Modern science has found out that gender identity is not a result of one’s upbringing and that it is not a psychological disease (more a physiological - there is a wrong body). No therapy has ever cured any transsexual; many therapies with that goal even ruined the life of the individual completely. A male to female transsexual really has a female self and a female to male really has a male one! But what is the cause for this self? What is the reason for our gender identities?
People usually assume that chromosomes define what we are, but members of many faculties of the medical community did already criticize this popular view. It may be true that in most cases the chromosomes and the gender identity of a person are in accordance with each other, but there are many people - not only transgenders - where this is not the case. Intersexuals - of which the so called "hermaphrodites" are the most well known - are such individuals. Many of them have a composition of chromosomes that are quite unusually (like XXY), there are also cases of intersexual girls who are born with completely female looking genitals, a feminine gender identity and a normal male chromosomal structure (XY). This latter condition is called CAIS (complete androgen insensitivity syndrome) and it may be related to the condition of transgenderism. In the CAIS cases the chromosomal - genetic make up of the embryo is male, but the hormonal developments in the female womb cause the child to "wire" female brain structures. If this condition holds on it also causes the child to develop female looking organs. When growing up these girls usually always define themselves as completely female and they usually are defined as such by outsiders as well.