Gender Identity Disorder is commonly known as 'transsexualism' and is often confused with 'transvestism'or 'crossdressing'.
Transvestism is defined as: a person, (usually a male) deriving pleasure from dressing in clothes of the opposite sex. Transvestites do not have a desire to change their sex.

Gender identity is the sense of belonging that one feels for a particular sex, not only biologically but also psychologically and socially. It is an extremely subjective entity, which is independent of one's anatomical sex.

Quite apart from the anatomical sex that we are born under (determined by the genitals between the legs ), all of us possess a gender identity.

Transsexualism or gender identity disorder (gender dysphoria ) is a condition in which a person with a normal particular anatomical sexual differentiation is convinced that he or she is actually a member of the opposite sex. This conviction which is accompanied by a profound hatred for the individual's own characteristics,is absolute, overwhelming and unalterable. Transsexualism can be defined as an incongruence between the anatomical sex and gender identity.

So, how does one become 'gender dysphoric'?
Gender identity is very intimately interwoven with the self in all human beings. This makes scientific and logical analysis extremely difficult. It is believed that transsexualism may be a result of the effect of sex-hormone exposure (or lack of it) on the fetal brain.
In the past, some psychiatrists have viewed transsexualism as a form of delusional psychosis. This resulted in the treatment of some transsexuals with antipsychotic medications and electric shock therapy - but to no avail.
Yet another school of thought believed that gender identity development is a learning process that is superimposed on an undifferentiated gender matrix-i.e. gender identity develops as the result of "imprinting" and "conditioning" processes. Thus, transsexualism was viewed as a disorder resulting from improper learning and conditioning.

There has been some studies which have shown that transsexuals have a brain structure which is neuroanatomically different from what is expected of their anatomical sex. There is a particular area in the brain which is essential for sexual behavior. This area is known as the BSTC (bed nucleus of the stria terminals - central subdivision). A female type of BSTC was found in (anatomically)male transsexuals in a pioneering study conducted in the Netherlands. (As of 2002, this has been proven inconclusive. See 'transsexual brians' link below)

Some studies have shown that mothers of female-to-male transsexuals lack a cohesive self and possess an opposite gender envy, which may all be communicated, albeit inadvertently, to the growing child. This results in the child wanting to belong to the opposite sex and identifying herself with her father.

Whatever the reason be, the transsexual's plight is not a happy one and he/she definitely needs empathy and support - not only medically, but also socially.

To summarize, it may be apt to say:
*That transsexualism has its foundation laid before the age of 3 years.
*That the transsexual brain is probably slightly different in its neuroanatomy.
*That a myriad of psychological factors are also operational.
*That rearing practices contribute to its development.
*That a lot more research is needed to understand completely the origin of transsexualism.
*That, like in many other areas of clinical medicine, treatment is often provided on empirical grounds rather than on the basis of a full understanding of the etiology.