This is a pretty long one but I think I can help you out :). So, nobody has really found out why someone may experience gender dysphoria (which if you don't know what it is already, it is when a person identifies with the opposite gender and or discomfort with their assigned gender). However, there is a biological basis that scientists have found for why males are more likely to experience this than females. The reason is because when a baby is made, males have both an X and Y chromosome, while girls have two X chromosomes. The Y chromosome in males deals with developing the male genitals in the baby so babies without the Y chromosome continue developing as females (hint: that means we all basically start out as females). Anyways, when the baby with the Y chromosome develops male testes, they start to release significant amounts of male hormones during the 3rd month of pregnancy, which develops male differentiation more.The surge of male hormones occurs again sometime between the 2nd and 12th week after the baby is born. Its important to know that this same thing doesn't happen in females, no hormones are released like in the males. So, if these male hormone surges don't occur in significant amounts or in a certain amount of time, the masculinization of the developing infant won't happen. Also, these hormonal surges can be affected by many things such as maternal stress (or stress on the mother), maternal medications, or a disorder in the mother's endocrine system. Also, studies have shown that there is a significant difference in the volume of a portion of the hypothalamus that is essential for sexual behavior in people who experience gender dysphoria. These initial studies confirm that one's sense of gender resides in the brain and may be chemically determined. Lastly, environmental conditions also affect one's sense of gender. This means things like how your family is, reinforcement by parents, family, and friends all can determine a child's sense of gender which then leads to what society considers sex-appropriate or inappropriate behavior. Hope this helps!
