatory status than males, which is associated with a more robust immune response than that of males. These differences are present from the early stages of life, being more relevant in adulthood and influencing the aging trajectory in each sex and may contribute to the different life lifespan between sexes.

A Gender-Based Point of View in Pediatric Neurology

While the significance of gender has only recently been recognized, gender assigned at birth has long been understood to have a significant influence on a number of illnesses. Due to the paucity of data in this regard in pediatrics, the purpose of this narrative review is to frame the most recent knowledge about the role of gender assigned at birth in the neurological development and neuropsychiatric disorders among young people. Literature analysis showed that gender disparities exist in neurologic and neuropsychiatric disorders among the pediatric population and supported the fact that new guidelines should take this into account. However, there is an urgent need for specific studies focused on gender role among children and adolescents in order to better understand how this can relate to diagnosis, development and treatment of different neurologic and neuropsychiatric diseases. Moreover, further efforts should be directed to identify unique risks linked to gender disorders and gender dysphoria as well as taking into account a gender point of view when approaching a pediatric patient.

Gender incongruence and timing of puberty: a population-based cohort study

OBJECTIVE

To study whether the timing of puberty in adolescents who reported gender incongruence (incongruence between birth-assigned sex and self-identified gender) was different from those adolescents who reported gender congruence.

DESIGN

Population-based cohort study using data from the Danish National Birth Cohort.

SETTING

Not applicable.

PATIENT(S)

Birth-assigned boys and girls born between 2000 and 2003, who self-reported gender incongruence at 11 years (N = 10,046) and their pubertal developmental stages from age 11 years to every 6 months throughout puberty were included.

INTERVENTION(S)

Not applicable.

MAIN OUTCOME MEASURE

Mean age differences in months at reaching Tanner stages 2-5 for breast or genital development and pubic hair, voice break, first ejaculation, menarche, axillary hair, acne, and the average difference at attaining all pubertal milestones (primary outcome).

RESULT(S)

In total, 549 (5.5% ) adolescents reported part or full gender incongruence at 11 years. Tendencies toward earlier timing of puberty were observed in adolescents who reported part gender incongruence (average difference, birth-assigned boys: -3.2 months [95% confidence interval {CI}: -6.7; 0.3]; birth-assigned girls: -2.0 months [95% CI: -3.9; -0.1]). Tendencies toward earlier timing of puberty were observed in adolescents who reported full gender incongruence (average difference, birth-assigned boys: -2.4 months [95% CI: -5.0; 0.4]; birth-assigned girls: -1.9 months [95% CI: -5.1; 1.2]).

CONCLUSIONS

The results from this study indicated that birth-assigned boys and girls who reported either part or full gender incongruence tended to reach puberty slightly earlier than those adolescents who reported gender congruence at 11 years of age. Knowledge on the timing of puberty among adolescents who experience gender incongruence is essential to inform mutual decision-making in clinical settings.

Ontogenetic rules for the molecular diversification of hypothalamic neurons

The hypothalamus is an evolutionarily conserved endocrine interface that, among other roles, links central homeostatic control to adaptive bodily responses by releasing hormones and neuropeptides from its many neuronal subtypes. In its preoptic, anterior, tuberal and mammillary subdivisions, a kaleidoscope of magnocellular and parvocellular neuroendocrine command neurons, local-circuit neurons, and neurons that project to extrahypothalamic areas are intermingled in partially overlapping patches of nuclei. Molecular fingerprinting has produced data of unprecedented mass and depth to distinguish and even to predict the synaptic and endocrine competences, connectivity and stimulus selectivity of many neuronal modalities. These new insights support eminent studies from the past century but challenge others on the molecular rules that shape the developmental segregation of hypothalamic neuronal subtypes and their use of morphogenic cues for terminal differentiation. Here, we integrate single-cell RNA sequencing studies with those of mouse genetics and endocrinology to describe key stages of hypothalamus development, including local neurogenesis, the direct terminal differentiation of glutamatergic neurons, transition cascades for GABAergic and GABAergic cell-derived dopamine cells, waves of local neuronal migration, and sequential enrichment in neuropeptides and hormones. We particularly emphasize how transcription factors determine neuronal identity and, consequently, circuit architecture, and whether their deviations triggered by environmental factors and hormones provoke neuroendocrine illnesses.

Should chromosomal analysis be performed routinely during the baseline evaluation of the gender affirmation process? The outcomes of a large cohort of gender dysphoric individuals

The role of genetics in the etiology of gender dysphoria (GD) is an important yet understudied area. Yet whether genetic analysis should be carried out during the gender affirmation process at all is a matter of debate. This study aims to evaluate the cytogenetic and molecular genetic findings of individuals with GD. We retrospectively reviewed the medical records of individuals with GD who were followed up in a tertiary clinic. After the exclusion criteria were applied, the study sample consisted of 918 individuals with GD; 691 of whom had female-to-male (FtM) and 227 male-to-female (MtF) GD. The cytogenetic analysis revealed that 223 out of 227 (98.2%) individuals with MtF GD had the 46,XY karyotype, while 683 out of 691 (98.8%) individuals with FtM GD had the 46,XX karyotype. In the Y chromosome microdeletion analysis, azospermic factor c (AZFc) deletion was detected in only two individuals with MtF GD. Our findings suggest that there are few chromosomal abnormalities in individuals with GD. Thus, this research calls into question both the role of chromosomal abnormalities in GD etiology and why the application of chromosomal analysis is in Turkey a routine part of the baseline evaluation of GD.

Brain Sex in Transgender Women Is Shifted towards Gender Identity

Transgender people report discomfort with their birth sex and a strong identification with the opposite sex. The current study was designed to shed further light on the question of whether the brains of transgender people resemble their birth sex or their gender identity. For this purpose, we analyzed a sample of 24 cisgender men, 24 cisgender women, and 24 transgender women before gender-affirming hormone therapy. We employed a recently developed multivariate classifier that yields a continuous probabilistic (rather than a binary) estimate for brains to be male or female. The brains of transgender women ranged between cisgender men and cisgender women (albeit still closer to cisgender men), and the differences to both cisgender men and to cisgender women were significant (p = 0.016 and p < 0.001, respectively). These findings add support to the notion that the underlying brain anatomy in transgender people is shifted away from their biological sex towards their gender identity.

Hormones and Sex-Specific Medicine in Human Physiopathology

A prodigious increment of scientific evidence in both preclinical and clinical studies is narrowing a major gap in knowledge regarding sex-specific biological responses observed in numerous branches of clinical practices. Some paradigmatic examples include neurodegenerative and mental disorders, immune-related disorders such as pathogenic infections and autoimmune diseases, oncologic conditions, and cardiovascular morbidities. The male-to-female proportion in a population is expressed as sex ratio and varies eminently with respect to the pathophysiology, natural history, incidence, prevalence, and mortality rates. The factors that determine this scenario incorporate both sex-associated biological differences and gender-dependent sociocultural issues. A broad narrative review focused on the current knowledge about the role of hormone regulation in gender medicine and gender peculiarities across key clinical areas is provided. Sex differences in immune response, cardiovascular diseases, neurological disorders, cancer, and COVID-19 are some of the hints reported. Moreover, gender implications in occupational health and health policy are offered to support the need for more personalized clinical medicine and public health approaches to achieve an ameliorated quality of life of patients and better outcomes in population health.

Neuroradiology in Transgender Care: Facial Feminization, Laryngeal Surgery, and Beyond

Transgender individuals experience incongruence between their gender identity and the sex assigned to them at birth. This incongruence can cause many transgender individuals to experience distressing physical and mental discord, a diagnosis known as gender dysphoria. Craniofacial structures have distinct anthropometric characteristics that affect perceived masculinity and femininity. The face, neck, and voice are highly exposed anatomic areas that have recognizable gender-specific characteristics that may hinder a transgender individual's successful social integration and public acceptance. Reconstructive facial and laryngeal procedures are among the surgical options transgender persons may elect to undergo to better align their physical appearance with their gender identity. These include feminization surgeries such as facial feminization and reduction chondrolaryngoplasty, as well as masculinizing facial and laryngeal surgeries. Maxillofacial CT is frequently used in the preoperative evaluation of patients before facial feminization surgery (FFS). Several CT measurements guide surgeons to the optimal correction required in FFS to achieve appropriate aesthetic planes. Mapping important craniofacial landmarks to avoid untoward surgical complications is crucial. Transgender patients may encounter other neurologic complications that require neuroimaging evaluation. For example, gender-affirming hormone therapy (eg, estrogen and testosterone) may increase the risk of stroke or may influence growth of various hormone-sensitive tumors such as pituitary adenomas. Radiologists may interpret imaging examinations in transgender patients for routine care or for evaluation before and after facial and laryngeal surgeries and must be aware of the role of neuroimaging in the care of this population. An invited commentary by Callen is available online. The online slide presentation from the RSNA Annual Meeting is available for this article. ^©RSNA, 2022.

Structural, Functional, and Metabolic Brain Differences as a Function of Gender Identity or Sexual Orientation: A Systematic Review of the Human Neuroimaging Literature

This review systematically explored structural, functional, and metabolic features of the cisgender brain compared with the transgender brain before hormonal treatment and the heterosexual brain compared to the homosexual brain from the analysis of the neuroimaging literature up to 2018, and identified and discussed subsequent studies published up to March 2021. Our main aim was to help identifying neuroradiological brain features that have been related to human sexuality to contribute to the understanding of the biological elements involved in gender identity and sexual orientation. We analyzed 39 studies on gender identity and 24 on sexual orientation. Our results suggest that some neuroanatomical, neurophysiological, and neurometabolic features in transgender individuals resemble those of their experienced gender despite the majority resembling those from their natal sex. In homosexual individuals the majority resemble those of their same-sex heterosexual population rather than their opposite-sex heterosexual population. However, it is always difficult to interpret findings with noninvasive neuroimaging. Given the gross nature of these measures, it is possible that more differences too subtle to measure with available tools yet contributing to gender identity and sexual orientation could be found. Conflicting results contributed to the difficulty of identifying specific brain features which consistently differ between cisgender and transgender or between heterosexual and homosexual groups. The small number of studies, the small-to-moderate sample size of each study, and the heterogeneity of the investigations made it impossible to meta-analyze all the data extracted. Further studies are necessary to increase the understanding of the neurological substrates of human sexuality.

Sex, gender and gender identity: a re-evaluation of the evidence

In the past decade there has been a rapid increase in gender diversity, particularly in children and young people, with referrals to specialist gender clinics rising. In this article, the evolving terminology around transgender health is considered and the role of psychiatry is explored now that this condition is no longer classified as a mental illness. The concept of conversion therapy with reference to alternative gender identities is examined critically and with reference to psychiatry's historical relationship with conversion therapy for homosexuality. The authors consider the uncertainties that clinicians face when dealing with something that is no longer a disorder nor a mental condition and yet for which medical interventions are frequently sought and in which mental health comorbidities are common.

Cortical Gyrification in Transgender Individuals

Gender incongruence (GI) is characterized by a feeling of estrangement from the own body in the context of self. GI is often described in people who identify as transgender. The underlying mechanisms are unknown. Data from MRI measurements and tests of own body perception triggered us to pose a model that GI in transgender persons (TGI) could be associated with a disconnection within the brain circuits mediating the perception of own body as self. This is a departure from a previous model of sex atypical cerebral dimorphism, introducing a concept that better accords with a core feature of TGI. The present MRI study of 54 hormone naive transmen (TrM), 38 transwomen (TrW), 44 cismen and 41 ciswomen show that cortical gyrification, a metric that reflects early maturation of cerebral cortex, is significantly lower in transgender compared with cisgender participants. This reduction is limited to the occipito-parietal cortex and the sensory motor cortex, regions encoding own body image and body ownership. Moreover, the cortical gyrification correlated inversely with own body-self incongruence in these regions. These novel data suggest that GI in TGI may originate in the neurodevelopment of body image encoding regions. The results add potentially to understanding neurobiological contributors to gender identity.

Sex Matters: A Multivariate Pattern Analysis of Sex- and Gender-Related Neuroanatomical Differences in Cis- and Transgender Individuals Using Structural Magnetic Resonance Imaging

Univariate analyses of structural neuroimaging data have produced heterogeneous results regarding anatomical sex- and gender-related differences. The current study aimed at delineating and cross-validating brain volumetric surrogates of sex and gender by comparing the structural magnetic resonance imaging data of cis- and transgender subjects using multivariate pattern analysis. Gray matter (GM) tissue maps of 29 transgender men, 23 transgender women, 35 cisgender women, and 34 cisgender men were created using voxel-based morphometry and analyzed using support vector classification. Generalizability of the models was estimated using repeated nested cross-validation. For external validation, significant models were applied to hormone-treated transgender subjects (n = 32) and individuals diagnosed with depression (n = 27). Sex was identified with a balanced accuracy (BAC) of 82.6% (false discovery rate [pFDR] < 0.001) in cisgender, but only with 67.5% (pFDR = 0.04) in transgender participants indicating differences in the neuroanatomical patterns associated with sex in transgender despite the major effect of sex on GM volume irrespective of the self-identification as a woman or man. Gender identity and gender incongruence could not be reliably identified (all pFDR > 0.05). The neuroanatomical signature of sex in cisgender did not interact with depressive features (BAC = 74.7%) but was affected by hormone therapy when applied in transgender women (P < 0.001).

2D:4D Digit Ratios in Adults with Gender Dysphoria: A Comparison to Their Unaffected Same-Sex Heterosexual Siblings, Cisgender Heterosexual Men, and Cisgender Heterosexual Women

We compared gender dysphoria (GD) patients and their same-sex siblings in terms of their 2D:4D ratios, which may reflect prenatal exposure to androgen, one of the possible etiological mechanisms underlying GD. Sixty-eight GD patients (46 Female-to-Male [FtM]; 22 Male-to-Female [MtF]), 68 siblings (46 sisters of FtMs; 22 brothers of MtFs), and 118 heterosexual controls (62 female; 56 male) were included in the study. FtMs were gynephilic and MtFs were androphilic. We found that 2D:4D ratios in the both right hand (p < .001) and the left hand (p = .003) were lower in male controls than in female controls. Regarding right hands, FtM GD patients had lower 2D:4D ratios than female controls (p < .001) but their ratios did not differ from those of their sisters or male controls. FtM GD patients had no significant difference in their left-hand 2D:4D ratios compared to their sisters or female and male controls. While there was no significant difference in right hands between FtM's sisters and male controls, left-hand 2D:4D ratios were significantly higher in FtM's sisters (p = .017). MtF GD patients had lower right-hand 2D:4D ratios than female controls (p <.001), but their right-hand ratios did not differ from those of their brothers and male controls. There was no significant difference in left-hand 2D:4D ratios between MtF GD patients, and their brothers, or female and male controls. FtM GD patients showed significantly masculinized right-hand 2D:4D ratios, while there was no evidence of feminization in MtF GD patients.

Epistemic Injustice in Brain Studies of (Trans)Gender Identity

This study undertakes an analysis of the conceptualization of gender identity in neuroscientific studies of (trans)gender identity that contrast the brains of cisgender and transgender participants. The analysis focuses on instances of epistemic injustice that combine scientific deficiencies and the exclusion of relevant bodies of knowledge. The results of a content analysis show how the ignoring of biosocial, developmental, mosaicist, contextualist, and depathologizing approaches leads to internal conceptual inconsistencies, hermeneutical deficiencies and the upholding of questionable paradigms in the research field. Interviews with researchers involved in these brain studies reveal targeted and diffuse forms of testimonial injustice against alternative approaches, promoted by the hierarchical arrangements of research teams in combination with the careerist and economic logic of research. The analysis points to the exclusion of critical epistemologies of science and the historical oppression of trans people as epistemic agents as the underlying hermeneutical deficiencies.

Male Ejaculatory Endophenotypes: Revealing Internal Inconsistencies of the Concept in Heterosexual Copulating Rats

Distinct manifestations of sexual behavior are conceived as separate phenotypes. Each sexual phenotype is assumed to be associated with a characteristic brain. These notions have justified the phenotyping of heterosexual copulator males based upon their ejaculation's latencies (EL) or frequencies (i.e., cumulative ejaculation number; EN). For instance, men and male rats showing premature, normal or retarded ejaculation are assumed to be distinctive endophenotypes. This concept, nonetheless, contradicts past and recent evidence that supports that sexual behavior is highly variable within each sex, and that the brain sexual functional morphology represents an intricate sexual phenotypic mosaic. Hence, for ejaculatory male endophenotypes to be considered as a valid biological concept, it must show internal consistency at various levels of organization (including genetic architectures), after being challenged by intrinsic and/or extrinsic factors. We then judged the internal consistency of the presumed ejaculatory endophenotypes by assessing whether copulatory behavior and the expression of copulation relevant genes and brain limbic structures are specific to each of the presumed EL- or EN-ejaculatory endophenotypes. To do this, copulating male rats were first phenotyped in groups consistently displaying short, average or long ejaculation latencies or very high, high, average, low or very low EN, based in their copulatory performance. Then, the internal consistency of the presumed EL- or EN-endophenotypes was tested by introducing as covariates of phenotyping other copulatory parameters (e.g., number of intromissions) in addition to EL or EN, or by analyzing the expression levels of genes encoding for estrogen receptor alpha, progesterone receptor, androgen receptor, aromatase, DNA methyl-transferase 3a and DNA methyl-transferase 1 in the amygdala, medial preoptic area, ventromedial hypothalamus and olfactory bulb. We found that even though there were group-level differences in all the variables that were studied, these differences did not add-up to create the presumed EL- or EN-ejaculatory endophenotypes. In fact, the extensive overlapping of copulatory parameters and expression levels of copulation relevant genes in limbic structures across EL- or EN-phenotyped copulating male rats, is not consistent with the hypothesis that distinct ejaculatory endophenotypes exist and that they are associated with specific brain characteristics.

Sexual Orientation in Individuals With Congenital Adrenal Hyperplasia: A Systematic Review

Congenital adrenal hyperplasia (CAH) is a genetic condition of the steroidogenic enzymes in the adrenal cortex normally leading to variable degrees of cortisol and aldosterone deficiency as well as androgen excess. Exposure to androgens prenatally might lead to ambiguous genitalia. The fetal brain develops in traditional male direction through a direct action of androgens on the developing nerve cells, or in the traditional female direction in the absence of androgens. This may indicate that sexual development, including sexual orientation, are programmed into our brain structures prenatally. The objective of this study was to perform a systematic review of the literature, investigating sexual orientation in individuals with CAH. The study also aimed at identifying which measures are used to define sexual orientation across studies. The review is based on articles identified through a comprehensive search of the OVIDMedline, PsycINFO, CINAHL, and Web of Science databases published up to May 2019. All peer-reviewed articles investigating sexual orientation in people with CAH were included. Quantitative, qualitative, and mixed methods were considered, as well as self-, parent-, and third-party reports, and no age or language restrictions were enforced on publications. The present review included 30 studies investigating sexual orientation in patients with CAH assigned female at birth (46, XX) (n = 927) or assigned male at birth (46, XY and 46, XX) (n = 274). Results indicate that assigned females at birth (46, XX) with CAH had a greater likelihood to not have an exclusively heterosexual orientation than females from the general population, whereas no assigned males at birth (46, XY or 46, XX) with CAH identified themselves as non-heterosexual. There was a wide diversity in measures used and a preference for unvalidated and self-constructed interviews. Hence, the results need to be interpreted with caution. Methodological weaknesses might have led to non-heterosexual orientation being overestimated or underestimated. The methodological challenges identified by this review should be further investigated in future studies.

The Evolving Role of Pharmacists in Transgender Health Care

Pharmacists are increasingly part of a multifaceted team providing health care to members of the often marginalized transgender (TG) community. Some pharmacists, however, may feel unprepared to care for and interact with TG individuals. By providing comprehensive, respectful, and gender-affirming support, improving physical pharmacy environments with policies and procedures, pharmacists can be trustworthy providers for TG patients. This review focuses primarily on the health issues of TG persons and the pharmacist's role in promoting health, identifying barriers to health care, and providing health care resources for TG persons. The evolution of psychiatric diagnostic criteria, access to health care, and inclusion of TG, lesbian, gay, and bisexual topics in the educational curriculum are presented. Cultural competency and diversity training that addresses gender identity and sexual orientation issues should be important interdisciplinary and interprofessional activities for all health care professional education programs. Pharmacists play a key role in the health care needs of TG persons that include appropriate laboratory monitoring, complex pharmacotherapeutic challenges, and providing unbiased gender-affirming interactions. The pharmacy's physical environment, staff training, and policies and procedures can offer unique services to TG persons.

Combined exercise is a modality for improving insulin resistance and aging-related hormone biomarkers in elderly Korean women

BACKGROUND

The functional decline of the endocrine and immune systems with aging causes changes in the regulation of the body's metabolism and defense functions. Although it is impossible to stop aging artificially, regular exercises reportedly delay aging and have positive effects on senile diseases. The improvements in insulin resistance values and aging-related hormones in elderly women after combined exercises have not been effectively elucidated.

OBJECTIVE

In this study, we aimed to examine the impact of combined exercise on insulin resistance and aging-related hormones in elderly women.

METHODS

Twenty elderly Korean women were randomly assigned to a "non-exercise" (n = 10) or combined exercise group (n = 10). The exercise group performed both anaerobic and aerobic exercises for 12 weeks, three times per week. Exercise intensity was increased gradually, from 40% to 70% of the heart rate reserve (HRR) every 3 weeks. Insulin resistance, growth hormone, IGF-1, DHEA-S, and estrogen were measured before and after the 12-week intervention.

RESULTS

The main effect was found in the glucose level for a time, which significantly decreased in the exercise group. The insulin level and HOMA-IR showed significant interaction effects and increased significantly in the control group. The GH level showed significant interaction effects and increased significantly in the exercise group. The IGF-1 level showed significant interaction effects, but not significantly within and between groups. The DHEA-S level revealed interaction effects and the main effect for a time and significantly increased in the exercise group. The estrogen level exhibited an interaction effect and increased significantly in the exercise group. After the 12-week combined exercise intervention, no significant difference was observed between groups.

DISCUSSION

This study has shown that 12-week combined exercise is useful for improving insulin resistance and GH, IGF-1, and DHEA-S levels in elderly women. Thus, this study provides evidence that combined exercise is a useful therapeutic method to decrease insulin resistance and stimulate the secretion of aging-related hormones in elderly women.

Untangling the Gordian Knot of Human Sexuality

There is increasing interest in and tolerance of the lay public for variations in human sexuality. In contrast, the molecular biology that underlies gender identity, the development of gonadal and genital anatomy, and the factors that define sexual behavior is proving unexpectedly complex and is still incompletely understood. It is now evident that humans cannot be characterized as member of 1 of 2 clearly defined units: male or female. In fact, individuals exist on a continuum: those who do not conform unequivocally to the dyadic view of human sex in terms of anatomy, gender identity, and/or sexual behavior should be characterized as having variations in rather than disorders of sexual development. Such individuals can no longer be regarded as anomalies to be rejected, condemned, and, if possible, “corrected” either psychologically or anatomically.

Prenatal lead exposure in relation to age at menarche: results from a longitudinal study in Mexico City

Animal and cross-sectional epidemiological studies suggest that prenatal lead exposure is related to delayed menarche, but this has not been confirmed in longitudinal studies. We analyzed this association among 200 girls from Mexico City who were followed since the first trimester of gestation. Maternal blood lead levels were analyzed once during each trimester of pregnancy, and daughters were asked about their first menstrual cycle at a visit between the ages of 9.8 and 18.1 years. We estimated hazard ratios (HRs) and 95% confidence intervals (CI) for probability of menarche over the follow-up period using interval-censored Cox models, comparing those with prenatal blood lead level ⩾5 µg/dl to those with prenatal blood lead <5 µg/dl. We also estimated HRs and 95% CI with conventional Cox regression models, which utilized the self-reported age at menarche. In adjusted analyses, we accounted for maternal age, maternal parity, maternal education, and prenatal calcium treatment status. Across trimesters, 36-47% of mothers had blood lead levels ⩾5 µg/dl. Using interval-censored models, we found that during the second trimester only, girls with ⩾5 µg/dl prenatal blood lead had a later age at menarche compared with girls with prenatal blood lead levels <5 µg/dl (confounder-adjusted HR=0.59, 95% CI 0.28-0.90; P=0.05). Associations were in a similar direction, although not statistically significant, in the conventional Cox regression models, potentially indicating measurement error in the self-recalled age at menarche. In summary, higher prenatal lead exposure during the second trimester could be related to later onset of sexual maturation.

Neurobiology of gender identity and sexual orientation

Sexual identity and sexual orientation are independent components of a person's sexual identity. These dimensions are most often in harmony with each other and with an individual's genital sex, although not always. The present review discusses the relationship of sexual identity and sexual orientation to prenatal factors that act to shape the development of the brain and the expression of sexual behaviours in animals and humans. One major influence discussed relates to organisational effects that the early hormone environment exerts on both gender identity and sexual orientation. Evidence that gender identity and sexual orientation are masculinised by prenatal exposure to testosterone and feminised in it absence is drawn from basic research in animals, correlations of biometric indices of androgen exposure and studies of clinical conditions associated with disorders in sexual development. There are, however, important exceptions to this theory that have yet to be resolved. Family and twin studies indicate that genes play a role, although no specific candidate genes have been identified. Evidence that relates to the number of older brothers implicates maternal immune responses as a contributing factor for male sexual orientation. It remains speculative how these influences might relate to each other and interact with postnatal socialisation. Nonetheless, despite the many challenges to research in this area, existing empirical evidence makes it clear that there is a significant biological contribution to the development of an individual's sexual identity and sexual orientation.

Treatment of Depression in Women

Women are more likely than men to experience depression throughout the life span. Sex differences in neurochemistry and brain structure, as well as societal factors may contribute to women's increased likelihood of depression. Pharmacological research targeting depression has historically excluded women, leading to a knowledge gap regarding effective antidepressant treatment in women. Antidepressant pharmacokinetics and pharmacodynamics are clearly different in men and women, necessitating a thoughtful approach to their prescription and management. Hormone changes associated with the menstrual cycle, pregnancy, and menopause also contribute to differences in depression and effective antidepressant use in women. Finally, it is important to consider potential interactions between antidepressant drugs and medications specifically used by women (oral contraceptives, tamoxifen, and estrogen).

Genomic Characteristics of Gender Dysphoria Patients and Identification of Rare Mutations in RYR3 Gene

Gender dysphoria (GD) is characterized by an incongruence between the gender assigned at birth and the gender with which one identifies. The biological mechanisms of GD are unclear. While common genetic variants are associated with GD, positive findings have not always been replicated. To explore the role of rare variants in GD susceptibility within the Han Chinese population, whole-genome sequencing of 9 Han female-to-male transsexuals (FtMs) and whole-exome sequencing of 4 Han male-to-female transsexuals (MtFs) were analyzed using a pathway burden analysis in which variants are first collapsed at the gene level and then by Gene Ontology terms. Novel nonsynonymous variants in ion transport genes were significantly enriched in FtMs (P- value, 2.41E-10; Fold enrichment, 2.8) and MtFs (P- value, 1.04E-04; Fold enrichment, 2.3). Gene burden analysis comparing 13 GD cases and 100 controls implicated RYR3, with three heterozygous damaging mutations in unrelated FtMs and zero in controls (P = 0.001). Importantly, protein structure modeling of the RYR3 mutations indicated that the R1518H mutation made a large structural change in the RYR3 protein. Overall, our results provide information about the genetic basis of GD.

Deep sequencing reveals variations in somatic cell mosaic mutations between monozygotic twins with discordant psychiatric disease

Monozygotic (MZ) twins have been thought to be genetically identical. However, recent studies have shown discordant variants between them. We performed whole-exome sequencing (WES) in five MZ twin pairs with discordant neurodevelopmental disorders and one healthy control MZ twin to detect discordant variants. We identified three discordant variants confirmed by deep sequencing after analysis by personalized next-generation sequencing (NGS). Three mutations in FBXO38 (chr5:147774428;T>G), SMOC2 (chr6:169051385;A>G) and TDRP (chr8:442616;A>G), were detected with low allele frequency of mutant alleles on deep sequencing, suggesting that these loci are mosaic due to somatic mutations in a developmental stage. Our results suggest that deep sequencing analysis would be an adequate method to detect discordant mutations in candidate genes responsible for heritable diseases.

Gender identity and the management of the transgender patient: a guide for non-specialists

In this review, we introduce the topic of transgender medicine, aimed at the non-specialist clinician working in the UK. Appropriate terminology is provided alongside practical advice on how to appropriately care for transgender people. We offer a brief theoretical discussion on transgenderism and consider how it relates to broader understandings of both gender and disease. In respect to epidemiology, while it is difficult to assess the exact size of the transgender population in the UK, population surveys suggest a prevalence of between 0.2 and 0.6% in adults, with rates of referrals to gender identity clinics in the UK increasing yearly. We outline the legal framework that protects the rights of transgender people, showing that is not legal for physicians to deny transgender people access to services based on their personal beliefs. Being transgender is often, although not always, associated with gender dysphoria, a potentially disabling condition in which the discordance between a person's natal sex (that assigned to them at birth) and gender identity results in distress, with high associated rates of self-harm, suicidality and functional impairment. We show that gender reassignment can be a safe and effective treatment for gender dysphoria with counselling, exogenous hormones and surgery being the mainstay of treatment. The role of the general practitioner in the management of transgender patients is discussed and we consider whether hormone therapy should be initiated in primary care in the absence of specialist advice, as is suggested by recent General Medical Council guidance.

On the Relationship Between Domain-Specific Creative Achievement and Sexual Orientation in Swedish Twins

Despite the commonly held belief that homosexual males and females are more creative compared to heterosexuals, empirical studies on homosexuality and its relationship to creativity have been sparse, often with questionable methodology and very small sample sizes, reporting mixed findings. No study till date has explored the associations described above in a large population-based and genetically informative sample. Here, we examined such potential associations between sexual orientation and creative achievement in several different domains (music, writing, dance, visual arts, science, invention, and theater) using a large cohort of 4494 Swedish twins (of which 7.5 % were not exclusively heterosexual). Data were analyzed for the sexes separately as well as pooled. Results showed significant associations between sexual orientation and two of the creative domains-theater and writing-with non-heterosexuals being more creative in these domains. In all other domains, no significant differences were found between the non-heterosexual and heterosexual groups. Findings from co-twin control analyses suggested that the significant associations may not be causal in nature (i.e., homosexual orientation leads to higher creativity) but due to shared liability. However, we lacked power to differentiate between shared genetic and shared environmental influences. Results and potential implications are discussed critically.

A Review of the Status of Brain Structure Research in Transsexualism

The present review focuses on the brain structure of male-to-female (MtF) and female-to-male (FtM) homosexual transsexuals before and after cross-sex hormone treatment as shown by in vivo neuroimaging techniques. Cortical thickness and diffusion tensor imaging studies suggest that the brain of MtFs presents complex mixtures of masculine, feminine, and demasculinized regions, while FtMs show feminine, masculine, and defeminized regions. Consequently, the specific brain phenotypes proposed for MtFs and FtMs differ from those of both heterosexual males and females. These phenotypes have theoretical implications for brain intersexuality, asymmetry, and body perception in transsexuals as well as for Blanchard's hypothesis on sexual orientation in homosexual MtFs. Falling within the aegis of the neurohormonal theory of sex differences, we hypothesize that cortical differences between homosexual MtFs and FtMs and male and female controls are due to differently timed cortical thinning in different regions for each group. Cross-sex hormone studies have reported marked effects of the treatment on MtF and FtM brains. Their results are used to discuss the early postmortem histological studies of the MtF brain.

Sex differences in the brain–an interplay of sex steroid hormones and sex chromosomes

Although considerable progress has been made in our understanding of brain function, many questions remain unanswered. The ultimate goal of studying the brain is to understand the connection between brain structure and function and behavioural outcomes. Since sex differences in brain morphology were first observed, subsequent studies suggest different functional organization of the male and female brains in humans. Sex and gender have been identified as being a significant factor in understanding human physiology, health and disease, and the biological differences between the sexes is not limited to the gonads and secondary sexual characteristics, but also affects the structure and, more crucially, the function of the brain and other organs. Significant variability in brain structures between individuals, in addition to between the sexes, is factor that complicates the study of sex differences in the brain. In this review, we explore the current understanding of sex differences in the brain, mostly focusing on preclinical animal studies.

Regional volumes and spatial volumetric distribution of gray matter in the gender dysphoric brain

The sexual differentiation of the brain is primarily driven by gonadal hormones during fetal development. Leading theories on the etiology of gender dysphoria (GD) involve deviations herein. To examine whether there are signs of a sex-atypical brain development in GD, we quantified regional neural gray matter (GM) volumes in 55 female-to-male and 38 male-to-female adolescents, 44 boys and 52 girls without GD and applied both univariate and multivariate analyses. In girls, more GM volume was observed in the left superior medial frontal cortex, while boys had more volume in the bilateral superior posterior hemispheres of the cerebellum and the hypothalamus. Regarding the GD groups, at whole-brain level they differed only from individuals sharing their gender identity but not from their natal sex. Accordingly, using multivariate pattern recognition analyses, the GD groups could more accurately be automatically discriminated from individuals sharing their gender identity than those sharing their natal sex based on spatially distributed GM patterns. However, region of interest analyses indicated less GM volume in the right cerebellum and more volume in the medial frontal cortex in female-to-males in comparison to girls without GD, while male-to-females had less volume in the bilateral cerebellum and hypothalamus than natal boys. Deviations from the natal sex within sexually dimorphic structures were also observed in the untreated subsamples. Our findings thus indicate that GM distribution and regional volumes in GD adolescents are largely in accordance with their respective natal sex. However, there are subtle deviations from the natal sex in sexually dimorphic structures, which can represent signs of a partial sex-atypical differentiation of the brain.

Sexual orientation related differences in cortical thickness in male individuals

Previous neuroimaging studies demonstrated sex and also sexual orientation related structural and functional differences in the human brain. Genetic information and effects of sex hormones are assumed to contribute to the male/female differentiation of the brain, and similar effects could play a role in processes influencing human's sexual orientation. However, questions about the origin and development of a person's sexual orientation remain unanswered, and research on sexual orientation related neurobiological characteristics is still very limited. To contribute to a better understanding of the neurobiology of sexual orientation, we used magnetic resonance imaging (MRI) in order to compare regional cortical thickness (Cth) and subcortical volumes of homosexual men (hoM), heterosexual men (heM) and heterosexual women (heW). hoM (and heW) had thinner cortices primarily in visual areas and smaller thalamus volumes than heM, in which hoM and heW did not differ. Our results support previous studies, which suggest cerebral differences between hoM and heM in regions, where sex differences have been reported, which are frequently proposed to underlie biological mechanisms. Thus, our results contribute to a better understanding of the neurobiology of sexual orientation.

Discordant transsexualism in male monozygotic twins: neuroanatomical and psychological differences

One monozygotic male twin pair discordant for transsexualism is described. Both twins were interviewed and tested with the Wechsler Adult Intelligence Scale battery for cognitive functions and they underwent magnetic resonance imaging to measure the volumes of specific cerebral structures. Interviews with the twins and their mother indicated no unusual medical or life history events that could have had a causal role in the emergence of the disorder. Both cognitive function testing and neuroimaging detected differences between the twins that could be related to unexplained epigenetic effects and exogenous hormone usage.

Sexuality and gender role in autism spectrum disorder: a case control study

The ‘extreme male brain theory of autism’ describes an extreme male pattern of cognitive traits defined as strong systemising abilities paired with empathising weaknesses in autism spectrum disorder. However, beyond these cognitive traits, clinical observations have suggested an ambiguous gender-typed pattern regarding several sexually dimorphic traits.

The aim of the present study was to investigate if patterns of non-cognitive sexually dimorphic traits differed between the autism spectrum disorder and control groups. Fifty adults with autism spectrum disorder and intelligence within the normal range, and 53 neurotypical controls responded to questions on gender role, self-perceived gender typicality and gender identity, as well as sexuality. Measures used were a Swedish modification of the Bem Sex Role Inventory and questions on sexuality and gender designed for the purpose of this study. Our results showed that one common gender role emerged in the autism spectrum disorder group. Masculinity (e.g. assertiveness, leadership and competitiveness) was weaker in the autism spectrum disorder group than in the controls, across men and women. Self-perceived gender typicality did not differ between the groups but tomboyism and bisexuality were overrepresented amongst women with autism spectrum disorder. Lower libido was reported amongst both male and female participants with autism spectrum disorder compared with controls. We conclude that the extreme male patterns of cognitive functions in the autistic brain do not seem to extend to gender role and sexuality. A gender-atypical pattern for these types of characteristics is suggested in autism spectrum disorder.

Oxytocin's impact on social face processing is stronger in homosexual than heterosexual men

Oxytocin is an evolutionarily highly preserved neuropeptide that contributes to the regulation of social interactions including the processing of facial stimuli. We hypothesized that its improving effect on social approach behavior depends on perceived sexual features and, consequently, on sexual orientation. In 19 homosexual and 18 heterosexual healthy young men, we investigated the acute effect of intranasal oxytocin (24IU) and placebo, respectively, on the processing of social stimuli as assessed by ratings of trustworthiness, attractiveness and approachability for male and female faces. Faces were each presented with a neutral, a happy, and an angry expression, respectively. In heterosexual subjects, the effect of oxytocin administration was restricted to a decrease in ratings of trustworthiness for angry female faces (p<0.02). In contrast, in homosexual men oxytocin administration robustly increased ratings of attractiveness and approachability for male faces regardless of the facial expression (all p ≤ 0.05), as well as ratings of approachability for happy female faces (p<0.01). Results indicate that homosexual in comparison to heterosexual men display higher sensitivity to oxytocin's enhancing impact on social approach tendencies, suggesting that differences in sexual orientation imply differential oxytocinergic signaling.

Care of the transgender patient: the role of the gynecologist

Gender dysphoria refers to distress that is caused by a sense of incongruity between an individual's self-identified gender and natal sex. Diagnosis is made in accordance with the Diagnostic and Statistical Manual of Mental Disorders and treatment first involves psychiatric therapy, which can help determine a patient's true goals in regards to achieving gender identity. Patients who wish to transition to the opposite sex must undergo a supervised real-life test and often are treated with hormonal therapy to develop physical characteristics consistent with their gender identity. Sex reassignment surgery is an option for patients who wish to transition completely. Transpatients face many barriers when it comes to basic health needs including education, housing, and health care. This is a result of long-standing marginalization and discrimination against this community. Because of these barriers, many patients do not receive the proper health care that they need. Additionally, because of certain high-risk behaviors as well as long-term hormonal therapy, transpatients have different routine health care needs that should be addressed in the primary care setting. Gynecologists play an important role in caring for transgender patients and should be knowledgeable about the general principles of transgender health.

On the quest for a biomechanism of transsexualism: is there a role for BDNF?

Previous studies hypothesized a neurobiological mechanism for gender identity disorder (GID). Recently a possible role for serum brain-derived neurotrophic factor (BDNF) was suggested on the basis of reduced serum BDNF levels in male-to-female individuals. Here we review the question whether there is indeed a role of BDNF in the development of transsexualism.

Androgen receptor function links human sexual dimorphism to DNA methylation

Sex differences are well known to be determinants of development, health and disease. Epigenetic mechanisms are also known to differ between men and women through X-inactivation in females. We hypothesized that epigenetic sex differences may also result from sex hormone functions, in particular from long-lasting androgen programming. We aimed at investigating whether inactivation of the androgen receptor, the key regulator of normal male sex development, is associated with differences of the patterns of DNA methylation marks in genital tissues. To this end, we performed large scale array-based analysis of gene methylation profiles on genomic DNA from labioscrotal skin fibroblasts of 8 males and 26 individuals with androgen insensitivity syndrome (AIS) due to inactivating androgen receptor gene mutations. By this approach we identified differential methylation of 167 CpG loci representing 162 unique human genes. These were significantly enriched for androgen target genes and low CpG content promoter genes. Additional 75 genes showed a significant increase of heterogeneity of methylation in AIS compared to a high homogeneity in normal male controls. Our data show that normal and aberrant androgen receptor function is associated with distinct patterns of DNA-methylation marks in genital tissues. These findings support the concept that transcription factor binding to the DNA has an impact on the shape of the DNA methylome. These data which derived from a rare human model suggest that androgen programming of methylation marks contributes to sexual dimorphism in the human which might have considerable impact on the manifestation of sex-associated phenotypes and diseases.

Cerebral serotonin transporter asymmetry in females, males and male-to-female transsexuals measured by PET in vivo

The serotonergic system modulates brain functions that are considered to underlie affective states, emotion and cognition. Several lines of evidence point towards a strong lateralization of these mental processes, which indicates similar asymmetries in associated neurotransmitter systems. Here, our aim was to investigate a potential asymmetry of the serotonin transporter distribution using positron emission tomography and the radioligand [(11)C]DASB in vivo. As brain asymmetries may differ between sexes, we further aimed to compare serotonin transporter asymmetry between females, males and male-to-female (MtF) transsexuals whose brains are considered to be partly feminized. Voxel-wise analysis of serotonin transporter binding in all groups showed both strong left and rightward asymmetries in several cortical and subcortical structures including temporal and frontal cortices, anterior cingulate, hippocampus, caudate and thalamus. Further, male controls showed a rightward asymmetry in the midcingulate cortex, which was absent in females and MtF transsexuals. The present data support the notion of a lateralized serotonergic system, which is in line with previous findings of asymmetric serotonin-1A receptor distributions, extracellular serotonin concentrations, serotonin turnover and uptake. The absence of serotonin transporter asymmetry in the midcingulate in MtF transsexuals may be attributed to an absence of brain masculinization in this region.

Effects of androgenization on the white matter microstructure of female-to-male transsexuals. A diffusion tensor imaging study

Diffusion tensor imaging (DTI) can sensitively detect white matter sex differences and the effects of pharmacological treatments. Before cross-sex hormone treatment, the white matter microstructure of several brain bundles in female-to-male transsexuals (FtMs) differs from those in females but not from that in males. The purpose of this study was to investigate whether cross-sex hormone treatment (androgenization) affects the brain white matter microstructure. Using a Siemens 3 T Trio Tim Magneton, DTI was performed twice, before and during cross-sex hormonal treatment with testosterone in 15 FtMs scanned. Fractional anisotropy (FA) was analyzed on white matter of the whole brain, and the latter was spatially analyzed using Tract-Based Spatial Statistics. Before each scan the subjects were assessed for serum testosterone, sex hormone binding globulin level (SHBG), and their free testosterone index. After at least seven months of cross-gender hormonal treatment, FA values increased in the right superior longitudinal fasciculus (SLF) and the right corticospinal tract (CST) in FtMs compared to their pre-treatment values. Hierarchical regression analyses showed that the increments in the FA values in the SLF and CST are predicted by the free testosterone index before hormonal treatment. All these observations suggest that testosterone treatment changes white matter microstructure in FtMs.