Causes of transsexuality Docter and others, but opposed by Charles Allen Moser, Larry Nuttbrock, Julia Serano, and the World Professional Association for Transgender Health.<section end="factors" /> A 2008 study compared 112 male-to-female transsexuals (both androphilic and gynephilic), mostly already undergoing hormone treatment, with 258 cisgender male controls. Male-to-female transsexuals were more likely than cisgender males to have a longer version of a receptor gene (longer repetitions of the gene) for the sex hormone androgen or testosterone, which reduced its effectiveness at binding testosterone. The androgen receptor (NR3C4) is activated by the binding of testosterone or dihydrotestosterone, where it plays a critical role in
Sexual arousal role in determining how a person will respond in any given sexual situation. On the other hand, a person may be hypersexual, which is a desire to engage in sexual activities considered abnormally high in relation to normal development or culture, or suffering from a persistent genital arousal disorder, which is a spontaneous, persistent, and uncontrollable arousal, and the physiological changes associated with arousal. Sexual arousal causes various physical responses, most significantly in the sex organs (genital organs). Sexual arousal for a man is usually indicated by the swelling and erection of the penis when blood fills the corpus cavernosum.