Genderinkongruenz, das Gehirn und die Hormone

People with gender incongruence (GI) and gender nonconforming identities are increasingly visible in the public and in the media. As an umbrella term for various gender-nonconforming roles and identities persons with any form and expression of gender incongruence are called transgender persons. Recent data reveal that up to 0.8% of the population consider themselves as gender incongruent and suffer from gender dysphoria. Most of these persons state that they seriously entertain the idea of gender reassignment. Reasons for the growing numbers of gender incongruent persons across all ages are far from clear. Both societal factors as openness towards nonconforming attitudes and media attention as well as the medical progress enabling successful physical sex reassignment may account for the increasing numbers. Our understanding of the process of typical gender development has increased considerably over the past decades. Sex hormones affect brain and behaviour and play an important role in many differences between men and women. The influence of sex steroids on the structural development of the brain is denoted organisational, whereas the effects of hormones on preexisting structures are classified as activational. However, when it comes to gender and nonconforming identities much remains unravelled. GI has been linked to genetic and hormonal factors, but much of the information comes from single studies or is inconsistent across studies. To date not a single study provides clear evidence for unequivocal linkage of severe gender dysphoria and hormonal disorders or genetic deviations. However, some very captivating studies point to somatic causality. Briefly the current evidence on the etiology of gender incongruence from genetic, neuroanatomical and neuroimaging studies are highlighted