We do not know for sure why some people are transgender or gender diverse. People who study this have found some things. They need to do more work before they know for sure.
Two things shape who we are: heredity and environment. These are sometimes called nature and nurture, but those terms are not quite right. Most experts believe both heredity and environment shape who we are. They do not all agree on how much heredity and how much environment.
Heredity means that you got a trait from your parents when their genes combined to form you. People who study genes have found some gene patterns that may be more common in trans and gender diverse people. For more on this, see this page on transgender genes.
Environment means everything else that shapes who you are. This includes everything from what your mother ate while she was pregnant with you to things you are taught.
Current isuues
Disease models of gender identity and expression
Some people think being trans or gender diverse is a disease. They have made up many disease models to describe us. Many of us think this is wrong. We think it is a trait that is neither good or bad. People used to say being gay is a disease. Most people no longer think that is true.
Concern about a “cause”
Scholars such as Daryl Bem have argued that asking “What causes homosexuality?” is “both politically suspect and scientifically misconceived.” The same argument can be made regarding gender identity issues. See Exotic Becomes Erotic for an interesting overview of this concept applied to sexual orientation.
Congenital brain development issues
A congenital trait is something that is present at birth. Several scientific hypotheses examine the effects of hormones during fetal development. One notable hypothesis examines a synthetic hormone called diethylstilbestrol (DES) and its effect on developing fetuses. This drug was administered between 1938 and 1971 to prevent miscarriages, but it has since been linked to several developmental issues in exposed fetuses. Some transwomen born during that period have created essays and discussion groups.
The overview below summarizes recent scientific research. While the studies listed below do not provide conclusive evidence, they suggest that this hypothesis has enough scientific credibility to merit additional research. The text below is taken from the document housed on the GIRES site.
UK organization GIRES made this summary:
Further reading
LINK: A defining moment in our history: examining disease models of gender identity
LINK: Atypical Gender Development – A Review by GIRES
LINK: Depathologizing gender identity by Katherine Wilson, Ph.D. http://www.transgender.org/tg/gidr/
LINK: What Causes Transsexualism? by Professor Lynn Conway
LINK: Biological Correlations of Atypical Gender Identities
LINK: Exotic Becomes Erotic by Daryl Bem, Ph. D.