Context: Transgenders are highly disadvantaged people, deprived of adequate opportunities of earning a respectable living. The forensic literature has emphasized on two genders, male and female, the existence of a third gender (Transgenders) is almost negligible in the literature, and this makes it compulsive to determine their identity through forensic approaches at the time of disasters. Previous studies have demonstrated that no two palatal rugae pattern are alike in their configuration and this unique feature has led us to undertake a study to establish individual identities using palatal rugae pattern.

Aims: The purpose of this study was to compare the palatal rugae pattern among male, female, and transgender population of the Bhopal city.

Settings and Design: This study was cross sectional in nature and conducted on a convenience sample of 148 subjects selected from Bhopal city, Madhya Pradesh. The study involved 49 males, 51 females, and 48 eunuchs in the age range of 17 to 35 years.

Materials and Methods: Maxillary impression using alginate impression material was made and the cast was prepared using die stone on palatal area and dental stone as a base. The palatal rugae pattern was assessed on the basis of number, length, shape, direction, and unification.

Statistical Analysis Used: One way ANOVA was used for comparing the mean values between different genders. The multiple pairwise comparisons were done with the Bonferroni post hoc correction. The statistical significance was fixed at 0.05.

Results: The statistically significant difference with regard to some parameters like number of rugae, fragmentary rugae, wavy rugae, curve rugae, forwardly directed, and backwardly directed rugae between transgender and other gender groups were present.

Conclusion: The difference in the parameters of the palatal rugae pattern among the transgender population and the other gender group is attributed to be the genetic makeup and sexual dimorphism.

Author/-s:       Eshani Saxena; B. R. Chandrashekhar; Sudheer Hongal; Nilesh Torwane; Pankaj Goel; Priyesh Mishra

Publication:     Journal of Forensic Dental Sciences

Web link:          http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4430573/

PS: I’m not sure about the quality of this study; in addition, the studied population was “eunuchs”, who are presumably not identical to male-to-female transsexuals. This group might consist of homosexual males, people with a disorder of sexual development and transsexuals.

Objective: To review current literature that supports a biologic basis of gender identity.

Methods: A traditional literature review.

Results: Evidence that there is a biologic basis for gender identity primarily involves (1) data on gender identity in patients with disorders of sex development (DSDs, also known as differences of sex development) along with (2) neuroanatomical differences associated with gender identity.

Conclusions: Although the mechanisms remain to be determined, there is strong support in the literature for a biologic basis of gender identity.

Author/-s:       Aruna Saraswat; Jamie D. Weinand; Joshua D. Safer

Publication:     Endocrine Practice, 2015

Web link:          http://www.ncbi.nlm.nih.gov/pubmed/25667367

This study was reported in some media articles, such as http://dailyfreepress.com/2015/02/18/bu-researchers-find-biological-basis-for-transgender-identity/.

This study examined whether boys with Gender Identity Disorder (GID) produced less prototypically male speech than control boys without GID, a possibility that has been suggested by clinical observations. Two groups of listeners participated in tasks where they rated the gender typicality of single words (group 1) or sentences (group 2) produced by 15 5–13 year old boys with GID and 15 age-matched boys without GID. Detailed acoustic analyses of the stimuli were also conducted. Boys with GID were rated as less boy-like than boys without GID. In the experiment using sentence stimuli, these group differences were larger than in the experiment using single-word stimuli. Listeners’ ratings were predicted by a variety of acoustic parameters, including ones that differ between the two groups and ones that are stereotypically associated with adult men’s and women’s speech. Future research should examine how these variants are acquired.

Author/-s:       Benjamin Munson; Laura Crocker; Janet B. Pierrehumbert; Allison Owen-Anderson; Kenneth J. Zucker

Publication:     Journal of the Acoustical Society of America, 2015

Web link:          http://faculty.wcas.northwestern.edu/~jbp/publications/Munson_etal_2015.pdf

Click-evoked otoacoustic emissions (CEOAEs) are echo-like sounds that are produced by the inner ear in response to click-stimuli. CEOAEs generally have a higher amplitude in women compared to men and neonates already show a similar sex difference in CEOAEs. Weaker responses in males are proposed to originate from elevated levels of testosterone during perinatal sexual differentiation. Therefore, CEOAEs may be used as a retrospective indicator of someone’s perinatal androgen environment. Individuals diagnosed with Gender Identity Disorder (GID), according to DSM-IV-TR, are characterized by a strong identification with the other gender and discomfort about their natal sex. Although the etiology of GID is far from established, it is hypothesized that atypical levels of sex steroids during a critical period of sexual differentiation of the brain might play a role. In the present study, we compared CEOAEs in treatment-naïve children and adolescents with early-onset GID (24 natal boys, 23 natal girls) and control subjects (65 boys, 62 girls). We replicated the sex difference in CEOAE response amplitude in the control group. This sex difference, however, was not present in the GID groups. Boys with GID showed stronger, more female-typical CEOAEs whereas girls with GID did not differ in emission strength compared to control girls. Based on the assumption that CEOAE amplitude can be seen as an index of relative androgen exposure, our results provide some evidence for the idea that boys with GID may have been exposed to lower amounts of androgen during early development in comparison to control boys.

Author/-s:       Sarah M. Burke; Willeke M. Menks; Peggy T. Cohen-Kettenis; Daniel T. Klink; Julie Bakker

Publication:     Archives of Sexual Behavior, 2014

Web link:          http://link.springer.com/article/10.1007/s10508-014-0278-2

Polycystic ovary syndrome (PCOS) is a heterogeneous group of disorders characterized by ovulation disorder, hyperandrogenism, and polycystic ovarian morphology (PCOM). Several diagnostic criteria suggest that hyperandrogenism is a core symptom of PCOS. Androgens are believed to cause preantral follicle growth and arrest the growth of antral follicles. This results in accumulation of small antral follicles in the ovaries, thus forming PCOM. Observational studies of patients with female-to-male transsexualism or congenital adrenal hyperplasia indicate that androgen administration to these patients does not produce typical PCOS-like features. However, endogenous androgen exposure in early life may lead to some traits of PCOS in adulthood. To reveal the association between the timing of excess androgen exposure and reproductive function, various animal models have been investigated using androgen administration. Rhesus monkeys exposed to excess androgen during the early fetal period show a PCOS-like phenotype, including metabolic and hypothalamic-pituitary characteristics. This finding implies that exposure to excess androgen during this critical period programs the hypothalamic-pituitary-ovary axis and metabolic organs. Although findings obtained in animal studies will not necessarily be replicated in humans, prenatal androgen excess is the dominant PCOS hypothesis.

Author/-s:       Tsuyoshi Baba; Toshiaki Endo; Sayaka Adachi; Keiko Ikeda; Ayumi Shimizu; Miyuki Morishita; Yoshika Kuno; Hiroyuki Honnma; Tamotsu Kiya; Tsuyoshi Saito

Publication:     Journal of Mammalian Ova Research, 2014

Web link:          http://www.bioone.org/doi/abs/10.1274/jmor.31.23

Abstract: Atypical prenatal hormone exposure could be a factor in the development of transsexualism. There is evidence that the 2nd and 4th digit ratio (2D : 4D) associates negatively with prenatal testosterone and positively with estrogens. The aim was to assess the difference in 2D : 4D between female to male transsexuals (FMT) and male to female transsexuals (MFT) and controls. We examined 42 MFT, 38 FMT, and 45 control males and 48 control females. Precise measurements were made by X-rays at the ventral surface of both hands from the basal crease of the digit to the tip using vernier calliper. Control male and female patients had larger 2D : 4D of the right hand when compared to the left hand. Control male’s left hand ratio was lower than in control female’s left hand. There was no difference in 2D : 4D between MFT and control males. MFT showed similar 2D : 4D of the right hand with control women indicating possible influencing factor in embryogenesis and consequently finger length changes. FMT showed the lowest 2D : 4D of the left hand when compared to the control males and females. Results of our study go in favour of the biological aetiology of transsexualism.

Conclusion: Transsexualism in humans is biological in origin. Our findings support a biological etiology of MFT implicating decreased prenatal androgen exposure in MFT. 2D:4D could be potentially used as a marker for prenatal androgen exposure.

Author/-s:       Svetlana Vujović; Srdjan Popović; Ljiljana Mrvošević Marojević; Miomira Ivović; Milina Tančić-Gajić; Miloš Stojanović; Ljiljana V. Marina; Marija Barać; Branko Barać; Milena Kovačević; Dragana Duišin; Jasmina Barišić; Miroslav L. Djordjević; Dragan Micić

Publication:     The Scientific World Journal, 2014

Web link:          http://www.hindawi.com/journals/tswj/aip/763563/

[…] Specifically, we examine the development of gendered speech production in boys aged five to 13 years who vary in their gender expression and gender identity. We compare boys with a clinical label of Gender Identity Disorder (GID) to age-matched boys without GID from the same dialect region. […]In this study, we compared 15 boys with a clinical label of GID with 15 age-matched peers without that label. The individuals ranged in age from five to 13 years old. Participants were recorded producing single words and sentences. These were analyzed acoustically. A subset of approximately 14 words and 14 sentences were used as the stimuli in an experiment in which naïve adults rated the gender typicality of the boys' speech. Separate perception stimuli were conducted for perception of the single word stimuli (n=20 listeners) and the sentence stimuli (n=17 listeners). The inclusion of words as stimuli allowed us to assess whether judgments were linked to the pronunciation of specific vowels and consonants. The inclusion of sentence stimuli allowed us to examine whether distinctive phonetic variants in boys with GID were in more global, sentence-level prosodic features, like patterns of tempo and fundamental frequency. The results of the acoustic analyses found some interesting segmental differences between the groups: boys with GID produced vowels with a higher F2 frequency than did boys without GID, a finding that mirrors differences found between GLB and heterosexual adult men. However, boys with GID produced /s/ with a more diffuse spectrum (suggesting a more dental articulation) than did boys without GID. The latter finding runs contrary to previous work on adults, but is consistent with social stereotypes about adult gay men's speech. None of the global measures of pitch or tempo of the sentences differed between the groups. Two groups of listeners participated in tasks where they rated the gender typicality of single words (group 1) or sentences (group 2) produced by the 30 talkers. Across both experiments, boys with GID were rated as less boy-like than boys without GID. In the experiment using sentence stimuli, these group differences were larger for the 8-13 year-old boys than for the 5-7 year-olds. This finding suggests that these speech styles are gradually learned over the age range we examined. Listeners' ratings were predicted by a variety of acoustic parameters, including ones that authentically differ between boys with and without GID, and ones that are stereotypically associated with less masculine sounding speech in North America. […]

Author/-s:       Benjamin Munson

Publication:     Book of abstracts of LSCD 2014, The 1st Workshop on Late Stages in Speech and Communication Development held at University College London (UCL), London, 2014

Web link:          https://www.ucl.ac.uk/psychlangsci/research/speech/clear-speech-strategies/Publications/book_of_abstracts_LCD2014.pdf

Objective: Cross-sex hormonal therapy and sex reassignment surgery (including gonadectomy) in transsexual persons has an impact on body composition and bone mass and size. However, it is not clear whether baseline differences in bone and body composition between transsexual persons and controls before cross-sex hormonal therapy play a role.

Design: A cross-sectional study with 25 male-to-female transsexual persons (transsexual women) before cross-gender sex steroid exposure (median age 30 years) in comparison with 25 age-matched control men and a male reference population of 941 men.

Main outcome measures: Areal and volumetric bone parameters using respectively dual energy X-ray absorptiometry (DXA) and peripheral quantitative computed tomography (pQCT), body composition (DXA), grip strength (hand dynamometer), Baecke physical activity questionnaire, serum testosterone and 25-OH vitamin D.

Results: Transsexual women before cross-sex hormonal therapy presented with less muscle mass (p ≤ 0.001) and strength (p ≤ 0.05) and a higher prevalence of osteoporosis (16 %) with a lower aBMD at the hip, femoral neck, total body (all p < 0.001) and lumbar spine (p=0.064) compared with control men. A thinner radial cortex (p ≤ 0.01) and lower cortical area at the radius and tibia (both p<0.05) was found in transsexual women vs. control men. Serum testosterone was comparable in all 3 groups, but 25-OH vitamin D was lower in transsexual women (p ≤ 0.001).

Conclusions: Transsexual women before the start of hormonal therapy appear to have lower muscle mass and strength and lower bone mass compared with control men. These baseline differences in bone mass might be related to a less active lifestyle.

Author/-s:       Eva van Caenegem; Y. Taes; Katrien Wierckx; S. Vandewalle; Kaatje Toye; Jean-Marc Kaufman; Thomas Schreiner; Ira R. Haraldsen; Guy T’Sjoen

Publication:     Bone, 2013

Web link:          http://www.ncbi.nlm.nih.gov/pubmed/23369987

The objective of the study was to evaluate the metric features of pelvises of 24 female-to-male (FtM) transsexuals as compared to control groups of 24 healthy males and 24 healthy females. The participants had their pelvises X-rayed with the same X-ray apparatus and in the same position. Seventeen measurements were taken on the basis of X-ray pictures of FtM transsexuals’ pelvises and both comparison groups. Additionally, their body height was compared. The results showed that FtM transsexuals having female body height represent an intermediate size of three pelvic features and male values of five variables. In order to develop a model based on metric variables of the pelvis that would best discriminate the FtM transsexuals, the control females, and the control males, a discriminant analysis was applied. The model included four variables out of 17 metric features: the height of the pubic symphysis, the greatest pelvic breadth, the interischial distance, and the acetabular diameter. The model was found to be the best in discriminating males from females and FtM transsexuals, but considerably less effective in discriminating transsexuals from the two control groups. The results demonstrate that a number of FtM transsexuals’ pelvic measurements reveal “masculinization”, which confirms current results demonstrating a shift in the somatometric traits of transsexual females towards male traits. A discriminant analysis based only on pelvic metric features shows some differences between the size of the pelvis and chromosomal sex in FtM transsexuals, which might indicate a biological basis for gender identity disorder.

Author/-s:       A. Sitek; M. Fijałkowska; E. Żądzińska; B. Antoszewski

Publication:     Archives of Sexual Behavior, 2012

Web link:          http://www.ncbi.nlm.nih.gov/pubmed/22810992

Introduction: Gender identity and the second-to-fourth finger length ratio (2D : 4D) are discriminative between the sexes. However, the relationship between 2D : 4D and gender identity disorder (GID) is still controversial.

Aim: The aim of this study is to investigate the relationship between 2D : 4D and score on the Gender Identity Scale (GIS) in female-to-male (FtM) GID subjects.

Methods: Thirty-seven GID-FtM with testosterone replacement therapy from our clinic were included in this study. As controls, 20 male and 20 female volunteers participated from our institution (medical doctors and nurses). We photocopied left and right hands of the participants and measured the second and fourth finger lengths. Gender identity was measured with the GIS.

Main outcome measures: 2D : 4D digit ratio and GIS in male, female, and GID-FtM subjects.

Results: The 2D : 4D (mean ± standard deviation) in male, female, and GID-FtM were 0.945 ± 0.029, 0.999 ± 0.035, and 0.955 ± 0.029 in right hand and 0.941 ± 0.024, 0.979 ± 0.040, and 0.954 ± 0.036 in left hand, respectively. The 2D : 4D was significantly lower in male controls in both hands and GID-FtM in the right hand than in female controls (P < 0.05, analysis of variance). Multiple linear regression analysis revealed that "consistent gender identity" score in the higher domain in GIS and "persistent gender identity" score in the lower domain are statistically significant variables correlating with 2D : 4D in the right hands among biological females.

Conclusions: The finger length ratio 2D : 4D in GID-FtM was significantly lower than in female controls in the right hand in this study. 2D : 4D showed a positive correlation with GIS score. Because 2D : 4D influences are assumed to be established in early life and to reflect testosterone exposure, our results suggest a relationship between GID-FtM and perinatal testosterone.

Author/-s:       S. Hisasue; S. Sasaki; T. Tsukamoto; S. Horie

Publication:     The Journal of Sexual Medicine, 2012

Web link:          http://www.ncbi.nlm.nih.gov/pubmed/22738413

The aim of this thesis is examine biological and psychosocial factors that contribute to the development of gender-variant or gender-typical identities. Blanchard’s autogynephilia theory (Blanchard, 1989b) suggests that these factors are different in birth-assigned males with different sexual orientations. Previous research has found that genetics, prenatal hormone exposure, neuroanatomy, handedness, dermatoglyphics, fraternal birth order, and abuse are related to gender identity. While a number of investigators have studied these variables individually, this is the first known study to have examined the inter-relationships of these variables in one sample and to include participants with a wide range of gender identities. Data were collected from a convenience sample of 2 277 online-recruited participants with gender-variant and gender-typical identities using an online questionnaire. Participants were mainly white/Caucasian (92 %) adults living in the USA (54 %) and New Zealand (19 %). From the results, reported family concordance for gender-variance and a systematic review of case reports of twins with gender-variant identities indicated genetic determinants of gender identities. Finger-length ratio, systemising, and a systematic review of case reports of gender identity outcomes for adults with intersex and related conditions indicated prenatal hormone determinants of gender identities. Further evidence for biological factors came from elevated levels of non-right handedness among birth assigned females with gender-variant identities. Structural equation modelling showed that the positive relationship between abuse experience and degree of adult gender variance was partially mediated by recalled childhood gender-variance. This suggests abuse may be a cause as well as a result of gender-variance. Contrary to Blanchard’s theory, there were no differences in biological and psychosocial factors between birth-assigned male participants of different sexual orientations. This was the first research to find evidence that biological and psychosocial factors are the same for transsexuals as for persons with other gender-variant identities. Overall, these findings add support for a biological predisposition for gender-variant and gender-typical identities. Psychosocial determinants are likely to be complex and work in interaction with biological factors.

Author/-s:       Jaimie F. Veale

Publication:     Doctoral thesis, Massey University, Albany, New Zealand, 2011

Web link:          http://www.jaimieveale.com/wp-content/uploads/2012/09/PhD-thesis.pdf

This article reviews research on biological and psychosocial factors relevant to the etiology of gender-variant identities. There is evidence for a genetic component of gender-variant identities through studies of twins and other within-family concordance and through studies of specific genes. Evidence that prenatal androgens play a role comes from studies that have examined finger length ratios (2D:4D), prevalence of polycystic ovary syndrome among female-to-male transsexuals, and individuals with intersex and related conditions who are more likely to have reassigned genders. There is also evidence that transsexuals have parts of their brain structure that is typical of the opposite birth-assigned gender. A greater likelihood of non-right-handedness suggests developmental instability may also contribute as a biological factor. There is a greater tendency for persons with gender-variant identities to report childhood abuse and a poor or absent relationship with parents. It is unclear if this is a cause or effect of a gender-variant identity. Parental encouragement of gender-variance is more common among individuals who later develop a gender-variant identity. We conclude that biological factors, especially prenatal androgen levels, play a role in the development of a gender-variant identity and it is likely that psychosocial variables play a role in interaction with these factors.

Author/-s:       Jaimie F. Veale; David E. Clarke; Terri C. Lomax

Publication:     Personality and Individual Differences, 2010

Web link:          http://www.sciencedirect.com/science/article/pii/S0191886909004620

This study examined biological and psychosocial variables that are relevant to the etiology of gender-variance. Data were collected over the internet from 2277 participants of either gender who identified as transsexual, other gender-variant, and not gender-variant. We found number of gender-variant relatives, handedness, emotional abuse, finger length ratios (2D:4D), and systematizing significantly predicted Adult Gender-Variance among participants of both genders. Adult Gender-Variance was also predicted by number of older brothers among birth-assigned males. No significant differences were found in extreme right-handedness or mental rotation. No significant interaction effects were found with sexual orientation. While these findings are generally consistent with past research, there were limitations of the internet-based methodology, including a non-representative sample.

Author/-s:       Jaimie F. Veale; David E. Clarke; Terri C. Lomax

Publication:     Personality and Individual Differences, 2010

Web link:          http://www.sciencedirect.com/science/article/pii/S0191886910001790

This study investigated the functional brain organization of 68 male-to-female (MtF) transwomen and 26 female-to-male (FtM) transmen by comparing their performance with 36 typical male and 28 typical female controls on two indicators of cerebral lateralization: dichotic listening and handedness. A sex-differentiating dichotic test and a handedness questionnaire were administered. It was hypothesized that the MtF participants’ dichotic performance would be significantly different from the control males and resemble the control female pattern. This hypothesis was supported. It was also hypothesized that the FtM dichotic pattern would be significantly different from the control females and would resemble the control male pattern. This hypothesis was not supported. Finally, it was hypothesized that there would be significantly more nonexclusive right-handers in both trans-groups. This hypothesis was supported. Taken together, the dichotic and handedness data reported here indicate that the MtF and FtM conditions are not mirror images in terms of the verbal-auditory aspects of their brain organization and neurobiology plays an important role, particularly in the development of the male-to-female trans-condition.

Author/-s:       Ernest Govier; Milton Diamond; Teresa Wolowiec; Catherine Slade

Publication:     International Journal of Transgenderism, 2010

Web link:          http://www.tandfonline.com/doi/full/10.1080/15532739.2010.514219#.UsfcNU2A2oA

From early childhood, gender identity and the 2nd to 4th finger length ratio (2D:4D) are discriminative characteristics between sexes. Both the human brain and 2D:4D may be influenced by prenatal testosterone levels. This calls for an examination of 2D:4D in patients with gender identity disorder (GID) to study the possible influence of prenatal testosterone on gender identity. Until now, the only study carried out on this issue suggests lower prenatal testosterone levels in right-handed male-to-female GID patients (MtF). We compared 2D:4D of 56 GID patients (39 MtF; 17 female-to-male GID patients, FtM) with data from a control sample of 176 men and 190 women. Bivariate group comparisons showed that right hand 2D:4D in MtF was significantly higher (feminized) than in male controls, but similar to female controls. The comparison of 2D:4D ratios of biological women revealed significantly higher (feminized) values for right hands of right handed FtM. Analysis of variance confirmed significant effects for sex and for gender identity on 2D:4D ratios but not for sexual orientation or for the interaction among variables. Our results indirectly point to the possibility of a weak influence of reduced prenatal testosterone as an etiological factor in the multifactorially influenced development of MtF GID. The development of FtM GID seems even more unlikely to be notably influenced by prenatal testosterone.

Author/-s:       Bernd Kraemer; Thomas Noll; Aba Delsignore; Gabriella Milos; Ulrich Schnyder; Urs Hepp

Publication:     Archives of Sexual Behavior, 2009

Web link:          http://europepmc.org/abstract/MED/17906922

Bone health is a parameter of interest in the daily follow-up of male-to-female (M --> F) transsexual persons both before and after sex reassignment surgery (SRS) due to an intensely changing hormonal milieu. We have studied body composition, areal, geometric, and volumetric bone parameters, using DXA and peripheral quantitative computed tomography at different sites in 50 M --> F transsexual persons, at least 3 years after the start of the hormonal treatment and 1 year after SRS. In this cross-sectional study, hormone levels and markers of bone metabolism were assessed using immunoassays. Prevalence of low bone mass as defined by a Z-score < or = −2.0 according to DXA criteria was 26 % at lumbar spine and 2 % at the total hip. We found no major differences in hormonal parameters between participants with a Z-score < or = or > −2.0. Markers of bone turnover were comparable between subjects with or without low bone mass, indicating a stable bone turnover at the time of investigation. No significant differences in bone size or density were observed between patients on transdermal vs. oral estrogens. Low bone mass is not uncommon in M --> F transsexual persons. Smaller bone size, and a strikingly lower muscle mass compared with men appear to underlie these findings.

Author/-s:       Guy T’Sjoen; Steven Weyers; Youri Taes; Bruno Lapauw; Kaatje Toye; S. Goemaere; Jean-Marc Kaufman

Publication:    Journal of Clinical Densitometry, 2009

Web link:         http://www.sciencedirect.com/science/article/pii/S1094695008005015

The aim of the study was to evaluate the odontometric characteristics of female-to-male transsexuals (FtM) in comparison to control groups of males and females. A total of 48 FtM, aged 20–28 years, were studied. For each tooth, two standard measurements were taken: the mesiodistal (MD) and the buccolingual (BL) diameter of the crown. Significant differences between males and females were found in BL measures of all maxillary teeth as well as mandibular lateral incisor and canine. Within the MD measures, the most distinguishing were maxillary and mandibular canines and the first molars. For seven teeth, there were a total of 14 comparisons of MD (half for the maxilla and half for the mandible) between the control men and women. Of these, the men had larger diameters for 12, of which four were statistically significant. There were also a total of 14 comparisons of BL diameter; of these, the men had larger diameters for 13, of which nine were statistically significant. For seven teeth, there were a total of 14 comparisons of MD between the control men and the FtM. Of these, the men had larger diameters for 12, of which seven were statistically significant. There were also 14 comparisons of BL; of these, the men had larger diameters for 10, of which six were statistically significant. For seven teeth, there were a total of 14 comparisons of MD between the control women and the FtM. Of these, the women had larger diameters for nine, of which three were statistically significant. There were also a total of 14 comparisons of BL; of these, the FtM had larger diameters for 13, of which five were statistically significant. Our study revealed that the shift of values of metric features in teeth of FtM towards males was more frequent in the more sexually dimorphic BL diameters characterized by significantly greater width of the crown of five teeth: maxillary canine, first and second molars, as well as mandibular incisors. The results showed intermediate status of female-to-male transsexuals' teeth between the males and females, which may suggest a genetic basis of transsexualism.

Author/-s:       Bogusław Antoszewski; Elisabeth Zadzińska; Jerzy Foczpański

Publication:     Archives of Sexual Behavior, 2009

Web link:          http://www.ncbi.nlm.nih.gov/pubmed/18274888

Previous research suggests that prenatal testosterone affects the 2D:4D finger ratio in humans, and it has been speculated that prenatal testosterone also affects gender identity differentiation. If both things are true, then one would expect to find an association between the 2D:4D ratio and gender identity. We measured 2D:4D in two samples of patients with gender identity disorder (GID). In Study 1, we compared the 2D:4D ratios of 96 adult male and 51 female patients with GID to that of 90 heterosexual male and 112 heterosexual female controls. In Study 2, we compared the 2D:4D ratios of 67 boys and 34 girls with GID to that of 74 control boys and 72 control girls. In the sample of adults with GID, we classified their sexual orientation as either homosexual or non-homosexual (in relation to their birth sex) to examine whether or not there were any within-group differences as a function of sexual orientation. In the sample of adult men with GID (both homosexual and non-homosexual) and children with GID, we found no evidence of an altered 2D:4D ratio relative to same-sex controls. However, women with GID had a significantly more masculinized ratio compared to the control women. This last finding was consistent with the prediction that a variance in prenatal hormone exposure contributes to a departure from a sex-typical gender identity in women.

Author/-s:       Madeleine S. Wallien; Kenneth J. Zucker; Thomas Dirk Steensma; Peggy T. Cohen-Kettenis

Publication:     Hormones and Behavior, 2008

Web link:          http://www.ncbi.nlm.nih.gov/pubmed/18585715

The studies described in this thesis cover four main themes. First, we addressed the assessment of gender identity disorder (GID)/gender dysphoria. Second, we examined three potential determinants of GID in childhood. Third, we investigated the (social) consequences of having a GID in childhood. Fourth, we studied the long-term psychosexual outcome of gender-referred children.

Psychometric research: In chapter 2 we reported on a cross-national, cross-clinic comparative analysis of an instrument, called the Gender Identity Interview for Children (GIIC). The GIIC was administered to 376 gender-referred children from a gender identity clinic in Toronto, Canada, 228 gender-referred children from our own clinic, and 180 control children from Toronto (M age: 7.65 yrs). Factor analysis identified a strong one-factor solution that contained all 12 items on the GIIC, accounting for 32.4% of the total variance. Probands from both clinics had a significantly higher deviant score than the controls, with effect sizes of d = 1.72 for the Canadian probands and d =2.98 for the Dutch probands. The Dutch probands had significantly higher deviant scores than the Canadian gender probands. As expected, probands in both clinics who met complete DSM criteria for GID had a significantly higher deviant score than probands sub-threshold for the diagnosis. Using cutoff scores of 3+ or 4+ deviant responses yielded specificity rates of 86.1% and 92.8%, respectively, for the controls. Sensitivity rates were higher for the Dutch probands than for the Toronto probands. This study was the first to report on the discriminant validity of the GIIC in a sample of children outside of North America.

Chapter 3 reported on results of a cross-national, cross-clinic comparative analysis of a quantitative and standardized parent-report measure of gender identity and gender role behavior named the Gender Identity Questionnaire for Children (GIQC). Data of 338 gender-referred children from Toronto were compared with data of 156 gender-referred children from Utrecht/Amsterdam (the Utrecht clinic was transferred to Amsterdam in 2002). First of all, the probands from both clinics had higher cross-gender scores than the controls, providing evidence for the validity of the instrument. The percentages of children in the two clinics who met complete DSM criteria of GID were comparable. There were also differences between the clinics. The gender-referred boys from Utrecht/Amsterdam had a significantly lower total score (indicating more cross-gender behavior) than the gender-referred boys from Toronto, but there was no significant difference for girls. In the Toronto sample, the gender-referred girls had a significantly higher total score than the gender-referred boys, but there was no significant sex difference in the Utrecht/Amsterdam sample. Across both clinics, the GIQC total score was significantly lower for the gender-referred children who met the complete DSM criteria for GID, than the gender-referred children who were sub-threshold for GID (Cohen's d = 1.08). This result provides evidence for the validity of the GID diagnosis and is the first to demonstrate this in a cross-national, cross-clinic comparative context. The results also provide some support for cross-clinic consistency in clinician-based diagnosis of GID.

Potential determinants of GID: In chapter 4 we reported on a study assessing anxiety and stress in 25 children with GID and 25 control children by measuring their cortisol, heart rate (HR) and skin conductance levels (SCL), and asking them to report their moods and experience of control. By using an established psychological challenge involving provocation and frustration, we investigated whether children with GID as compared to controls without GID reacted in a more anxious way. The gender dysphoric children reported more negative emotions than the controls and had a tonically elevated SCL. There were no differences between the groups in cortisol and HR. This study lends some support to the idea that children with GID have a more anxious nature as compared to controls.

Chapter 5 concerns the prevalence and type of co-morbidity in gender dysphoric children, examined with the Diagnostic Interview Schedule for Children-Parent version (DISC-P). We assessed psychopathology according to the DSM in two groups of children. The first group consisted of 120 Dutch children (age range: 4–11) who were referred to our Gender Identity Clinic (GID group), and the second group consisted of 47 Dutch children who were referred to an ADHD clinic (ADHD group). We found that 52% of the children diagnosed with GID had one or more diagnoses other than GID. As expected, more internalizing (37%) than externalizing (23%) psychopathology was present in both boys and girls. Furthermore, the odds of having internalizing or externalizing co-morbidity were higher in the clinical comparison group (ADHD group) than in the GID group (odds ratios were 1.28 and 1.39, respectively). Finally, 31% of the children with GID suffered from an anxiety disorder. From the results of this categorical diagnostic study we concluded that children with GID are at risk for developing co-occurring problems, that internalizing disorders were not indicative for children with GID, and that, as 69% of the children did not suffer from an anxiety disorder, a full-blown anxiety disorder does not seem to be a necessary condition for the development of GID.

Chapter 6 addressed parental characteristics to test Zucker and Bradley’s hypotheses about the role of parents in the development of GID. We examined psychological problems in parents of gender dysphoric boys and girls, and compared these results with results from two control groups in order to examine parental psychopathology as a potentially contributing factor in GID.

Furthermore, we examined parent-child interaction style of these parents to test Zucker and Bradley’s hypothesis that parents of gender dysphoric children lack the ability to set limits on their children’s behavior, cross-gender behavior included. In this study, three groups of parents were compared with respect to psychological functioning and parent-child interaction style. The first group (GID group) consisted of parents of 120 children (85 boys and 35 girls) who were referred to our Gender Identity Clinic, the second group was a clinical control group (CC group) consisting of parents of 25 children (18 boys and 7 girls) who were referred to two child psychiatric outpatient clinics, and the third group was a non-referred control group (NC group) consisting of parents of 35 non-referred boys and 27 non-referred girls (total n = 62). Parental functioning was measured with the Symptom Checklist 90-R, the Beck Depression Inventory and with a Dutch questionnaire that assesses personality disorders (‘Vragenlijst Kenmerken Persoonlijkheid’ or VKP). Parent-child interaction was measured with a Dutch questionnaire (the ‘Ouder-Kind Interactie Vragenlijst-Revised’ or OKIV-R). Except for some anxiety symptoms in a subgroup of mothers of boys with GID, parents of children with GID generally did not report more psychological problems than parents of non-referred children. Also, parents of children with GID had a constructive parent-child interaction style. We concluded that parental psychological functioning as such is not a major risk factor for GID development.

In Chapter 7 we reported on a study testing the most prominently assumed biological determinant of GID: prenatal brain exposure to testosterone. We used an indirect method for investigating the effects of prenatal exposure to testosterone: the 2D:4D finger ratio – the relative lengths of the 2nd (“index”) finger and the 4th (“ring”) finger. This marker is assumed to reflect prenatal brain exposure to testosterone and has been intensively studied in relation to postnatal behaviour and sexual orientation (for a meta-analytic study, see Hönnekopp, Bartholdt, Beier, Liebert, 2007). In our study finger ratios of 85 children with GID were compared to finger ratios of 137 control children. Furthermore, we compared the 2D:4D ratios of 96 male and 51 female adult individuals with GID to that of heterosexual male and female adult controls. In the sample of adults with GID, we classified their sexual orientation as either homosexual or non-homosexual (in relation to their birth sex) in order to examine whether or not there were any within-group differences as a function of sexual orientation. We found, as expected, for both hands a normative sex difference in the finger ratio: boys and men had significantly lower finger ratios than girls and females. However, there were no significant differences between the children with GID and their controls and we also found no evidence for an altered 2D:4D ratio in adult males with GID (in both homosexual and non-homosexual patients). We did, however, find a significantly masculinized 2D:4D ratio in adult females with GID (with a co-occurring homosexual orientation). Our own study, together with two other studies, found some support for a different finger ratio pattern in adults with GID.

Social consequences: In chapter 8 we reported on a study examining the social position of children referred to our clinic because of gender dysphoria and investigated whether they are victimized at school. Using a peer nomination technique, we examined whether classmates perceive the gender dysphoric child as a victim of bullying and/or as their friend. Twenty-eight gender dysphoric children (14 boys and 14 girls) and their classmates (n = 495) were included (mean age: 10.5 years). We found that gender-referred children did have friends at school, but hardly any same-sex friends. With regard to social acceptance, we found a sex difference: male classmates rejected gender dysphoric boys, whereas female classmates did not reject gender dysphoric girls. However, neither gender dysphoric boys nor girls were bullied at school. From our study it seems that homophobic bullying is not very prevalent at Dutch schools, and that gender dysphoric children are socially quite well accepted.

Psychosexual outcome: Chapter 9 reports on the psychosexual outcomes of gender-referred children who were assessed in childhood. At the time of the study, they were 16 years of age or older. This was also the first study that prospectively examined whether childhood characteristics were related to psychosexual outcome. We assessed gender dysphoria, sexual orientation and psychological functioning in 54 children (mean age: 18.9; age range at the time of the study: 16–28 years) who had been referred to the Gender Identity Clinic in childhood (mean age: 8.4; age range at first assessment 5–12). Twenty-three other children (Non-responders group), who had been referred in the same period, were not traceable. We found that 27% (n = 21) of the total group of 77 children were still gender dysphoric (Persistence group) and 43% percent of the children (n = 33; Desistence group) were no longer gender dysphoric in adolescence or young adulthood. Children in the Persistence group had more severe GID symptoms in childhood than the children in the other two groups. At followup, nearly all participants in the Persistence group reported having a homosexual or bisexual preference, whereas in the Desistence group only half had a homosexual or bisexual preference. Our study indicated that, despite the fairly high percentage of GID persistence, the majority will desist. Furthermore, the children with more extreme forms of gender dysphoria in childhood were more likely to persist than children with less extreme forms. With regard to sexual orientation, the most likely outcome was homosexuality or bisexuality.

Author/-s:       Madeleine Sophie Christine Wallien

Publication:     Dissertation, Vrije Universiteit Amsterdam, 2008

Web link:          http://dare.ubvu.vu.nl/handle/1871/15646

Background: The aim of this study is to understand the relationship between polycystic ovary syndrome (PCOS), altered hormonal characteristics and insulin resistance in female-to-male (FTM) transsexual patients.

Methods: We studied 69 Japanese FTM cases, aged 17–47 years, who were seen in the Gender Identity Disorder Clinic of Sapporo Medical University Hospital between December 2003 and May 2006. The subjects had never received hormonal treatment or sex re-assignment surgery. Prior to treatment, they received physical examinations entailing measurement of anthropometric, metabolic and endocrine parameters, after which we compared the values obtained according to the presence or absence of PCOS and/or obesity. Insulin resistance was determined using the homeostasis model assessment of insulin resistance (HOMA-IR).

Results: Of the 69 participating FTM cases, 40 (58.0 %) were found to have PCOS. Of the 49 for whom HOMA-IR was calculated, 15 (30.6 %) also showed insulin resistance, whereas of the 59 for whom adiponectin was measured, 18 (30.5 %) showed hypoadiponectinaemia. Of 69 for whom androgens were measured, 29 (39.1 %) showed hyperandrogenaemia. Insulin resistance was associated with obesity but not with PCOS. In contrast, hyperandrogenaemia was associated with both PCOS and obesity.

Cconclusion: FTM transsexual patients have a high prevalence of PCOS and hyperandrogenaemia.

Author/-s:       T. Baba; T. Endo; H. Honnma; Y. Kitajima; T. Hayashi; H. Ikeda; N. Masumori; H. Kamiya; O. Moriwaka; T. Saito

Publication:     Human reproduction, 2007

Web link:          http://www.ncbi.nlm.nih.gov/pubmed/17166864

Hormonally controlled differences in bone mineral density (BMD) between males and females are well studied. The effects of cross-sex hormones on bone metabolism in patients with early onset gender identity disorder (EO-GID), however, are unclear. We examined BMD, total body fat (TBF) and total lean body mass (TLBM) in patients prior to initiation of sex hormone treatment and during treatment at months 3 and 12. The study included 33 EO-GID patients who were approved for sex reassignment and a control group of 122 healthy Norwegians (males, n = 77; females, n = 45). Male patients (n = 12) received an oral dose of 50 μg ethinylestradiol daily for the first 3 months and 100 μg daily thereafter. Female patients (n = 21) received 250 mg testosterone enantate intramuscularly every third week. BMD, TBF and TLBM were estimated using dual energy X-ray absorptiometry (DXA). In male patients, the DXA measurements except TBF were significantly lower compared to their same-sex control group at baseline and did not change during treatment. In female patients, the DXA measurements were slightly higher than in same-sex controls at baseline and also remained unchanged during treatment. In conclusion, this study reports that body composition and bone density of EO-GID patients show less pronounced sex differences compared to controls and that bone density was unaffected by cross-sex hormone treatment.

Author/-s:       Ira R. Haraldsen; E. Haug; J. Falch; T. Egeland; S. Opjordsmoen

Publication:    Hormones and Behavior, 2007

Web link:          http://www.sciencedirect.com/science/article/pii/S0018506X07001298

Males and females are known to be significantly different in regard to their performance on dichotic listening tests with males typically demonstrating a larger Right Ear Advantage (REA) for verbal stimuli (Govier & Bobby 1994; Lake & Bryden 1976; McGlone & Davidson 1973; Wexler & Lipman 1985).

We administered dichotic listening tests to more than 50 male-to-female transsexuals and 15 female-to-male transsexuals as well as comparable groups of controls. In these tests 60 pairs of consonant vowel consonant (CVC) syllables (e.g., kib and tib) were presented, one syllable to each ear simultaneously, via earphones and the respondent asked which syllable or syllables were heard?

Our findings showed persons with the M2F condition produced a response pattern which was significantly different from typical males (p < 0.05). There was no significant correlation between time on gender appropriate hormone treatment and dichotic performance. There is no evidence we know of where this group difference might be due to other environmental or learning factors. This is suggestive of actual brain “hard-wired” differences among M2F transsexuals when compared to typical males; their dichotic performance is more in keeping with their gender than with their sex. So far we have found no comparable sex/gender differences among our F2M subjects. We are currently enlarging our samples.

Author/-s:       Ernie Govier; Milton Diamond

Publication:     Proceedings of the International Academy for Sex Research, 2007

Web link:          http://hawaii.edu/PCSS/biblio/articles/2005to2009/2007-dichotic.html

The study investigates the ability of transsexuals (TS) to recognize facially expressed basic emotions. It was hypothesized that, due to their discomfort in their gender role, this ability might be diminished in TS. In addition it was expected that emotion recognition improves during the course of transgendering, e.g., after having started the Real-life Experience (RLE) which regularly reduces stress levels. Finally it was hypothesized that TS do better in recognizing facial emotions when the person showing them has their desired sex and gender. To test these hypotheses the FEEL-test (Facially Expressed Emotion Labelling) was used. Forty-seven TS and 55 non-transsexual controls matched for age and sex were included in the study. The first hypothesis was confirmed. As regards the second hypothesis, no differences could be found between the groups at different stages in the transition between the two genders. The third hypothesis was also rejected: TS recognized facially expressed basic emotions from male and female stimuli independently of their desired sex.

Author/-s:       Henrik Kessler; Daniela Michallik; Friedemann Pfäfflin

Publication:     International Journal of Transgenderism, 2006

Web link:          http://www.tandfonline.com/doi/abs/10.1300/J485v09n02_02#.Usfd3E2A2oA

Prenatal exposure to androgens has been implicated in transsexualism but the etiology of the condition remains unclear. The ratio of the 2nd to the 4th (2D:4D) digit lengths has been suggested to be negatively correlated to prenatal androgen exposure. We wanted to assess differences in 2D:4D ratio between transsexuals and controls.

Sixty-three male-to-female transsexuals (MFT), 43 female-to-male transsexuals (FMT), and 65 female and 58 male controls were included in the study. Photocopies of the palms and digits of the hands were taken of all subjects and 2D:4D ratios were measured, according to standard published procedures.
Comparison between right-handed individuals revealed that the right-hand 2D:4D in MFT is higher than in control males but similar to that observed in control females. In FMT we found no differences in 2D:4D relative to control females. Our findings support a biological etiology of male-to-female transsexualism, implicating decreased prenatal androgen exposure in MFT. We have found no indication of a role of prenatal hormone exposure in female-to-male transsexualism.

Author/-s:       Harald J. Schneider; Johanna Pickel;  Günter K. Stalla

Publication:     Psychoneuroendocrinology; 2006

Web link:          http://europepmc.org/abstract/MED/16140461

This study examined the impact of sex hormones on functional cerebral hemispheric lateralization and cognition in a group of male-to-female transsexuals receiving cross-sex hormone therapy compared to eugonadal men with a male gender identity. Cerebral lateralization was measured with a handedness questionnaire and a visual-split-field paradigm and cognitive tests sensitive to sex hormone exposure (identical pictures, 3-D mental rotation, building memory) were also administered. Endocrine measures on the day of participation for transsexual and control subjects included total testosterone, free testosterone, estradiol, gonadotropins, and sex hormone binding globulin concentrations. Compared to controls, male-to-female transsexuals had elevated estradiol and sex hormone binding globulin concentrations and suppressed testosterone concentrations. Transsexual subjects showed a trend toward less exclusive right-handedness than controls. No group differences were observed on the visual-split-field or cognitive tasks. No direct associations were observed between endocrine measures and the laterality measures and cognitive performance. Previous observations of female-typical patterns in cerebral lateralization and cognitive performance in male-to-female transsexuals were not found in the current study.

Author/-s:       Amy B. Wisniewski; M. T. Prendeville; A. S. Dobs

Publication:     Archives of sexual behaviour, 2005

Web link:          http://www.ncbi.nlm.nih.gov/pubmed/15803250

Atypical handedness patterns, i.e., persons being less exclusively right-handed, have been found previously in large samples of male and female homosexuals and in small samples of male and female transsexuals compared to controls. The posited role of prenatal androgen influencing both cerebral hemispheric dominance and psychosexual development warrants further study with large samples of transsexuals. 443 male-to-female transsexuals and 93 female-to-male transsexuals were studied for their use of the right or left hand in six common one-handed tasks. Both male and female transsexuals were more often nonright-handed than male and female controls were. Results suggest an altered pattern of cerebral hemispheric organisation in male and female transsexuals.

Author/-s:       Richard Green; Robert Young

Publication:     Archives of sexual behaviour, 2001

Web link:          http://www.ncbi.nlm.nih.gov/pubmed/11725455

Handedness preference was assessed in 205 boys with gender identity disorder and 205 clinical control boys referred for other reasons. Boys with gender identity disorder were significantly more likely to be left-handed than the clinical control boys (19.5 % vs. 8.3 %, respectively). The boys with gender identity disorder, but not the clinical control boys, also had a significantly higher rate of left-handedness compared to three independent, general population studies of nonreferred boys (11.8 %; N= 14 253) by Hardyck, Goldman, and Petrinovich (1975), Calnan and Richardson (1976), and Eaton, Chipperfield, Ritchot, and Kostiuk (1996). Left-handedness appears to be a behavioral marker of an underlying neurobiological process associated with gender identity disorder in boys.

Author/-s:       Kenneth J. Zucker; Nicole Beaulieu; Susan J. Bradley; Gina M. Grimshaw; Anne Wilcox

Publication:    Journal of Clinical Child Psychology and Psychiatry, 2001

Web link:          http://onlinelibrary.wiley.com/doi/10.1111/1469-7610.00773/abstract

To elucidate the relationship between body build, androgens, and transsexual gender identity, anthropometric measurements were assessed in 15 hormonally untreated female-to-male-transsexuals (FMT). Nineteen healthy women (CF) ( X¯   = 22 years; 2 months), and 21 healthy men (CM) ( X¯   = 23;7) were enrolled as controls. Baseline levels of testosterone (T; ng/dl), androstenedione (A4; ng/dl), dehydroepiandrosterone sulfate (DHEAS; ng/ml), and sex-hormone binding globulin (SHBG; μg/ml) were assessed in 12 FMT, 15 CF, and in all CM. No control was under hormonal medication (including contraceptives). Absolute measurements in FMT were in accordance with their biological sex: they showed only small differences from the CF. However, FMT differed from CF in 7 of 14 sex-dimorphic indices of masculinity/femininity in body build. Of these 14 indices, 9 did not show a difference between FMT and CM. Hence, FMT presented a more masculine body build, particularly in fat distribution and bone proportions. Levels of T and A4 were significantly higher in FMT than in CF (T: 54.0 ± 13.8 vs. 41.1 ± 12.8; A4: 244.8 ± 73.0 vs. 190.5 ± 49.3), while DHEAS was higher in CM (3335 ± 951) than in CF (2333 ± 793) and in FMT (2679 ± 1089). Altogether, 83.3 % of FMT and 33.3 % of CF were above normal values for at least one measured androgen. SHBG in FMT (1.21 ± 0.70) and CF (1.87 ± 0.91) was higher than in CM (0.49 ± 0.18) and tended to be higher in CF than in FMT. Unbound T (T/SHBG ratio) was higher in FMT (72.0 ± 67.6) than in CF (26.4 ± 15.1) and correlated positively with manly body shape. Findings are discussed in relation to etiology of transsexualism.

Author/-s:       Hartmut A. G. Bosinski; Inge Schröder; Michael Peter; Reinhard Arndt; Reinhard Wille; Wolfgang G. Sippell

Publication:     Archives of Sexual Behavior, 1997

Web link:          http://link.springer.com/article/10.1023/A%3A1024506427497

Sexual brain organization is dependent on sex hormone and neurotransmitter levels occurring during critical developmental periods. The higher the androgen levels during brain organization, caused by genetic and/or environmental factors, the higher is the biological predisposition to bi- and homosexuality or even transsexualism in females and the lower it is in males. Adrenal androgen excess, leading to heterotypical sexual orientation and/or gender role behavior in genetic females, can be caused by 21-hydroxylase deficiency, especially when associated with prenatal stress. The cortisol (F) precursor 21-deoxycortisol (21-DOF) was found to be significantly increased after ACTH stimulation in homosexual as compared to heterosexual females. 21-DOF was increased significantly before and even highly significantly after ACTH stimulation in female-to-male transsexuals. In view of these data, heterozygous and homozygous forms, respectively, of 21-hydroxylase deficiency represent a genetic predisposition to androgen-dependent development of homosexuality and transsexualism in females. Testicular androgen deficiency in prenatal life, giving rise to heterotypical sexual orientation and/or gender role behavior in genetic males, may be induced by prenatal stress and/or maternal or fetal genetic alterations. Most recently, in mothers of homosexual men--following ACTH stimulation--a significantly increased prevalence of high 21-DOF plasma values and 21-DOF/F ratios was found, which surpassed the mean + 1 SD level of heterosexual control women. In homosexual men as well--following ACTH stimulation--most of the 21-DOF plasma values and 21-DOF/F ratios also surpassed the mean + 1 SD level of heterosexual men. In only one out of 9 homosexual males, neither in his blood nor in that of his mother increased 21-DOF values and 21-DOF/F ratios were found after ACTH stimulation. In this homosexual man, however, the plasma dehydroepiandrosterone sulfate (DHEA-S) values and the DHEA-S/1000 x A (A = androstenedione) ratio were increased before and after ACTH stimulation. Furthermore, highly significantly increased basal plasma levels of dehydroepiandrosterone sulfate were found in male-to-female transsexuals as compared to normal males, suggesting partial 3 beta-ol hydroxysteroid dehydrogenase deficiency to be a predisposing factor for the development of male-to-female transsexualism.

Author/-s:       G. Dörner; I. Poppe; F. Stahl; J. Kölzsch; R. Uebelhack

Publication:     Experimental and Clinical Endocrinology, 1991

Web link:          http://europepmc.org/abstract/MED/1778227