Subcortical gray matter changes in transgender subjects after long-term cross-sex hormone administration

Increased iron deposition in subcortical nuclear mass in treatment naïve transgender women: An exploratory quantitative susceptibility mapping study

OBJECTIVE

The aim of this study was to investigate altered iron deposition in deep brain regions of transgender women (TW) population using quantitative susceptibility mapping (QSM).

MATERIAL & METHOD

45 TW, 28 cisgender men (CM) and 18 cisgender women (CW) were prospectively recruited. All participants underwent a 3.0T magnetic resonance imaging of the brain. QSM post-processing technique was applied to obtain susceptibility value for regions of the caudate, putamen, internal globus pallidus, external globus pallidus, ventral pallidum, nucleus accumbens, substantia nigra pars compacta, substantia nigra pars reticulata, red nucleus, subthalamic nucleus and dentate nucleus. The analysis of covariance was used to investigate the iron deposition differences between three groups controlling for age and education. The false discovery rate (FDR) was used for multiple comparison correction.

RESULTS

After correcting for FDR, the TW group showed increased susceptibility value in the left internal globus pallidus compared to the CM group. There were no significantly different susceptibility value between the TW and the CW groups after correcting for FDR.

CONCLUSION

The iron deposition in the internal globus pallidus region of TW was higher than that of CM, and there was no significant difference between TW and CW, Further investigation is warranted to gain a more comprehensive understanding of cerebral iron dysregulation in transgender people and its associated physiological mechanisms.

The Potential Health Risks and Benefits of Progesterone in the Transgender Woman Population-A Narrative Review

INTRODUCTION

Currently, progesterone is notably absent from conventional feminizing hormone therapies for transgender women. Anecdotal reports indicate the potential for health advantages following the incorporation of progesterone into treatment regimens. The primarily female hormone, progesterone naturally surges in women during the menstrual luteal phase. When administered exogenously, it may expedite bodily changes that are pivotal for gender transition. Progesterone holds promise as a potential remedy for various health conditions prevalent in the transgender woman population.

METHODS

This narrative review synthesizes existing literature and presents a comprehensive account of the administration of exogenous progesterone in transgender women. A literature search was conducted using the PubMed, Embase, ScienceDirect, and ResearchGate databases. The following keywords were used in the search: progesterone, transgender, breast neoplasms, lactation, prostate, testicular neoplasms, and thrombosis. These terms were combined using Boolean operators. The results of the initial search were screened by three independent reviewers based on their relevance to the topic under study.

RESULTS

A total of 104 studies were initially identified as meeting the criteria for inclusion. Following an assessment based on the contents of the title, abstract, and full text, 39 studies were deemed eligible for inclusion. A critical examination of health outcomes was conducted across key sections, including breast development, mental health, lactation, cancer risk (breast and prostate), thrombosis, and nervous and other systems.

DISCUSSION

The use of progesterone in the transgender woman population is a topic that has yet to be sufficiently researched. The limited sample size, short follow-up periods, and lack of randomization restrict the potential for achieving a robust scientific evidence base. In order to gain a fuller understanding of this topic, findings from studies on contraception, hormone replacement therapy, and animal models were considered.

CONCLUSIONS

Progesterone may have a beneficial effect on the bodies of transgender women without significant adverse health effects. Further investigation through well-designed studies is recommended. Randomized controlled trials that include various dosages, broad and long-term effects, and precise demographics are needed. There is an immediate need for more knowledge to create appropriate patent and clinical practice guidelines.

Menstrual management in transgender and gender diverse individuals: psychiatric and psychosocial considerations

Transgender and gender-diverse (TGD) menstruators are individuals assigned female at birth (AFAB)*, who retain the capacity to menstruate and have a gender identity that differs from their natal sex. Reports indicate up to 1.6 million individuals in the US identify as TGD. Until recently, the mainstream menstrual discourse has failed to capture the experience of transmenstruators. However, a better understanding of the menstrual experiences of TGD-AFAB will allow for more individualized patient-centered care. In this review, we provide the relevant data necessary to inform the psychiatric management of menstruation in TGD-AFAB individuals, including experiences of menstruation, preferences for menstrual management, and the impact on mental health. Our review indicates that menstrual care in TGD patients must be tailored to the individual; clinicians should remain open-minded to the unique experience of transmenstruators; gender-affirming menstrual care is necessary to reduce psychological burden. It should not be assumed that TGD-AFAB menstruators are utilizing appropriate contraceptive methods and should receive contraceptive and fertility preservation counseling. We highlight the importance of having these conversations early in the reproductive arch, even before puberty onset. Keeping in mind the gender minority stress model, in the upcoming sections, we discuss the limited body of literature on mood disorders in TGD-AFAB individuals who menstruate, undergo menstrual suppression, or continue to ovulate. The psychological impact of hormonal therapies is also reviewed.

Imaging phenotypic differences in multiple sclerosis: at the crossroads of aging, sex, race, and ethnicity

Clear sex differences are observed in clinical and imaging phenotypes of multiple sclerosis (MS), which evolve significantly over the age spectrum, and more specifically, during reproductive milestones such as pregnancy and menopause. With neuroimaging being an outcome measure and also a key subclinical biomarker of subsequent clinical phenotype in MS, this comprehensive review aims to provide an overview of sex and hormone differences in structural and functional imaging biomarkers of MS, including lesion burden and location, atrophy, white matter integrity, functional connectivity, and iron distribution. Furthermore, how therapies aimed at altering sex hormones can impact imaging of women and men with MS over the lifespan is discussed. This review also explores the key intersection between age, sex, and race/ethnicity in MS, and how this intersection may affect imaging biomarkers of MS.

Refining Research and Representation of Sexual and Gender Diversity in Neuroscience

There are opportunities to improve neuroscience that include lesbian, gay, bisexual, and transgender (LGBT) people. In this review, we briefly describe how the history of LGBT people in psychiatry has influenced neuroimaging approaches; how these attitudes have shifted over time; and what we can do to ensure that our future work is rigorous, ethical, and in service of the LGBT community. We suggest ways to refine neuroimaging methodologies to improve our understanding of marginalization and stigma while shifting away from research that focuses solely on the "etiology" or origins of LGBT identities. We also offer suggestions for conducting representative research that is LGBT-inclusive, regardless of the population of interest.

Gender-affirming hormonal treatment changes neural processing of emotions in trans men: An fMRI study

BACKGROUND

Some transgender people desire a transition through gender-affirming hormone treatment (GAHT). To date, it is unknown how GAHT changes emotion perception in transgender people.

METHODS

Thirty transgender men (TM), 30 cisgender men (CM), and 35 cisgender women (CW) underwent 3 Tesla functional magnetic resonance imaging (fMRI) while passively viewing emotional faces (happy, angry, surprised faces) at two timepoints (T0 and T1). At T0 all participants were hormone-naïve, while TM immediately commenced testosterone supplementation at T0. The second scanning session (T1) occurred after 6-10 months of GAHT in TM. All 3 groups completed both T0 and T1 RESULTS: GAHT in TM shifted the neural profile whilst processing emotions from a sex-assigned at birth pattern at T0 (similar to CW) to a consistent with gender identity pattern at T1 (similar to CM). Overall, the brain patterns stayed the same for the cis people at T0 and T1.

CONCLUSIONS

These findings document the impact of hormone treatment, and testosterone supplementation specifically, on emotion perception in TM.

Childhood lead exposure and sex-based neurobehavioral functioning in adolescence

It is well documented that childhood lead exposure is associated with long-term decreases in intelligence quotients (IQ). Lesser known is the relationship with neurobehavioral domains, especially in adolescence. This study sought to identify cross-sectional and longitudinal associations between lead exposure and adolescent executive and visual-motor functioning and examine sex-based differences. Participants were 681 children from Jintan, China who had their blood lead levels (BLLs) assessed at age 3-5 years and 12 years old and neurobehavioral functioning assessed through the University of Pennsylvania Computerized Neurocognitive Battery (PennCNB) platform http://www.med.upenn.edu/bbl at 12 years old. Mean BLLs were 6.41 mcg/dl at age 3-5 years and 3.10 mcg/dl at 12. BLLs at 3-5 years and 12 years were used as predictors for the individual neurobehavioral domains in general linear models while controlling for father and mother occupation and education, residence location, age, and adolescent IQ. Models were run separately for males and females. In adjusted models, males BLLs at 3-5 years were associated with increased time to correctly complete tasks in multiple domains including abstraction/flexibility (β = 19.90, 95% CI( 4.26, 35.54) and spatial processing (β = 96.00, 95% CI 6.18, 185.82) at 12 years. For females in adjusted models, BLLs at 3-5 years were associated with increasing time to correctly complete tasks on the episodic memory domain task (β = 34.59, 95% CI 5.33, 63.84) at 12 years. Two adolescent cross-sectional relationships remained in the adjusted models for males only, suggesting a positive association between BLLs and increasing time for correct responses on the attentional domain task (β = 15.08, 95% CI 0.65, 29.51) and decreasing time for correct responses on the episodic memory task (β = -73.49, 95% CI -138.91, -8.06) in males at 12 years. These associations remained with and without controlling for IQ. These results suggest that lead exposure is associated with overall deficits in male and female neurobehavioral functioning, though in different domains and different timing of exposure.

Transwoman Elite Athletes: Their Extra Percentage Relative to Female Physiology

There is increasing debate as to whether transwoman athletes should be included in the elite female competition. Most elite sports are divided into male and female divisions because of the greater athletic performance displayed by males. Without the sex division, females would have little chance of winning because males are faster, stronger, and have greater endurance capacity. Male physiology underpins their better athletic performance including increased muscle mass and strength, stronger bones, different skeletal structure, better adapted cardiorespiratory systems, and early developmental effects on brain networks that wires males to be inherently more competitive and aggressive. Testosterone secreted before birth, postnatally, and then after puberty is the major factor that drives these physiological sex differences, and as adults, testosterone levels are ten to fifteen times higher in males than females. The non-overlapping ranges of testosterone between the sexes has led sports regulators, such as the International Olympic Committee, to use 10 nmol/L testosterone as a sole physiological parameter to divide the male and female sporting divisions. Using testosterone levels as a basis for separating female and male elite athletes is arguably flawed. Male physiology cannot be reformatted by estrogen therapy in transwoman athletes because testosterone has driven permanent effects through early life exposure. This descriptive critical review discusses the inherent male physiological advantages that lead to superior athletic performance and then addresses how estrogen therapy fails to create a female-like physiology in the male. Ultimately, the former male physiology of transwoman athletes provides them with a physiological advantage over the cis-female athlete.

The Impact of Gender-affirming Hormone Therapy on Anatomic Structures of the Brain Among Transgender Individuals

Despite the growing numbers of individuals who identify as transgender, this population continues to face worse mental health outcomes compared with the general population. Transgender individuals attempt suicide at a rate that is almost 9 times that of the general population. Few studies have reported on the positive effect of gender-affirming hormone therapy on mental health outcomes in transgender individuals. It is likely that this effect is due in part to the physiological responses that occur as a result of hormone therapy that mitigate incongruencies between one's gender identity and assigned sex. To our knowledge, only limited studies have shown a connection between gender-affirming hormone therapy, its effect on the brain's structure, and long-term effects that this may have on mental health outcomes. The authors propose that, in addition to the physiological responses that occur as a direct result of hormone therapy and the validation that results from receiving gender-affirming medical care, mental health outcomes in transgender individuals may also improve due to the role that hormone therapy plays in altering the brain's structure, possibly shaping the brain to become more like that of the gender with which an individual identifies. In this article, the authors review the current literature on the effects that gender-affirming hormone therapy has on mental health outcomes and anatomic structures of the brain in transgender individuals.

'That Time of the Month' - Investigating the Influence of the Menstrual Cycle and Oral Contraceptives on the Brain Using Magnetic Resonance Imaging

The stereotypic and oversimplified relationship between female sex hormones and undesirable behavior dates to the earliest days of human society, as already the ancient Greek word for the uterus, "hystera" indicated an aversive connection. Remaining and evolving throughout the centuries, transcending across cultures and various aspects of everyday life, its perception was only recently reframed. Contemporarily, the complex interaction of hormonal phases (i. e., the menstrual cycle), hormonal medication (i. e., oral contraceptives), women's psychological well-being, and behavior is the subject of multifaceted and more reflected discussions. A driving force of this ongoing paradigm shift was the introduction of this highly interesting and important topic into the realm of scientific research. This refers to neuroscientific research as it enables a multimodal approach combining aspects of physiology, medicine, and psychology. Here a growing body of literature points towards significant alterations of both brain function, such as lateralization of cognitive functions, and structure, such as gray matter concentrations, due to fluctuations and changes in hormonal levels. This especially concerns female sex hormones. However, the more research is conducted within this field, the less reliable these observations and derived insights appear. This may be due to two particular factors: measurement inconsistencies and diverse hormonal phases accompanied by interindividual differences. The first factor refers to the prominent unreliability of one of the primarily utilized neuroscientific research instruments: functional magnetic resonance imaging (fMRI). This unreliability is seemingly present in paradigms and analyses, and their interplay, and is additionally affected by the second factor. In more detail, hormonal phases and levels further influence neuroscientific results obtained through fMRI as outcomes vary drastically across different cycle phases and medication. This resulting vast uncertainty thus tremendously hinders the further advancement of our understanding of how female sex hormones might alter brain structure and function and, ultimately, behavior.This review summarizes parts of the current state of research and outlines the essential requirements to further investigate and understand the female brain's underlying physiological and anatomical features.

Effects of sex hormones on brain GABA and glutamate levels in a cis- and transgender cohort

Sex hormones affect the GABAergic and glutamatergic neurotransmitter system as demonstrated in animal studies. However, human research has mostly been correlational in nature. Here, we aimed at substantiating causal interpretations of the interaction between sex hormones and neurotransmitter function by using magnetic resonance spectroscopy imaging (MRSI) to study the effect of gender-affirming hormone treatment (GHT) in transgender individuals. Fifteen trans men (TM) with a DSM-5 diagnosis of gender dysphoria, undergoing GHT, and 15 age-matched cisgender women (CW), receiving no therapy, underwent MRSI before and after at least 12 weeks. Additionally, sex differences in neurotransmitter levels were evaluated in an independent sample of 80 cisgender men and 79 cisgender women. Mean GABA+ (combination of GABA and macromolecules) and Glx (combination of glutamate and glutamine) ratios to total creatine (GABA+/tCr, Glx/tCr) were calculated in five predefined regions-of-interest (hippocampus, insula, pallidum, putamen and thalamus). Linear mixed models analysis revealed a significant measurement by gender identity effect (pcorr. = 0.048) for GABA+/tCr ratios in the hippocampus, with the TM cohort showing decreased GABA+/tCr levels after GHT compared to CW. Moreover, analysis of covariance showed a significant sex difference in insula GABA+/tCr ratios (pcorr. = 0.049), indicating elevated GABA levels in cisgender women compared to cisgender men. Our study demonstrates GHT treatment-induced GABA+/tCr reductions in the hippocampus, indicating hormone receptor activation on GABAergic cells and testosterone-induced neuroplastic processes within the hippocampus. Moreover, elevated GABA levels in the female compared to the male insula highlight the importance of including sex as factor in future MRS studies. DATA AVAILABILITY STATEMENT: Due to data protection laws processed data is available from the authors upon reasonable request. Please contact rupert.lanzenberger@meduniwien.ac.at with any questions or requests.

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.

The Effects of Testosterone on the Brain of Transgender Men

Transgender men (TM) experience an incongruence between the female sex assigned when they were born and their self-perceived male identity. Some TM seek for a gender affirming hormone treatment (GAHT) to induce a somatic transition from female to male through continuous administration of testosterone. GAHT seems to be relatively safe. However, testosterone produces structural changes in the brain as detected by quantitative magnetic resonance imaging. Mainly, it induces an increase in cortical volume and thickness and subcortical structural volume probably due to the anabolic effects. Animal models, specifically developed to test the anabolic hypothesis, suggest that testosterone and estradiol, its aromatized metabolite, participate in the control of astrocyte water trafficking, thereby controlling brain volume.

High-dose testosterone treatment reduces monoamine oxidase A levels in the human brain: A preliminary report

The sex hormones testosterone and estradiol influence brain structure and function and are implicated in the pathogenesis, prevalence and disease course of major depression. Recent research employing gender-affirming hormone treatment (GHT) of gender dysphoric individuals and utilizing positron emission tomography (PET) indicates increased serotonin transporter binding upon high-dosages of testosterone treatment. Here, we investigated the effects of GHT on levels of monoamine oxidase A (MAO-A), another key target of antidepressant treatment. Participants underwent PET with the radioligand [11C]harmine to assess cerebral MAO-A distribution volumes (VT) before and four months after initiation of GHT. By the time this study was terminated for technical reasons, 18 transgender individuals undergoing GHT (11 transmen, TM and 7 transwomen, TW) and 17 cis-gender subjects had been assessed. Preliminary analysis of available data revealed statistically significant MAO-A VT reductions in TM under testosterone treatment in six of twelve a priori defined regions of interest (middle frontal cortex (-10%), anterior cingulate cortex (-9%), medial cingulate cortex (-10.5%), insula (-8%), amygdala (-9%) and hippocampus (-8.5%, all p<0.05)). MAO-A VT did not change in TW receiving estrogen treatment. Despite the limited sample size, pronounced MAO-A VT reduction could be observed, pointing towards a potential effect of testosterone. Considering MAO-A's central role in regulation of serotonergic neurotransmission, changes to MAO-A VT should be further investigated as a possible mechanism by which testosterone mediates risk for, symptomatology of, and treatment response in affective disorders.

Comparison and Reliability of Hippocampal Subfield Segmentations Within FreeSurfer Utilizing T1- and T2-Weighted Multispectral MRI Data

The accurate segmentation of in vivo magnetic resonance imaging (MRI) data is a crucial prerequisite for the reliable assessment of disease progression, patient stratification or the establishment of putative imaging biomarkers. This is especially important for the hippocampal formation, a brain area involved in memory formation and often affected by neurodegenerative or psychiatric diseases. FreeSurfer, a widely used automated segmentation software, offers hippocampal subfield delineation with multiple input options. While a single T1-weighted (T1) sequence is regularly used by most studies, it is also possible and advised to use a high-resolution T2-weighted (T2H) sequence or multispectral information. In this investigation it was determined whether there are differences in volume estimations depending on the input images and which combination of these deliver the most reliable results in each hippocampal subfield. 41 healthy participants (age = 25.2 years ± 4.2 SD) underwent two structural MRIs at three Tesla (time between scans: 23 days ± 11 SD) using three different structural MRI sequences, to test five different input configurations (T1, T2, T2H, T1 and T2, and T1 and T2H). We compared the different processing pipelines in a cross-sectional manner and assessed reliability using test-retest variability (%TRV) and the dice coefficient. Our analyses showed pronounced significant differences and large effect sizes between the processing pipelines in several subfields, such as the molecular layer (head), CA1 (head), hippocampal fissure, CA3 (head and body), fimbria and CA4 (head). The longitudinal analysis revealed that T1 and multispectral analysis (T1 and T2H) showed overall higher reliability across all subfields than T2H alone. However, the specific subfields had a substantial influence on the performance of segmentation results, regardless of the processing pipeline. Although T1 showed good test-retest metrics, results must be interpreted with caution, as a standard T1 sequence relies heavily on prior information of the atlas and does not take the actual fine structures of the hippocampus into account. For the most accurate segmentation, we advise the use of multispectral information by using a combination of T1 and high-resolution T2-weighted sequences or a T2 high-resolution sequence alone.

Leveraging high-resolution 7-tesla MRI to derive quantitative metrics for the trigeminal nerve and subnuclei of limbic structures in trigeminal neuralgia

BACKGROUND

Trigeminal Neuralgia (TN) is a chronic neurological disease that is strongly associated with neurovascular compression (NVC) of the trigeminal nerve near its root entry zone. The trigeminal nerve at the site of NVC has been extensively studied but limbic structures that are potentially involved in TN have not been adequately characterized. Specifically, the hippocampus is a stress-sensitive region which may be structurally impacted by chronic TN pain. As the center of the emotion-related network, the amygdala is closely related to stress regulation and may be associated with TN pain as well. The thalamus, which is involved in the trigeminal sensory pathway and nociception, may play a role in pain processing of TN. The objective of this study was to assess structural alterations in the trigeminal nerve and subregions of the hippocampus, amygdala, and thalamus in TN patients using ultra-high field MRI and examine quantitative differences in these structures compared with healthy controls.

METHODS

Thirteen TN patients and 13 matched controls were scanned at 7-Tesla MRI with high resolution, T1-weighted imaging. Nerve cross sectional area (CSA) was measured and an automated algorithm was used to segment hippocampal, amygdaloid, and thalamic subregions. Nerve CSA and limbic structure subnuclei volumes were compared between TN patients and controls.

RESULTS

CSA of the posterior cisternal nerve on the symptomatic side was smaller in patients (3.75 mm2) compared with side-matched controls (5.77 mm2, p = 0.006). In TN patients, basal subnucleus amygdala volume (0.347 mm3) was reduced on the symptomatic side compared with controls (0.401 mm3, p = 0.025) and the paralaminar subnucleus volume (0.04 mm3) was also reduced on the symptomatic side compared with controls (0.05 mm3, p = 0.009). The central lateral thalamic subnucleus was larger in TN patients on both the symptomatic side (0.033 mm3) and asymptomatic side (0.035 mm3), compared with the corresponding sides in controls (0.025 mm3 on both sides, p = 0.048 and p = 0.003 respectively). The inferior and lateral pulvinar thalamic subnuclei were both reduced in TN patients on the symptomatic side (0.2 mm3 and 0.17 mm3 respectively) compared to controls (0.23 mm3, p = 0.04 and 0.18 mm3, p = 0.04 respectively). No significant findings were found in the hippocampal subfields analyzed.

CONCLUSIONS

These findings, generated through a highly sensitive 7 T MRI protocol, provide compelling support for the theory that TN neurobiology is a complex amalgamation of local structural changes within the trigeminal nerve and structural alterations in subnuclei of limbic structures directly and indirectly involved in nociception and pain processing.

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).

The Neuroanatomy of Transgender Identity: Mega-Analytic Findings From the ENIGMA Transgender Persons Working Group

BACKGROUND

In contrast to cisgender persons, transgender persons identify with a different gender than the one assigned at birth. Although research on the underlying neurobiology of transgender persons has been accumulating over the years, neuroimaging studies in this relatively rare population are often based on very small samples resulting in discrepant findings.

AIM

To examine the neurobiology of transgender persons in a large sample.

METHODS

Using a mega-analytic approach, structural MRI data of 803 non-hormonally treated transgender men (TM, n = 214, female assigned at birth with male gender identity), transgender women (TW, n = 172, male assigned at birth with female gender identity), cisgender men (CM, n = 221, male assigned at birth with male gender identity) and cisgender women (CW, n = 196, female assigned at birth with female gender identity) were analyzed.

OUTCOMES

Structural brain measures, including grey matter volume, cortical surface area, and cortical thickness.

RESULTS

Transgender persons differed significantly from cisgender persons with respect to (sub)cortical brain volumes and surface area, but not cortical thickness. Contrasting the 4 groups (TM, TW, CM, and CW), we observed a variety of patterns that not only depended on the direction of gender identity (towards male or towards female) but also on the brain measure as well as the brain region examined.

CLINICAL TRANSLATION

The outcomes of this large-scale study may provide a normative framework that may become useful in clinical studies.

STRENGTHS AND LIMITATIONS

While this is the largest study of MRI data in transgender persons to date, the analyses conducted were governed (and restricted) by the type of data collected across all participating sites.

CONCLUSION

Rather than being merely shifted towards either end of the male-female spectrum, transgender persons seem to present with their own unique brain phenotype. Mueller SC, Guillamon A, Zubiaurre-Elorza L, et al. The Neuroanatomy of Transgender Identity: Mega-Analytic Findings From the ENIGMA Transgender Persons Working Group. J Sex Med 2021;18:1122-1129.

Neuroimaging gender dysphoria: a novel psychobiological model

Gender identity development is complex and involves several key processes. Transgender people experience incongruence between their biological and identified gender. This incongruence can cause significant impairment in overall functioning and lead to gender dysphoria (GD). The pathophysiology of GD is complex and is poorly understood. A PubMed search based on predetermined eligibility criteria was conducted to review neuropsychiatric articles focused on neurological, biological and neuroimaging aspects of gender development, transgender identity and GD. The information obtained from the literature was then used to formulize a GD model. Distinct gray matter volume and brain activation and connectivity differences were found in individuals with GD compared to controls, suggesting a neurobiological basis of GD; which leads to the concept of brain gender. Individuals with GD encounter a recurrent conflict between their brain gender and the societal feedback; which causes recurrent and ongoing cognitive dissonance, finally leading to GD and functional connectivity and activation changes in the transgender brain. GD has neurobiological basis, but it is closely associated with the individuals' interaction with the external world, their self-perception and the feedback received in return. We propose a novel model where the development of GD includes cognitive dissonance, involving anterior cingulate cortex and ventral striatum as the key brain structures. This model can be used to generate testable hypotheses using behavioral and neuroimaging techniques to understand the neuropsychobiology of GD.

The influence of microsatellite polymorphisms in sex steroid receptor genes ESR1, ESR2 and AR on sex differences in brain structure

The androgen receptor (AR), oestrogen receptor alpha (ESR1) and oestrogen receptor beta (ESR2) play essential roles in mediating the effect of sex hormones on sex differences in the brain. Using Voxel-based morphometry (VBM) and gene sizing in two independent samples (discovery n ​= ​173, replication ​= ​61), we determine the common and unique influences on brain sex differences in grey (GM) and white matter (WM) volume between repeat lengths (n) of microsatellite polymorphisms AR(CAG)n, ESR1(TA)n and ESR2(CA)n. In the hypothalamus, temporal lobes, anterior cingulate cortex, posterior insula and prefrontal cortex, we find increased GM volume with increasing AR(CAG)n across sexes, decreasing ESR1(TA)n across sexes and decreasing ESR2(CA)n in females. Uniquely, AR(CAG)n was positively associated with dorsolateral prefrontal and orbitofrontal GM volume and the anterior corona radiata, left superior fronto-occipital fasciculus, thalamus and internal capsule WM volume. ESR1(TA)n was negatively associated with the left superior corona radiata, left cingulum and left inferior longitudinal fasciculus WM volume uniquely. ESR2(CA)n was negatively associated with right fusiform and posterior cingulate cortex uniquely. We thus describe the neuroanatomical correlates of three microsatellite polymorphisms of steroid hormone receptors and their relationship to sex differences.

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Microsatellite polymorphisms in sex hormone receptor genes influence volume in regions of brain sex difference

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AR(CAG)n repeat length is positively associated with grey and white matter volume across males and females

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ESR1(TA)n repeat length is negatively associated with grey and white matter volume across males and females

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ESR2(CA)n repeat length is negatively associated with grey matter volume in females but not in males

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Repeat length was associated with volume in the hypothalamus, insula, temporal cortices, prefrontal cortices, inferior and superior longitudinal fasciculi in the three genes.

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These regions were largely replicated in an independent cohort acquired on a separate scanner.

Progesterone - Friend or foe?

Estradiol is the "prototypic" sex hormone of women. Yet, women have another sex hormone, which is often disregarded: Progesterone. The goal of this article is to provide a comprehensive review on progesterone, and its metabolite allopregnanolone, emphasizing three key areas: biological properties, main functions, and effects on mood in women. Recent years of intensive research on progesterone and allopregnanolone have paved the way for new treatment of postpartum depression. However, treatment for premenstrual syndrome and premenstrual dysphoric disorder as well as contraception that women can use without risking mental health problems are still needed. As far as progesterone is concerned, we might be dealing with a two-edged sword: while its metabolite allopregnanolone has been proven useful for treatment of PPD, it may trigger negative symptoms in women with PMS and PMDD. Overall, our current knowledge on the beneficial and harmful effects of progesterone is limited and further research is imperative.

Effects of adult male rat feminization treatments on brain morphology and metabolomic profile

Body feminization, as part of gender affirmation process of transgender women, decreases the volume of their cortical and subcortical brain structures. In this work, we implement a rat model of adult male feminization which reproduces the results in the human brain and allows for the longitudinal investigation of the underlying structural and metabolic determinants in the brain of adult male rats undergoing feminization treatments. Structural MRI and Diffusion Tensor Imaging (DTI) were used to non-invasively monitor in vivo cortical brain volume and white matter microstructure over 30 days in adult male rats receiving estradiol (E₂), estradiol plus cyproterone acetate (CA), an androgen receptor blocker and antigonadotropic agent (E₂ + CA), or vehicle (control). Ex vivo cerebral metabolic profiles were assessed by ¹H High Resolution Magic Angle Spinning NMR (¹H HRMAS) at the end of the treatments in samples from brain regions dissected after focused microwave fixation (5 kW). We found that; a) Groups receiving E₂ and E₂ + CA showed a generalized bilateral decrease in cortical volume; b) the E₂ + CA and, to a lesser extent, the E₂ groups maintained fractional anisotropy values over the experiment while these values decreased in the control group; c) E₂ treatment produced increases in the relative concentration of brain metabolites, including glutamate and glutamine and d) the glutamine relative concentration and fractional anisotropy were negatively correlated with total cortical volume. These results reveal, for the first time to our knowledge, that the volumetric decreases observed in trans women under cross-sex hormone treatment can be reproduced in a rat model. Estrogens are more potent drivers of brain changes in male rats than anti-androgen treatment.

Biological sex classification with structural MRI data shows increased misclassification in transgender women

Transgender individuals (TIs) show brain-structural alterations that differ from their biological sex as well as their perceived gender. To substantiate evidence that the brain structure of TIs differs from male and female, we use a combined multivariate and univariate approach. Gray matter segments resulting from voxel-based morphometry preprocessing of N = 1753 cisgender (CG) healthy participants were used to train (N = 1402) and validate (20% holdout N = 351) a support-vector machine classifying the biological sex. As a second validation, we classified N = 1104 patients with depression. A third validation was performed using the matched CG sample of the transgender women (TW) application sample. Subsequently, the classifier was applied to N = 26 TW. Finally, we compared brain volumes of CG-men, women, and TW-pre/post treatment cross-sex hormone treatment (CHT) in a univariate analysis controlling for sexual orientation, age, and total brain volume. The application of our biological sex classifier to the transgender sample resulted in a significantly lower true positive rate (TPR-male = 56.0%). The TPR did not differ between CG-individuals with (TPR-male = 86.9%) and without depression (TPR-male = 88.5%). The univariate analysis of the transgender application-sample revealed that TW-pre/post treatment show brain-structural differences from CG-women and CG-men in the putamen and insula, as well as the whole-brain analysis. Our results support the hypothesis that brain structure in TW differs from brain structure of their biological sex (male) as well as their perceived gender (female). This finding substantiates evidence that TIs show specific brain-structural alterations leading to a different pattern of brain structure than CG-individuals.

What happens when we forget our own narrative: Transgender dementia case study

OBJECTIVE

Neuropsychological evaluations in a geriatric population have an assortment of challenges due to increased risk in the population for chronic/acute medical conditions, varied psychiatric disorders, and chronic negative lifestyle behaviors, all which impact one's cognitive functioning. One relatively new challenge is conducting cognitive evaluations within an elderly transgender population. There is a considerable lack of specific normative data in neuropsychological evaluations for transgender individuals due to the prevalence of binary gender categorization in current scoring protocols. However, a reasonable question is whether gender is such a significant normative factor, as the field of neuropsychology once thought?

METHOD

The current article reports on these issues in the context of a case of an 85-year-old transgender female who was referred to an outpatient neuropsychology service due to cognitive and functional declines.

RESULTS

Her performance on the neuropsychological evaluation indicated significant decline across many of the cognitive domains measured. When using binary male and female normative data, scores did not statistically differ across the majority of the domains.

CONCLUSIONS

Overall, it was difficult to determine nuanced gender differences due to the patient's marked cognitive impairment. Potentially, differences may be more obvious in a less impaired individual.

Gender-affirming hormone treatment - A unique approach to study the effects of sex hormones on brain structure and function

Investigating the effects of the gender-affirming hormone treatment of transgender people using neuroimaging provides a unique opportunity to study the impact of high dosages of sex hormones on human brain structure and function. This line of research is of relevance from a basic neuroscientific as well as from a psychiatric viewpoint. Prevalence rates, etiopathology, and disease course of many psychiatric disorders exhibit sex differences which are linked to differences in sex hormone levels. Here, we review recent neuroimaging studies from others and our group that investigate the effects of gender-affirming hormone treatment in a longitudinal design utilizing structural and functional magnetic resonance imaging and positron emission tomography. Studies point to a general anabolic and anticatabolic effect of testosterone on grey and white matter structure, whereas estradiol and antiandrogen treatment seems to have partly opposite effects. Moreover, preliminary research indicates that gender-affirming hormone treatment influences serotonergic neurotransmission, a finding that is especially interesting for psychiatry. A clear picture of a hormonal influence on brain activity has yet to emerge. In conclusion, the available evidence reviewed here clearly indicates that sex hormone applications influence brain structure and function in the adult human brain.

The Link between Estradiol and Neuroplasticity in Transgender Women after Gender-Affirming Surgery: A Bimodal Hypothesis

For transgender individuals, gender-affirming surgery (GAS) and cross-sex hormone therapy (CSHT) are part of the gender transition process. Scientific evidence supporting the maintenance of CSHT after GAS-related gonadectomy is accumulating. However, few data are available on the impact of CSHT on the brain structure following hypogonadism. Thus, we aimed to investigate links between estradiol and brain cortical thickness (CTh) and cognition in 18 post-gonadectomy transgender women using a longitudinal design. For this purpose, the participants underwent a voluntary period of CSHT washout of at least 30 days, followed by estradiol re-institution for 60 days. High-resolution T1-weighted brain images, hormonal measures, working and verbal memory were collected at 2 time points: on the last day of the washout (t1) and on the last day of the 2-month CSHT period (t2). Between these 2 time points, CTh increased within the left precentral gyrus and right precuneus but decreased within the right lateral occipital cortex. However, these findings did not survive corrections of multiple comparisons. Nevertheless, there was a significant negative correlation between changes in estradiol levels and changes in CTh. This effect was evident in the left superior frontal gyrus, the left middle temporal gyrus, the right precuneus, the right superior temporal gyrus, and the right pars opercularis. Although there was an improvement in verbal memory following hypogonadism correction, we did not observe a significant relationship between changes in memory scores and CTh. Altogether, these findings suggest that there is a link between estradiol and CTh.

Probing the Impact of Gender-Affirming Hormone Treatment on Odor Perception

Evidence suggests that women outperform men in core aspects of odor perception, and sex hormones may play a significant role in moderating this effect. The gender-affirming treatment (GAT) of transgender persons constitutes a powerful natural experiment to study the psychological and behavioral effects of high dosages of cross-sex hormone applications. Therefore, our aim was to investigate the effects of GAT on odor perception in a sample of 131 participants including female and male controls, as well as transmen and transwomen over their first 4 months of gender transition. The Sniffin’ Sticks test battery was used to measure odor detection, discrimination, and identification at baseline, as well as 1 and 4 months after the start of GAT. Plasma levels of estradiol, testosterone, and sex hormone-binding globulin were analyzed for each assessment point. Results revealed no significant change of olfactory performance in the two transgender groups compared with female and male controls. There was no significant difference between groups at baseline or any other time point. Neither biological sex, nor gender identity had an influence on odor perception. Moreover, there was no significant correlation between sex hormones and odor perception and between GAT-induced changes in sex hormones and changes in odor perception. Our results indicate that the effects of sex hormones on olfactory performance are subtle, if present at all. However, our results do not preclude hormonal effects on odors not included in the Sniffin’ Sticks test battery, such as body odors or odors associated with sex.

Neurobiological mechanisms underlying sex-related differences in stress-related disorders: Effects of neuroactive steroids on the hippocampus

Men and women differ in their vulnerability to a variety of stress-related illnesses, but the underlying neurobiological mechanisms are not well understood. This is likely due to a comparative dearth of neurobiological studies that assess male and female rodents at the same time, while human neuroimaging studies often don't model sex as a variable of interest. These sex differences are often attributed to the actions of sex hormones, i.e. estrogens, progestogens and androgens. In this review, we summarize the results on sex hormone actions in the hippocampus and seek to bridge the gap between animal models and findings in humans. However, while effects of sex hormones on the hippocampus are largely consistent in animals and humans, methodological differences challenge the comparability of animal and human studies on stress effects. We summarise our current understanding of the neurobiological mechanisms that underlie sex-related differences in behavior and discuss implications for stress-related illnesses.

Health considerations for transgender women and remaining unknowns: a narrative review

Transgender (trans) women (TW) were assigned male at birth but have a female gender identity or gender expression. The literature on management and health outcomes of TW has grown recently with more publication of research. This has coincided with increasing awareness of gender diversity as communities around the world identify and address health disparities among trans people. In this narrative review, we aim to comprehensively summarize health considerations for TW and identify TW-related research areas that will provide answers to remaining unknowns surrounding TW's health. We cover up-to-date information on: (1) feminizing gender-affirming hormone therapy (GAHT); (2) benefits associated with GAHT, particularly quality of life, mental health, breast development and bone health; (3) potential risks associated with GAHT, including cardiovascular disease and infertility; and (4) other health considerations like HIV/AIDS, breast cancer, other tumours, voice therapy, dermatology, the brain and cognition, and aging. Although equally deserving of mention, feminizing gender-affirming surgery, paediatric and adolescent populations, and gender nonbinary individuals are beyond the scope of this review. While much of the data we discuss come from Europe, the creation of a United States transgender cohort has already contributed important retrospective data that are also summarized here. Much remains to be determined regarding health considerations for TW. Patients and providers will benefit from larger and longer prospective studies involving TW, particularly regarding the effects of aging, race and ethnicity, type of hormonal treatment (e.g. different oestrogens, anti-androgens) and routes of administration (e.g. oral, parenteral, transdermal) on all the topics we address.

Polygenic risk for circulating reproductive hormone levels and their influence on hippocampal volume and depression susceptibility

Altered reproductive hormone levels have been associated with the pathophysiology of depressive disorders and this risk may be imparted by their modulatory effect upon hippocampal structure and function. Currently it is unclear whether altered levels of reproductive hormones are causally associated with hippocampal volume reductions and the risk of depressive disorders. Here, we utilize genome-wide association study (GWAS) summary statistics from a GWAS focusing on reproductive hormones, consisting of 2913 individuals. Using this data, we generated polygenic risk scores (PRS) for estradiol, progesterone, prolactin and testosterone in the European RADIANT cohort consisting of 176 postpartum depression (PPD) cases (100% female, mean age: 41.6 years old), 2772 major depressive disorder (MDD) cases (68.6% female, mean age: 46.9 years old) and 1588 control participants (62.5% female, mean age: 42.4 years old), for which there was also a neuroimaging subset of 111 individuals (60.4% female, mean age: 50.0 years old). Only the best-fit PRS for estradiol showed a significant negative association with hippocampal volume, as well as many of its individual subfields; including the molecular layer and granule cell layer of the dentate gyrus, subiculum, CA1, CA2/3 and CA4 regions. Interestingly, several of these subfields are implicated in adult hippocampal neurogenesis. When we tested the same estradiol PRS for association with case-control status for PPD or MDD there was no significant relationship observed. Here, we provide evidence that genetic risk for higher plasma estradiol is negatively associated with hippocampal volume, but this does not translate into an increased risk of MDD or PPD. This work suggests that the relationship between reproductive hormones, the hippocampus, and depression is complex, and that there may not be a clear-cut pathway for etiology or risk moderation.

Gender-affirming hormones and surgery in transgender children and adolescents

The Endocrine Society Clinical Practice Guidelines on the treatment of gender incongruent people recommend the use of gender-affirming cross-sex hormone (CSH) interventions in transgender children and adolescents who request this treatment, who have undergone psychiatric assessment, and have maintained a persistent transgender identity. The intervention can help to affirm gender identity by inducing masculine or feminine physical characteristics that are congruent with an individual's gender expression, while aiming to improve mental health and quality-of-life outcomes. Some transgender individuals might also wish to access gender-affirming surgeries during adolescence; however, research to inform best clinical practice for surgeons and other medical professionals is scarce. This Review explores the available published evidence on gender-affirming CSH and surgical interventions in transgender children and adolescents, amalgamating findings on mental health outcomes, cognitive and physical effects, side-effects, and safety variables. The small amount of available data suggest that when clearly indicated in accordance with international guidelines, gender-affirming CSHs and chest wall masculinisation in transgender males are associated with improvements in mental health and quality of life. Evidence regarding surgical vaginoplasty in transgender females younger than age 18 years remains extremely scarce and conclusions cannot yet be drawn regarding its risks and benefits in this age group. Further research on an international scale is urgently warranted to clarify long-term outcomes on psychological functioning and safety.

Cross sex hormone treatment is linked with a reversal of cerebral patterns associated with gender dysphoria to the baseline of cisgender controls

Transgender persons experience incongruence between their gender identity and birth-assigned sex. The resulting gender dysphoria (GD), is frequently treated with cross-sex hormones. However, very little is known about how this treatment affects the brain of individuals with GD, nor do we know the neurobiology of GD. We recently suggested that disconnection of fronto-parietal networks involved in own-body self-referential processing could be a plausible mechanism, and that the anatomical correlate could be a thickening of the mesial prefrontal and precuneus cortex, which is unrelated to sex. Here, we investigate how cross-sex hormone treatment affects cerebral tissue in persons with GD, and how potential changes are related to self-body perception. Longitudinal MRI measurements of cortical thickness (Cth) were carried out in 40 transgender men (TrM), 24 transgender women (TrW) and 19 controls. Cth increased in the mesial temporal and insular cortices with testosterone treatment in TrM, whereas anti-androgen and oestrogen treatment in TrW caused widespread cortical thinning. However, after correction for treatment-related changes in total grey and white matter volumes (increase with testosterone; decrease with anti-androgen and oestrogen), significant Cth decreases were observed in the mesial prefrontal and parietal cortices, in both TrM and TrW (vs. controls) - regions showing greater pre-treatment Cth than in controls. The own body - self congruence ratings increased with treatment, and correlated with a left parietal cortical thinning. These data confirm our hypothesis that GD may be associated with specific anatomical features in own-body/self-processing circuits that reverse to the pattern of cisgender controls after cross-sex hormone treatment.

What has sex got to do with it? The role of hormones in the transgender brain

Sex differences and hormonal effects in presumed cisgender individuals have been well-studied and support the concept of a mosaic of both male and female "characteristics" in any given brain. Gonadal steroid increases and fluctuations during peri-puberty and across the reproductive lifespan influence the brain structure and function programmed by testosterone and estradiol exposures in utero. While it is becoming increasingly common for transgender and gender non-binary individuals to block their transition to puberty and/or use gender-affirming hormone therapy (GAHT) to obtain their desired gender phenotype, little is known about the impact of these manipulations on brain structure and function. Using sex differences and the effects of reproductive hormones in cisgender individuals as the backdrop, we summarize here the existing nascent neuroimaging and behavioral literature focusing on potential brain and cognitive differences in transgender individuals at baseline and after GAHT. Research in this area has the potential to inform our understanding of the developmental origins of gender identity and sex difference in response to gonadal steroid manipulations, but care is needed in our research questions and methods to not further stigmatize sex and gender minorities.

Prediction of Autopsy Verified Neuropathological Change of Alzheimer's Disease Using Machine Learning and MRI

Background: Alzheimer’s disease (AD) is the most common form of dementia. While neuropathological changes pathognomonic for AD have been defined, early detection of AD prior to cognitive impairment in the clinical setting is still lacking. Pioneer studies applying machine learning to magnetic-resonance imaging (MRI) data to predict mild cognitive impairment (MCI) or AD have yielded high accuracies, however, an algorithm predicting neuropathological change is still lacking. The objective of this study was to compute a prediction model supporting a more distinct diagnostic criterium for AD compared to clinical presentation, allowing identification of hallmark changes even before symptoms occur.

Methods: Autopsy verified neuropathological changes attributed to AD, as described by a combined score for Aβ-peptides, neurofibrillary tangles and neuritic plaques issued by the National Institute on Aging – Alzheimer’s Association (NIAA), the ABC score for AD, were predicted from structural MRI data with RandomForest (RF). MRI scans were performed at least 2 years prior to death. All subjects derive from the prospective Vienna Trans-Danube Aging (VITA) study that targeted all 1750 inhabitants of the age of 75 in the starting year of 2000 in two districts of Vienna and included irregular follow-ups until death, irrespective of clinical symptoms or diagnoses. For 68 subjects MRI as well as neuropathological data were available and 49 subjects (mean age at death: 82.8 ± 2.9, 29 female) with sufficient MRI data quality were enrolled for further statistical analysis using nested cross-validation (CV). The decoding data of the inner loop was used for variable selection and parameter optimization with a fivefold CV design, the new data of the outer loop was used for model validation with optimal settings in a fivefold CV design. The whole procedure was performed ten times and average accuracies with standard deviations were reported.

Results: The most informative ROIs included caudal and rostral anterior cingulate gyrus, entorhinal, fusiform and insular cortex and the subcortical ROIs anterior corpus callosum and the left vessel, a ROI comprising lacunar alterations in inferior putamen and pallidum. The resulting prediction models achieved an average accuracy for a three leveled NIAA AD score of 0.62 within the decoding sets and of 0.61 for validation sets. Higher accuracies of 0.77 for both sets, respectively, were achieved when predicting presence or absence of neuropathological change.

Conclusion: Computer-aided prediction of neuropathological change according to the categorical NIAA score in AD, that currently can only be assessed post-mortem, may facilitate a more distinct and definite categorization of AD dementia. Reliable detection of neuropathological hallmarks of AD would enable risk stratification at an earlier level than prediction of MCI or clinical AD symptoms and advance precision medicine in neuropsychiatry.

Conducting neuropsychological assessment with transgender individuals

OBJECTIVE

The purpose of this paper is to provide an overview of helpful clinical practices when working with transgender adult individuals.

METHOD

While the number of openly transgender individuals appears to be growing with society's increased acceptance and awareness, many neuropsychologists have had few opportunities to gain experience with this patient population. In this article, we review the existing literature as it relates to clinical neuropsychological practice.

RESULTS

We describe important terminology, ideals for creating an environment of respect, and how existing clinical guidelines for transgender individuals may apply to neuropsychology. In addition, we review the primary steps in the assessment process and provide a set of principles and recommendations for conducting neuropsychological assessments with transgender patients.

CONCLUSIONS

There is a paucity of guidance in the field for working with transgender individuals. This article represents a step forward in the dialog and we look forward to future research that develops appropriate normative information, increases understanding of psychosocial factors, and better appreciates the range of hormonal influences for transgender individuals.

Gender-Affirming Hormone Use in Transgender Individuals: Impact on Behavioral Health and Cognition

PURPOSE OF REVIEW

With increasing numbers of transgender and gender non-binary individuals presenting for care, knowing how to elucidate the mental health and cognitive outcomes of gender-affirming hormone therapy (GAHT) is necessary. This article reviews the present literature covering GAHT effects on mood, behavioral health, and cognition in these individuals and offers research priorities to address knowledge gaps.

RECENT FINDINGS

Although there are some conflicting data, GAHT overwhelmingly seems to have positive psychological effects in both adolescents and adults. Research tends to support that GAHT reduces symptoms of anxiety and depression, lowers perceived and social distress, and improves quality of life and self-esteem in both male-to-female and female-to-male transgender individuals. Clinically, prescribing GAHT can help with gender dysphoria-related mental distress. Thus, timely hormonal intervention represents a crucial tool for improving behavioral wellness in transgender individuals, though effects on cognitive processes fundamental for daily living are unknown. Future research should prioritize better understanding of how GAHT may affect executive functioning.

Sex-Dependent Effects of Developmental Lead Exposure on the Brain

The role of sex as an effect modifier of developmental lead (Pb) exposure has until recently received little attention. Lead exposure in early life can affect brain development with persisting influences on cognitive and behavioral functioning, as well as, elevated risks for developing a variety of diseases and disorders in later life. Although both sexes are affected by Pb exposure, the incidence, manifestation, and severity of outcomes appears to differ in males and females. Results from epidemiologic and animal studies indicate significant effect modification by sex, however, the results are not consistent across studies. Unfortunately, only a limited number of human epidemiological studies have included both sexes in independent outcome analyses limiting our ability to draw definitive conclusions regarding sex-differentiated outcomes. Additionally, due to various methodological differences across studies, there is still not a good mechanistic understanding of the molecular effects of lead on the brain and the factors that influence differential responses to Pb based on sex. In this review, focused on prenatal and postnatal Pb exposures in humans and animal models, we discuss current literature supporting sex differences in outcomes in response to Pb exposure and explore some of the ideas regarding potential molecular mechanisms that may contribute to sex-related differences in outcomes from developmental Pb exposure. The sex-dependent variability in outcomes from developmental Pb exposure may arise from a combination of complex factors, including, but not limited to, intrinsic sex-specific molecular/genetic mechanisms and external risk factors including sex-specific responses to environmental stressors which may act through shared epigenetic pathways to influence the genome and behavioral output.

Grey and white matter volumes either in treatment-naïve or hormone-treated transgender women: a voxel-based morphometry study

Many previous magnetic resonance imaging (MRI) studies have documented sex differences in brain morphology, but the patterns of sexual brain differences in transgender women - male sex assigned at birth - with a diagnosis of gender dysphoria (TW) have been rarely investigated to date. We acquired T1-weighted MRI data for the following four (n = 80) groups: treatment-naïve TW (TNTW), TW treated with cross-sex hormones for at least one year (TTW), cisgender men, and cisgender women (cisgender individuals as controls). Differences in whole-brain and regional white matter volume and grey matter volume (GMV) were assessed using voxel-based morphometry. We found lower global brain volumes and regional GMVs in a large portion of the posterior-superior frontal cortex in the cisgender women group than in the TTW and cisgender men groups. Additionally, both transgender groups exhibited lower bilateral insular GMVs than the cisgender women group. Our results highlight differences in the insula in both transgender groups; such differences may be characteristic of TW. Furthermore, these alterations in the insula could be related to the neural network of body perception and reflect the distress that accompanies gender dysphoria.