Sexual Disorders According to Croucher (2003), there are five layers in the erotic life of human beings. The first of these is sexual identity. This is the physical differentiation between male and female, which is fixed by the end of the first trimester in the development of the foetus. Transsexuals feel that they have the "wrong sex" and therefore the wrong core identity. The second layer is sexual orientation, which refers to hetero- or homosexuality. This is also almost impossible to change, since a genetic component plays a role here. The third layer, which is sexual preferences, refers to the elements of sexual stimulation. For men, for example, this would generally be female body parts, while women are aroused by factors such as intimacy, character, and other more subtle factors. The fourth layer is sex roles, where roles are assigned accordign to gender. This demarcation is strongest in young children. The final, fifth layer is sexual performance. For men, problems in this area include impotence and premature ejaculation, while women experience frigidity and failure to reach orgasm as problems. Both men and women may experience a loss of sexual passion, are acedias.

Both males and females have gonads, or sex glands. These take the form of testicles in the male and ovaries in the female (Magnus Hirschfield Archive for Sexology, 2011). The hormones that are produced in these glands divide into distinct groups: androgens, which are prominent in the male, and estrogens, which are prominent in the female. Both male and female do have both hormones present in their biology. Progesterone is another hormone produced by the female gonads. These are essential for a woman's productive life. All the hormones play an important...

Transgender people experience a hormonal imbalance that makes them feel as if they are the "wrong gender." This is a very strong feeling, producing the idea that the individual can only be happy once the "mistake" has been corrected. This is why these people are willing to undergo an often long, painful procedure to change their gender.
Currently, there are two main theories on the origin of homosexuality: Genetic theories, which include elements of sociobiology; and neurohormonal theories. In genetic theories, it has been suggested that homosexuality can be transferred to offspring by means of genes. Taylor (1997) holds that this is relatively implausible, as twin studies focus on the presence of one major gene, which is unlikely to, by itself, produce a certain sexual orientation. There is also not a large body of evidence to suggest that neurohormonal theories might hold an element of truth. Little consistency has been found in the differences of hormonal levels in homosexual people as compared to heterosexual people. Both theories are therefore subject to further research before any theory can be proved conclusively.

Normal sexual interest refers to sexual attraction among adult people, where both parties share a mutual attraction and respect for each other. Disordered sexual interest often involves personality elements beyond the merely sexual. Dominance and control or submission could form part of these disorders. Hucker defines paraphilia as "intense, recurring sexual fantasies, sexual urges or behaviors…" These involve unconventional objects of desire, such as non-human objects, children or non-consenting adults. Three common types of paraphilia…