Etiology of transsexualism

The etiology of transsexualism, meaning the cause or causes of transsexualism, is an area of interest for many transsexual people, physicians, psychologists, other mental health professionals, and family members and friends of transsexual people. Currently, there is no scientifically proven cause of transsexualism. For many years, many people assumed that transsexualism was a psychological/emotional disorder caused by psychological factors. More recently, research has suggested that the cause of transsexualism may be rooted in biology, and a large segment of the medical profession has come to view transsexualism as a physiological condition rather than a psychological one [ [http://www.gires.org.uk/etiology.php Definition and synopsis of the etiology of adult gender identity disorder] multiple authors] cite journal | last = Zhou | first = Jiang-Ning | coauthors = Michel A. Hofman, Louis J. G. Gooren & Dick F. Swaab | title = A Sex Difference in the Human Brain and its Relation to Transsexuality | journal = Nature | volume = 37 | pages = 68–70 | date = 2 November 1995 | url = http://www.symposion.com/ijt/ijtc0106.htm | doi = 10.1038/378068a0 | accessdate = 2007-02-25 ] cite journal | last = Kruijver | first = Frank P. M. | coauthors = Jiang-Ning Zhou, Chris W. Pool, Michel A. Hofman, Louis J. G. Gooren and Dick F. Swaab | title = Male-to-Female Transsexuals Have Female Neuron Numbers in a Limbic Nucleus | journal = Journal of Clinical Endocrinology & Metabolism | volume = 85 | issue = 5 | pages = 2034–2041 | date = 2000 | url = http://jcem.endojournals.org/cgi/content/full/85/5/2034 | doi = 10.1126 | accessdate = 2007-02-25] . However, as of 2008, definitive physiological causes of transsexualism have not been found.

Possible psychological causes

Many psychological causes for transsexualism have been proposed; including "overbearing mothers and absent fathers", "parents who wanted a child of the other sex", repressed homosexuality, emotional disturbance, sexual abuse, and a variety of sexual perversions and paraphilias, including autogynephilia. None of these theories, however, have been accepted as definitive, with many being criticised for having major flaws.

Harry Benjamin wrote, "Summarizing my impression, I would like to repeat here what I said in my first lecture on the subject more than 10 years ago: Our genetic and endocrine equipment constitutes either an unresponsive [or] fertile soil on which the wrong conditional and a psychic trauma can grow and develop into such a basic conflict that subsequently a deviation like transsexualism can result." [Benjamin, H. (1966). "The transsexual phenomenon." New York: Julian Press, page 85.]

Experience with individuals who were sexually reassigned at birth, in order to correct deformities such as those caused by accidental castration or intersex conditions, suggests strongly that one's mental gender identity is not determined by the environment they are raised in.Fact|date=January 2008 Individuals born male but raised as female, or vice versa, often show the same signs of gender dysphoria as transsexual people; rejecting their assigned gender.Fact|date=January 2008 One notable example was David Reimer. Reimer later suffered depression and heroin addiction in adulthood, which has been taken as proof of gender essentialist biological theories; however, critics of the case study note that his twin brother suffered from the same conditions, and that their depressive moods were likely genetic in origin.

"Curing" transsexualism

Psychological treatments aimed at curing transsexualism are historically known to be unsuccessful. In 1972, the American Medical Association Committee on Human Sexuality published the medical opinion that psychotherapy was generally ineffective for transsexual adults. [Human Sexuality; The American Medical Association Committee on Human Sexuality; Chicago, 1972] A number of other treatments have been tested on transsexual people, including aversion therapy, psychotropic medications, hormone treatments consistent with the patient's birth sex, electroconvulsive therapy, and hypnosis.Fact|date=October 2008 These treatments have also been shown to be ineffective.Fact|date=October 2008

Possible physical causes

One study suggests that transsexualism is based in structural and neurochemical similarities between the brains of transsexual people and brains typical of their gender identity; this study has been alleged to have numerous flaws Fact|date=February 2007. A second study has since replicated the results of the first study and included controls to help eliminate many of the alleged flaws, particularly the study included two individuals who had cross-gender hormone secreting cancers which were significant enough to have caused significant cross-gender development in both individuals. Although transsexualism manifests itself as an anomaly in brain structure in which transsexual people have a neuron density in the central subdivision of the Bed Nucleus of the Stria terminalis region (BSTc), similar to members of their target gender, it is not known whether this is a cause, consequence, or simply a manifestation of transsexualism.

As of December 2006, a new study funded by Ferring Pharmaceuticals was presented at the International Paediatric Endocrinology Symposium in Paris. This studycite journal| author = Hulshoff, Cohen-Kettenis et al. | year = 2006 | month = July | title = Changing you sex changes your brain: influences of testosterone and estrogen on adult human brain structure | url = http://www.eje-online.org/cgi/content/abstract/155/suppl_1/S107 | journal = European Journal of Endocrinology | issue = 155 | pages = 107–114 | doi = 10.1530/eje.1.02248 | id = ISSN|0804-4643 | | volume = 155 ] finds that prior to hormone replacement therapy, transsexual people have brain mass ratios of their birth sex. According to this study, a transsexual person's brain restructures itself to become typically structured for the individual's target sex with the administration of hormone therapy. This study did not analyze differences in specific sexually dimorphic regions of the brain, rather it focused on large-scale differences in overall brain structure. Several animal studies have demonstrated that exposure to cross-sex hormones during certain stages of fetal development can reliably produce cross-sex behaviors in animals. In addition, twin studies have demonstrated a strong heritability of transsexualism. [Concordance for Gender Identity among Monozygotic and Dizygotic Twin Pairs, Diamond, M. and Hawk, S.; American Psychological Association, 2004 Annual Meeting, July 28-August 1, 2004, Honolulu, Hawaii.] This research provides additional evidence that transsexualism may be caused by genetics and in utero hormonal environment. There are several known cases of identical twins who were both transsexual, both male-to-female and female-to-male. Fact|date=February 2007

A recent study from Germany provides additional evidence of a physiological basis for transsexualism. The study found a correlation between digit ratio and male-to-female transsexualism. Male-to-female transsexual people were found to have a higher digit ratio than control males, but one that was comparable to control females. Because digit ratio is known to be directly related to prenatal hormone exposure, this tends to support theories linking such to male-to-female transsexualism. [cite journal | last = Schneider | first = Harald J. | coauthors = Johanna Pickel, Günter K. Stalla | title = Typical female 2nd-4th finger length (2D:4D) ratios in male-to-female transsexuals-possible implications for prenatal androgen exposure | journal = International Society of Psychoneuroendocrinology | volume = 31 | issue = 2 | pages = 265–269 | publisher = Elsevier, Oxford, UK | date = 2006 | url = http://www.sciencedirect.com/science/article/B6TBX-4H16P9S-1/2/ae91dff18b1b99385054e3bf971d47f9 | id = ISSN|0306-4530 PMID 16140461 | accessdate = 2007-02-25 | doi = 10.1016/j.psyneuen.2005.07.005]

There is also evidence from transsexual people born between the 1930s and 1970s that exposure to a synthetic estrogen known as diethylstilbestrol(DES), routinely used at the time to prevent miscarriage and treat morning sickness, may have contributed to disrupting the hormonal balance within the womb. Evidence suggests that an unusually high percentage of physical males whose mothers were known to have taken this medication present as transgender or transsexual, either in childhood or in later life.Fact|date=February 2007

Due to incidents of birth defects and other side effects, the use of DES and other synthetic estrogen compounds has been largely abandoned or replaced with natural estrogens. [ [http://www.cdc.gov/DES DES updates] - Centers for Disease Control and Prevention] Today, with widespread use of certain plastics and other substances, there are likely to be many environmental pollutants which closely mimic the chemical structures of the withdrawn drugs. This suggests that prenatal environmental factors could also influence the development of this condition.

A 2005 study found that prenatal exposure to phthalates reduced the anogenital distance in males. [ [http://www.newscientist.com/article.ns?id=dn7440 'Gender-bending' chemicals found to 'feminise' boys] - New Scientist] Shorter anogenital distances were found to be associated with smaller penises, cryptorchidism, and lower levels of aggressiveness. Although no transsexual patients were included in this study, it suggests that environmental pollutants can affect sexual development in physical males.

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