 The research suggests reduced androgen and androgen signaling contributes to the female gender identity of male-to-female transsexuals.The authors say that a decrease in testosterone levels in the brain during development might prevent complete masculinization of the brain in male-to-female transsexuals and thereby cause a more feminized brain and a female gender identity.A variant genotype for a gene called CYP17, which acts on the sex hormones pregnenolone and progesterone, has been found to be linked to female-to-male (FtMs) transsexuality but not MtF transsexuality.