David Skidmore’s article “Gender reassignment surgery does not help in our gender-divided society”, demonstrates that being gay does not provide an understanding of the complex affairs of people born with transsexualism. There is a gulf between us that he does not, or does not want to, comprehend.
Transsexuals experience themselves as being of the opposite sex, despite having the biological characteristics of one sex… The present findings of somatostatin neuronal sex differences in the BSTc and its sex reversal in the transsexual brain clearly support the paradigm that in transsexuals sexual differentiation of the brain and genitals may go into opposite directions and point to a neurobiological basis of gender identity disorder.
[T]ranssexualism is a disorder of sexual differentiation, the process of becoming man or woman as we conventionally understand it. Like other people afflicted with errors in the process of sexual differentiation, such as people with intersex conditions, transsexual people need to be medically rehabilitated so that they can live normalized lives as men or women.
The only available, successful and appropriate treatment at present for severe gender dysphoria is gender reassignment treatments, i.e. psychiatric assessments followed by hormone treatment, the real life test and in suitable cases, sex reassignment surgery. This has been confirmed by all long-term studies.
This paradigm is somewhat narrower than the position under Australian common law. The Family Court of Australia in Re Kevin (validity of marriage of a transsexual)  Fam CA 1074 heard detailed evidence from numerous international and domestic medical experts on the transsexual condition. His Honour Chisholm J came to the conclusion that the former narrow definition of “sex” requiring congruency of all three of genitals, gonads and chromosomes, was no longer valid. Finding that the phenomenon of “brain sex” was a biological fact, he said:
In my view, the expert evidence in this case affirms that brain development is (at least) an important determinant of a person's sense of being a man or a woman [at 247] … I see no reason why I should not accept the proposition, on the balance of probabilities, for the purpose of this case [at 248]… In my view, the evidence about the experience of transsexuals, and the strength and persistence of their feelings, fits well with the view that "transsexuals have a sexual brain development contrary to their other sex characteristics such as the nature of their chromosomes, gonads, and genitalia" [at 269]…
I am satisfied that the evidence now is inconsistent with the distinction formerly drawn between biological factors, meaning genitals, chromosomes and gonads, and merely "psychological factors", and on this basis distinguishing between cases of intersex (incongruities among biological factors) and transsexualism (incongruities between biology and psychology) [at 270] … In my view the evidence demonstrates (at least on the balance of probabilities), that the characteristics of transsexuals are as much "biological" as those of people now thought of as inter-sex. The difference is essentially that we can readily observe or identify the genitals, chromosomes and gonads, but at present we are unable to detect or precisely identify the equally "biological" characteristics of the brain that are present in transsexuals [at 272].
Chisholm J held that the factors to be considered in determining a person’s sex included, but were not limited to, the sex of the gonads, genitals, and chromosomes; any hormonal and surgical rehabilitative treatment the person had undergone; the person’s perception of their sexual identity (a manifestation of brain sex); and the perception of others towards them. Following a long line of precedents in Australia, he further held that, post-operatively, a person treated for transsexualism is a member of their re-assigned sex.
The Full Court upheld the decision on appeal and, further, established the position in Australian law that people with transsexualism should not be treated differently to others with intersexed conditions: they should be allowed to choose their sex, affirm it and be accorded full legal status as members of that sex.
It is important here to distinguish, quite clearly, between transsexualism, a biological variation in sexual formation with a fixed gender, and transgender, a psychological disorder in which the sex is fixed but there is variable or cross-gender presentation.