Lorsque le diagnostic de transsexualité est établi selon les critères du DSM-IV, le patient peut débuter un traitement hormonal et ainsi développer les caractères sexuels secondaires du sexe choisi. La thérapeutique est de type androgénique chez les patients F–M et de type estrogénique chez les patients M–F. Ces traitements ne sont pas dénués d'effets secondaires ou de complications plus sévères, dont la thrombophlébite profonde est la plus fréquente. Les formes transdermiques, par l'absence de passage hépatique, engendrent moins de complications que les formes orales. Au vu des contre-indications et des complications potentielles, chaque patient doit être sélectionné de manière rigoureuse. Le suivi endocrinologique se révèle indispensable.

Transsexualism is a sexual identity disorder distinguished by the extreme conviction of belonging to the opposite sex with a total disharmony in the original sex. Diagnosis is established when patients respond to three criteria (DSM-IV): 1) Desire to live and to be accepted as members of opposite sex; 2) Presence of sexual identity disorder for minimal two years; 3) Lack of mental disease or chromosomal anomalies. When diagnosis is confirmed, hormonal treatment can be started and so, improve the secondary sexual characters of selected sex. For patients F–M, treatment is composed of testosterone, most commonly esters of testosterone. For patients M–F, treatment consists of estrogens. These estrogens are frequently associated to an anti-androgen (cyproterone acetate) in the pre-reassignment phase. Avoiding the hepatic way, transdermal form is recommended. Hormonal treatments are not devoid of secondary effects: the most frequent one is venous thromboembolism. Considering contraindications and potential complications, each patient must be selected carefully. The endocrinological follow-up is essential and necessary.