--- date: "2020-01-26T20:41:55.827Z" lang: "es" title: "What is the Cause of Gender Incongruence" description: "It's the hormones, baby." preBody: '_declaracion' classes: - gdb tweets: - https://twitter.com/LisaTMullin/status/1224039568971710464 - https://twitter.com/LisaTMullin/status/1224040716365524993 - https://twitter.com/LisaTMullin/status/1224041800513380352 - https://twitter.com/LisaTMullin/status/1224041800513380352 - https://twitter.com/LisaTMullin/status/1224042620164296705 - https://twitter.com/LisaTMullin/status/1224043995413639168 - https://twitter.com/LisaTMullin/status/1224044949160611840 siblings: prev: /gdb/es/tratamiento prevCaption: Treating Gender Dysphoria next: /gdb/es/chromosomas nextCaption: But... but... the chromosomes! --- #¿Cuál es la causa de la incongruencia de género? Esto es lo que sabemos hoy. Si has visto Jurassic Park puede que recuerdes esta escena: {!{ {{import '~/img' images.jurassicpark className="card borderless center span34" alt="All vertebrate embryos are inherently female anyway. They just require an extra hormone given at the right developmental stage to make them male."}} }!} Esto no es ciencia ficción, aunque está muy simplificado. En los fetos humanos las gonadas se desarrollan inicialmente en un estado bi-potencial, lo que significa que pueden convertirse tanto en ovarios como en testículos. El gen SRY en el cromosoma Y libera una proteina llamada [Testis-determining Factor](https://es.wikipedia.org/wiki/SRY) (TDF). Esta proteína luego comienza una reacción en cadena con la producción de SOX9 (otra proteína), lo que causa que las células germinales se transformen en las células Sertoli y Leydig que conforman los testículos. Si nunca se produce la TDF o si se interviene entonces las células germinales se transforman en las células Thecca y los folículos que conforman los ovarios. {!{
{{import '~/img' images.fetalgenitals className="card" caption="Source" alt="Fetal development of internal sexual anatomy"}}
}!} Una vez formados, los testículos empiezan a producir una ráfaga de testosterona que típicamente comienza en la octava semana de gestación y continúa hasta la semana 24. Esta ráfaga, [combinada con otra hormona de la placenta](https://www.sciencedaily.com/releases/2019/02/190214153053.htm), es responsable por el desarrollo del pene y del escroto. La formación de los genitales comienza alrededor de la novena semana y se vuelve identificable en la onceava semana. Si la ráfaga no ocurre, o el cuerpo no responde a ella (como en el caso del Síndrome de Sensibilidad Androgénica) entonces los genitales se transforman en la vulva, la vagina y el útero. Si hay una interferencia en este proceso entonces puedes terminar con los genitales equivocados, y ese es el resultado de muchas condiciones intersexuales. A menudo esto es un desarrollo parcial, donde los genitales externos sólo se forman parcialmente, pero las gónadas funcionales existen de todos modos; a veces el infante puede tener genitales femeninos o masculinos completamente funcionales, pero con gónadas no coincidentes. A veces la proteína TDF fracasa en liberarse y el feto genera órganos femeninos reproductivos completamente funcionales, a pesar de la presencia de un cromosoma Y. Esto es conocido como el síndrome de Swyer, y un número desconocido de mujeres puede tener esta condición. En el 2015 [una mujer XY con síndrome de Swyer que nació sin ovarios](https://www.independent.co.uk/news/science/mostly-male-woman-gives-birth-to-twins-in-medical-miracle-10033528.html) llevó y parió exitosamente a un bebé a través de FIV (fertilización in vitro). Usualmente el síndrome de Swyer resulta en ovarios completamente no funcionales, pero [en el 2008 fue encontrada una mujer con síndrome de Swyer](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2190741/) que pasó por la pubertad, menstruaba normalmente, y había tenido dos embarazos sin asistencia. Su condición no fue descubierta hasta que se descubrió que su hija también la tenía. El hecho es que, la vasta mayoría de la población nunca ha sido examinada por su cariotipo, así que no sabemos qué tan comunes son estos casos en realidad. ¿Cómo afecta esto la identidad de género? Bueno, exactamente el mismo proceso que causa que los genitales se diferencien también ocurre en el cerebro. {!{
And it gets even weirder! {{import '~/tweet' ids=[ '1224039568971710464' '1224040716365524993' '1224041800513380352' '1224042620164296705' '1224043995413639168' '1224044949160611840' ] tweets=meta.tweets className="oneblock hide-reply" }}
}!} #### Brain Split El cerebro prenatal no comienza realmente a desarrollarse hasta entre la semana 12 y 24. La corteza cerebralThe cerebral cortex, the thin outer layer of the brain that contains most of what we think of as consciousness, grows substantially during those periods of time. Prior to that, the structure present is more like a scaffolding, the basic parts of the nervous system necessary for bodily function. The primary sulci (the wrinkles in the cerebral cortex that allow for more surface area) [start to form at week 14](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2989000/#Sec5title), well after the genitals have developed. It [has been confirmed multiple times](https://www.the-scientist.com/features/are-the-brains-of-transgender-people-different-from-those-of-cisgender-people-30027) via MRI studies that there are small but significant differences between cis male and cis female brains, differences which align with the gender identities of trans people in the study. Note, **this does not mean that anyone with those differences will have that gender**, because gender identity isn’t that simple, but it provides evidence that there is a clear difference in masculine and feminine brains. A change in the testosterone levels in the fetus after the 11th week can directly impact the masculinization of the cerebral cortex, as well as changes in other parts of the brain structure. This has been examined [over and over again](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4350266/) in studies of female assigned children with CAH (congenital adrenal hyperplasia) and CAIS (complete androgen insensitivity syndrome).

We found a significant relationship between fetal testosterone and sexually differentiated play behavior in both girls and boys.

— Fetal Testosterone Predicts Sexually Differentiated Childhood Behavior in Girls and in Boys
An excess of testosterone in the mother’s body during the second trimester can (and does) cause masculinization of the brain in an externally female fetus, and an interference in testosterone production or uptake can (and does) cause feminisation of an externally male fetus. This interference does not have to be external in origin, either. Any number of genetic traits can cause the brain to respond differently to testosterone. A fairly large study of transgender individuals released in 2018 [found several key genes](https://academic.oup.com/jcem/article/104/2/390/5104458) which were statistically more likely to be longer among trans women (longer, as in having more repeated fragments). Individually these genes may not have an impact strong enough to cause a malfunction of masculinization, but collectively they absolutely could reduce the ability for the fetal brain to masculinize. These genes are all passed from parent to child, giving credence to a tendency for trans parents to have trans children. #### Gender is Biological Sadly, western society has actively prevented a deeper understanding of gender. Ancient civilizations understood it well, but colonialism wiped them off the map. 100 years ago, [scientists in Germany were actively studying](https://en.wikipedia.org/wiki/Institut_f%C3%BCr_Sexualwissenschaft) transgender medicine and made extraordinary advancements, until the nazis burned it all in 1933. Conservative and fascist pressures in the modern day have hindered advancements in transgender healthcare whenever possible. Yet, progress continues, and every few years we learn a little bit more. What we know for certain is that it is not a psychological condition, it is not something caused by trauma or by any external influence, nothing can make a person transgender. It happens in the womb, and is not something that a person can choose to be, any more than they could choose their race or their eye color. It has nothing to do with sexual orientation, it has nothing to do with kinks or fetishes, it has nothing to do with social influences from their parents or from their peers. [Transgender children are as firm in their identities as cisgender children are.](https://www.forbes.com/sites/dawnstaceyennis/2020/12/29/study-transgender-children-recognize-their-authentic-gender-at-early-age-just-like-other-kids/#20bbb14526bf).