BACKGROUND GID is a psychic disorder in which an otherwise normal person feels like he/she is a member of the opposite sex to which she/he belongs biologically. These patients require hormonal treatment to suppress the somatic characteristics of their own sex and to develop the somatic characteristics of the other sex. After psychotherapy and a period of hormonal treatment, they undergo surgical sex reassignment which, in the case of FtM subjects, consists of hystero-adnexectomy, reductive mastoplasty and possibly penile reconstruction. Thereafter, and for their entire life, they must be treated with testosterone (T) to maintain androgen-dependent physiological functions.