[Brain characteristics of transgender individuals and consequences of gender assignment treatment]

The differences between the male and female brain in cisgender individuals, those in whom there is no incongruence between the so-called biological sex and the perceived sex, are known. The genetic basis that underlies the differences observed in the brains of transgender individuals compared to cisgender individuals is also becoming known. In transgender individuals, there is a fundamental change in the connectivity of neurons in the body perception network, which may give rise to gender dysphoria. This knowledge allows for the characterization of the transgender condition and distinguishes it from transgender identities such as non-binary gender, gender fluidity, or genderqueer. Articles published assume, from the perspective of depathologization imposed by Gender Ideology, that these differences are due to a different sexual development. The societal acceptance of this perspective over the last two decades paved the way for medical interventions aimed at affirming the perceived gender, different from the genetic sex, through the continuous administration of cross-sex hormones and, in some cases, mutilating surgery. In adolescents and children, affirmation treatment of the perceived gender begins with puberty blockers, which have negative consequences for ossification and growth. The importance and irreversibility of these 'side effects' require the utmost rigor and complete information about them. Spanish law pushes the ideology to the maximum, infringing on the rights of transgender individuals. Medical ethics emphasize the necessity - the right - of a medical and psychological diagnosis, free from ideological approaches, before initiating what is being called treatment. This includes the right to information, prior to consent, about the positive and negative effects of hormonal administration. It also includes the right to the recognition of diversity among transgender individuals, especially the right to research that allows for treating the brain without altering the body. These rights must be recognized and demanded by the laws.