The genetic basis of gender dysphoria

Gender dysphoria refers to an incongruence between the sex assigned at birth
and the experienced gender identity. The etiology of gender dysphoria is still
largely unknown. Results of studies from a variety of biomedical disciplines*
endocrine, genetic, and neuroanatomic*support the concept that gender identity
likely reflects a complex interplay of biologic, environmental, and cultural
factors.
Several studies have suggested heritability of gender dysphoria. In particular,
a study by Heylens et al. demonstrated a 39.1% concordance rate for gender
identity disorder (based on DSM-IV criteria) in 23 monozygotic twin pairs but
no concordance in 21 same-sex dizygotic or 7 opposite-sex twin pairs. A
specific genetic cause of gender dysphoria has not been identified. Genes
encoding hormone receptors or enzymes involved in steroidogenesis seemed good
candidate genes and have been investigated but studies have reported
conflicting results.
Most of the genetic studies have been performed in adults with gender
dysphoria, who form a heterogeneous group. The etiology of gender dysphoria may
not be the same for all these individuals; for some social or sexual influences
may play a significant role. Adolescents with early-onset gender dysphoria are
a more homogeneous group and genetics may be a more important determinant of
gender dysphoria in this group.

The purpose of the study is to identify genetic changes that cause gender
dysphoria.

Observational study

Burden: one venapuncture. In patients the blood for DNA extraction will be
drawn at a moment when the patient needs to have a blood sample taken for
monitoring of treatment as part of the routine care so that no extra
venapuncture has to be done for the study.
Risk: none
Benefit: none