Update on the Biology of Transgender Identity

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

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

Challenges in assessing personality of individuals with Gender Dysphoria with the SWAP-200

BACKGROUND

Personality assessment can be useful to better understand the complexity of transgender and transsexual people. In particular, the Shedler Westen Assessment Procedure-200 (SWAP-200) is a measure that provides an accurate dimensional evaluation of personality. When assessing gender non-conforming people, however, clinicians can encounter some difficulties in giving appropriate ratings to all the items.

PURPOSE OF THE REVIEW

A brief guide to the use of SWAP-200 with transgender patients is provided, taking into account three areas of psychological functioning: identity, relationships and sexuality. The authors review, one by one, the SWAP-200 items related to these areas, and, relying on their clinical experience and on scientific literature on Gender Dysphoria, they propose recommendations for making personality diagnoses meaningful.

CONCLUSION

This paper facilitates a better clinical understanding of transgender people, and help clinicians to be more knowledgeable in the assessment of this heterogeneous population.

Altered White Matter and Sensory Response to Bodily Sensation in Female-to-Male Transgender Individuals

While most people take identification with their body for granted, conditions such as phantom limb pain, alien hand syndrome, and xenomelia suggest that the feeling of bodily congruence is constructed and susceptible to alteration. Individuals with xenomelia typically experience one of their limbs as over-present and aversive, leading to a desire to amputate the limb. Similarly, many transgender individuals describe their untreated sexed body parts as incongruent and aversive, and many experience phantom body parts of the sex they identify with (Ramachandran, 2008). This experience may relate to differences in brain representation of the sexed body part, as suggested in xenomelia (McGeoch et al., 2011). We utilized magnetoencephalography imaging to record brain activity during somatosensory stimulation of the breast-a body part that feels incongruent to most presurgical female-to-male (FtM)-identified transgender individuals-and the hand, a body part that feels congruent. We measured the sensory evoked response in right hemisphere somatosensory and body-related brain areas and found significantly reduced activation in the supramarginal gyrus and secondary somatosensory cortex, but increased activation at the temporal pole for chest sensation in the FtM group (N = 8) relative to non-transgender females (N = 8). In addition, we found increased white matter coherence in the supramarginal gyrus and temporal pole and decreased white matter diffusivity in the anterior insula and temporal pole in the FtM group. These findings suggest that dysphoria related to gender-incongruent body parts in FtM individuals may be tied to differences in neural representation of the body and altered white matter connectivity.

Personality and Attachment in Transsexual Adults

The main aim of this study was to investigate the associations between personality features and attachment patterns in transsexual adults. We explored mental representations of attachment, assessed personality traits, and possible personality disorders. Forty-four individuals diagnosed with gender identity disorder (now gender dysphoria), 28 male-to-female and 16 female-to-male, were evaluated using the Shedler-Westen assessment procedure-200 (SWAP-200) to assess personality traits and disorders; the adult attachment interview was used to evaluate their attachment state-of-mind. With respect to attachment, our sample differed both from normative samples because of the high percentage of disorganized states of mind (50% of the sample), and from clinical samples for the conspicuous percentage of secure states of mind (37%). Furthermore, we found that only 16% of our sample presented a personality disorder, while 50% showed a high level of functioning according to the SWAP-200 scales. In order to find latent subgroups that shared personality characteristics, we performed a Q-factor analysis. Three personality clusters then emerged: Healthy Functioning (54% of the sample); Depressive/Introverted (32%) and Histrionic/Extroverted (14%). These data indicate that in terms of personality and attachment, GD individuals are a heterogeneous sample and show articulate and diverse types with regard to these constructs.

THE BIOLOGIC BASIS OF TRANSGENDER IDENTITY: 2D:4D FINGER LENGTH RATIOS IMPLICATE A ROLE FOR PRENATAL ANDROGEN ACTIVITY

OBJECTIVE

The biologic basis for gender identity is unknown. Research has shown that the ratio of the length of the second and fourth digits (2D:4D) in mammals is influenced by biologic sex in utero, but data on 2D:4D ratios in transgender individuals are scarce and contradictory. We investigated a possible association between 2D:4D ratio and gender identity in our transgender clinic population in Albany, New York.

METHODS

We prospectively recruited 118 transgender subjects undergoing hormonal therapy (50 female to male [FTM] and 68 male to female [MTF]) for finger length measurement. The control group consisted of 37 cisgender volunteers (18 females, 19 males). The length of the second and fourth digits were measured using digital calipers. The 2D:4D ratios were calculated and analyzed with unpaired t tests.

RESULTS

FTM subjects had a smaller dominant hand 2D:4D ratio (0.983 ± 0.027) compared to cisgender female controls (0.998 ± 0.021, P = .029), but a ratio similar to control males (0.972 ± 0.036, P =.19). There was no difference in the 2D:4D ratio of MTF subjects (0.978 ± 0.029) compared to cisgender male controls (0.972 ± 0.036, P = .434).

CONCLUSION

Our findings are consistent with a biologic basis for transgender identity and the possibilities that FTM gender identity is affected by prenatal androgen activity but that MTF transgender identity has a different basis.

ABBREVIATIONS

2D:4D = 2nd digit to 4th digit; FTM = female to male; MTF = male to female.