Gender identity disorder, as identified by psychologists and physicians, is a condition in which a person has been assigned one gender, usually on the basis of their sex at birth (compare intersex disorders), but identifies as belonging to another gender, and feels significant discomfort or being unable to deal with this condition. It is a psychiatric classification and describes the problems related to transsexuality, transgender identity and more rarely transvestism. It is the diagnostic classification most commonly applied to transsexuals.
The core symptom of gender identity disorders is gender dysphoria, literally being uncomfortable with one's assigned gender.
This feeling is usually reported as "having always been there" since childhood, although in some cases, it appears in adolescence or adulthood, and has been reported by some as intensifying over time.[1] Since many cultures strongly disapprove of cross-gender behaviour, it often results in significant problems for affected persons and those in close relationships with them. In many cases, discomfort is also reported as stemming from the feeling that one's body is "wrong" or meant to be different.
Some medical and psychological professional have tried to cure (dissuade) individuals from their transgender behaviour/feelings at least since the mid-19th century. Only occasionally have such cures been reported, and almost all such reports lack substantiation. (Overlapping reports suggest some in fact were cured several times, implying that these individuals were not cured at all.) While over three decades ago the American Psychiatric Association (APA) removed homosexuality from the Diagnostic and Statistical Manual of Mental Disorders (DSM), and many believed sexual identities were finally freed of medicalized stigma, today many LGB and "gender non-conforming" youth and adults remain vulnerable to diagnosis of psychosexual disorder under the GID diagnosis which immediately replaced homosexuality in the DSM version III. Thus many LGB and gender variant youth and adults, including transgender individuals, are still directed to conversion therapies.

Today, most medical professionals who provide transgender transition services now reject conversion therapies as abusive and dangerous, believing instead what many transgender people have been convinced of: that when able to live out their daily lives with both a physical embodiment and a social expression that most closely matches their internal sense of self, transgender and transsexual individuals live successful, productive lives virtually indistinguishable from anyone else (e.g. Lynn Conway’s “Success Pages” in External Links below). “Transgender transition services”, the various medical treatments and procedures that alter an individual's primary and/or secondary sexual characteristics, are thus now considered highly successful, medically necessary interventions for many transgender persons, including but not limited to transsexuals, especially those who experience the deep distress of body dysphoria. The World Professional Association for Transgender Health (WPATH, formerly HBIGDA) Standards of Care (Version 6 from 2001) are considered by some as definitive treatment guidelines for providers. Other Standards exist (see those discussed in Standards of care for gender identity disorders, including the guidelines outlines in Gianna Israel and Donald Tarver's classic 1997 book "Transgender Care". Several health clinics in the United States (e.g. Tom Waddell in San Francisco, Callen Lorde in New York City, Mazzoni in Philadelphia) have developed “protocols” for transgender hormone therapy following a “harm reduction” model which is coming to be embraced by increasing numbers of providers. In their 2005 book Medical Therapy and Hormone Maintenance for Transgender Men, Dr. Nick Gorton et al suggest a flexible approach based in harm reduction, “Willingness to provide hormonal therapy based on assessment of individual patients needs, history and situation with an overriding goal of achieving the best outcome for patients rather than rigidly adhering to arbitrary rules has been successful.”
Medical body interventions and procedures are often necessary to enable living socially in a gender role that more closely matches one's gender identity, and many assume that being accurately perceived by others is a primary goal of body transformations. However, for those transgender individuals who experience the deep internal distress of body dysphoria, the effects wrought by physical changes - hormones, surgeries, or other procedures - go much deeper than surface appearances and are far from cosmetic. The primary effects of hormonal and/or surgical interventions are experienced directly by self, internally, increasing a sense of internal harmony and well-being at the deepest psychological and emotional levels, as well as through the physical senses especially proprioception - the body's own knowledge of itself. Many medical professionals have come to consider "post-transition" transsexuals to be fully cured of their dysphoria or any other disorder.

Therefore, many feel the diagnosis of gender identity disorder is at best only temporarily applicable, if ever.[citation needed] Indeed, through transition many transsexuals are able to bring their body and their lived/expressed gender into alignment with the internal sense of self. Thus, many post-transition transsexuals cease to regard themselves as "trans" in any sense: many transwomen (male-to-female) self-describe as "women" and, similarly, many transmen feel themselves to be unequivocally "men." While some of these individuals may require continued hormone replacement therapy (estrogen or testosterone, respectively) throughout their adult life, such HRT is not substantially different from the HRT often prescribed for cisgender females or males (not only are dosage levels similar, so are the effects of lack of treatment). Thus, many medical providers in the United States now routinely prescribe such HRT under the same medical codes used for other women and men.

Achieving basic human rights for all transgender persons undoubtedly requires increased social acceptance of each individual's own expression of their identity, regardless of their birth gender or social role expectations. However, for those transgender individuals who experience the internal distress of body dysphoria, social acceptance of variation, while vastly important, will not be sufficient. For this segment of the transgender community, some medical services and procedures will also be required in order for these individuals to feel aligned with their bodies and for the distress of body dysphoria to be fully alleviated.

Gorton et al. underscore the importance of medical interventions for some transgender individuals, warning that “Providers must however consider not only the adverse effects of providing hormones but the adverse consequences of denying access to medically supervised hormonal therapy. Non-treatment of transgender patients can result in significantly worse psychological outcomes.” Failure to treat and/or delayed access to transition may have tragic, indeed catastrophic, results for some transgender individuals. It is well-known that the rate of teen suicides is highest for LGBT youth. Recent studies now suggest that suicide rates are highest for transgender youth and adults, especially those unable to live their gender identity and those unable to access transgender transition services. Gorton et al. suggest rates as high as 20% for untreated transsexuals. However, even when transition services are available, suicide rates are still higher than for the general population.

What is transgender and transsexual? Is it a gender identity disorder?
Transgender is generally used as a catch-all umbrella term for a variety of individuals, behaviours, and groups centered around the full or partial reversal of gender roles ; however, compare other definitions below.
A transgender symbol, a combination of the male and female sign with a third, combined arm representing transgender people.
The term remains in flux, but the most accepted definition is currently:
People who were assigned a gender, usually at birth and based on their genitals, but who feel that this is a false or incomplete description of themselves.
Another one is: Non-identification with, or non-presentation as, the gender one was assigned at birth.

Transgender people may or may not have had medical gender reassignment therapy, also called sexual reassignment surgery, and may or may not have any interest in such a procedure. In other words, not all transgender people are necessarily transsexual.

When referring to the two basic "directions" of transgender, the terms transman for female-to-male (which may be further abbreviated to FtM) transgender people and transwoman for male-to-female (which may be further abbreviated to MtF) transgender people may be used. In the past it had always been assumed that there were considerably more transwomen than transmen. However, the ratio is approaching 1:1.

Transgender can include a number of sub-categories, which, among others, including transsexual, cross-dressing, transvestite, consciously androgynous people, people who are genderqueer, people who live cross-gender, drag kings and drag queens, among many others. Usually not included, because in most cases it is not a gender issue (although in practice the line can be hard to draw) are transvestic fetishists.

Many people also identify as plainly transgender, although they may fit the definition of any of the previously mentioned categories as well.

The extent to which intersex people (those with genitalia or other physical sexual characteristics that not strictly either male or female) are included in the transgender category is often debated. Not all intersex people have a problem with the gender role they were assigned at birth, nor do all intersex people have any problems with gender identity. Those who have, though, are sometimes included in transgender.

The opposite of transgender is cisgender.
The terms "gender dysphoria" and "gender identity disorder" are used in the medical community to explain these tendencies as a psychological condition and the reaction to its social consequences. Strictly speaking, gender dysphoria and gender identity disorder are considered to be mental illnesses, as recorded in the Diagnostic and Statistical Manual of Mental Disorders (DSM), the standard for mental healthcare professionals. Unfortunately, many mental healthcare providers know little about transgender life, and persons seeking help from these professionals often end up educating the professional rather than receiving help. Among those therapists, psychologists, etc. who do know about transgender issues, many believe that transitioning from one sex to another "the standard transsexual model" is the best or only solution. This usually works well for those who are transsexual, but often far less well for those cross-gender people who do not identify as plainly male or female.
Originally, the term transgender was coined in the 1970s by Virginia Prince in the USA, as a contrast with the term "transsexual," to refer to someone who does not desire surgical intervention to "change sex," and/or who considers that they fall "between" genders, not identifying strictly to one gender or the other, identifying themselves as neither fully male, nor female.

Transgenderists and non-operative transsexuals
Often in older writings (pre ~ 1990s), but rarely today, the term transgender is used to refer to these "non-op transsexuals" or "non-op transpeople" who live as the gender opposite to their birth gender and, though sexual reassignment surgery is possible, have chosen not to undergo it; sometimes they also choose not have other medical gender reassignment therapy. However, sometimes, for example in the Netherlands (but not in the rest of Europe), the term transgender is still in use for this particular group instead of being used as such an umbrella term.

This group is also sometimes known as "transgenderists" or "non-op transsexuals". Many point out that the term "non-op transsexual", however, is very far from ideal, in that it seems to be an oxymoron (people who want to become the other sex yet don't) or a case of defining people by what they are not rather than what they are. Unfortunately, there seems to be no perfect term in English for this sort of person as of yet.
Transgender as "in between"
Transgender is sometimes also used specifically in an "in-between" sense, rather than as an umbrella term.

A newer related term is "genderqueer", which refers to the mixing of qualities traditionally associated with "male" and "female," and can also refer to the "in-between" sense sometimes associated with transgender or transgenderism.
Transsexual people are people who desire to have, or have achieved, a different physical sex from that which they were assigned at birth. One typical (though oversimplified) explanation is of a "woman trapped in a man's body" or vice versa; many transsexual women state that they were in fact always of the female gender, but were assigned the male gender as a child on the basis of their genitals, and having realized that they are female, wish to change their bodies to match; transmen, naturally, feel exactly the opposite.

The process of physical transition for transsexuals usually includes hormone replacement therapy and may include sexual reassignment surgery (a.k.a. gender reassignment surgery). For transwomen, electrolysis for hair removal is often required, while many transmen have breast-reduction surgery as early as possible, whether accompanied by genital surgery or not.

Some spell the term transexual with one s in order to reduce the association of their identity with psychiatry and medicine.
Terminology and concepts, compared to transgender
Transgender is often used as a euphemistic synonym for transsexual people by some. One set of reasoning for this is that it removes the conceptual image "sex" in "transsexual" that implies transsexuality is sexually motivated, which it is not. This usage is problematic because it can cause transgender people who do not identify as transsexual to be confused with them. It also seems to remove the issue of social presentation (gender, in its social sense) from the question, even though gender role and presentation is an important part of the equation.

Furthermore, many transsexuals reject the term "transgender" as an identification for themselves, either as a synonym or as an umbrella term. They advance a number of arguments for this. One argument is that the use of the umbrella term inaccurately subsumes them and causes their identity, history, and existence to be marginalized. Another is that they perceive the term to be the breaking down of gender barriers, whereas transsexual people themselves usually identify as men or as women -- just not as they were assigned at birth. A third occasionally mentioned is that they did not change gender at any point -- they have always had their gender (identity), and the difficulty is their sex (anatomy), which they desire to change. However, others point out that transsexual people do change their gender role at some point, and that most non-transsexual transgender people always had their gender identity, too.

A more problematic dispute with the use of the term "transsexual" is that it refers to processes of chemical and/or anatomical modification that do not actually render an individual reproductively viable after transition processes, nor change sex chromosomes. Particularly, criticism of transsexual women by some feminists includes the contention that their transition is cosmetic rather than fundamental, and they are thus not "really" changing their sex at all (thus the use of transgender). These critics claim that the presumption of reproductive viability is what distinguishes "women" from "men". This argument is used to discount the rights of identification and association with other women that transsexual women might claim. However, many arguments that link whether someone is a "woman" or a "man" based on reproductive capability, or chromosomes, fall apart when considering non-transsexual people who are infertile or non-transsexual men or women who have a chromosomal configuration different from other men and women in the general population.

Probably many of these problems are associated with the history of the term "transgender" and its other definitions; see above.

To respect the identity of those transsexual people who do not identify as transgender, the constructions trans, trans*, or transgender and transsexual sometimes are used to describe all transpeople.

Further, many people who this article would define as transgender reject the term altogether, along with other related terms (transsexual, crossgender, etc.). This is most commonly seen with people who have changed sex but who do not define themselves as transsexual. A common statement is that a transsexual is someone who is undergoing a change from one sex to another; someone who has already done so is simply a "man" or a "woman". This brings up issues of the extent to which someone who is not a part of a group may define it, also seen in the case of, for example, "men who have sex with men" (MSMs), who do not see themselves as homosexual but could still be defined as such.
Cross-dressing, transvestism, drag king, drag queen, transvestic fetishism
A person who is cross-dressing is any person who, for any reason, wears the clothing of a gender other than that to which they were assigned at birth. Cross-dressers may have no desire or intention of adopting other behaviours or practices common to that gender, and particularly does (currently) not wish to undergo medical procedures to facilitate physical changes. Contrary to common belief, most male-bodied cross-dressers prefer female partners.

Drag involves wearing highly exaggerated and outrageous costumes or imitating movie and music stars of the opposite sex. It is a form of performing art practiced by drag queens and drag kings. Drag is often found in a gay or lesbian context. The term "drag king" can also apply to people from the female-to-male side of the transgender spectrum who do not see themselves as exclusively male identified, therefore covering a much wider ground than a "drag queen".

Transvestic fetishism is a term used in the medical community to refer to one who has a fetish for wearing the clothing of the opposite gender. This is considered a derogatory term by some, as it implies a hierarchy of value in which the sexual element of transgender behaviour is of low social value. Many reject the term "transvestite" for this reason, preferring cross-dresser instead. It is often difficult to distinguish between fetishism that happens to have female clothing as an object and transgender behaviour that includes sexual play. Some people feel that transvestic fetishism does not count as cross-dressing.
"Transgender" is also used to describe behaviour or feelings that cannot be categorized into these older sub-categories, for example, people living in a gender role that is different from the one they were assigned at birth, but who do not wish to undergo any or all of the available medical options, or people who do not wish to identify themselves as "transsexuals", "men" or "women", and consider that they fall between genders, or transcend gender.

Some people who present as female, but with male genitalia may have been born intersexual but may also be transsexual or transgender, who do transition (taking oestrogens and/or other methods) to achieve some desired secondary sex characteristics, but not sexual reassignment surgery. Sometimes these individuals are referred to as ladyboy or shemale (compare there), but these terms are considered derogatory by many, including most transgender or transsexual people not working in the sex industry.
(Trans-)gender identity is different from, though related to, sexual orientation. Sexual orientations among transgender people vary just as much as they do among cisgender people. Although few studies have been done, transgender groups almost always report that their members are more likely to be attracted to those with the same gender identity, compared to the population as a whole; that is, transwomen are more likely to be attracted to other women, and transmen are more likely to be attracted to other men. Many transgender people who are attracted to others of the same gender will identify as gay, lesbian, or bisexual.

Note that in the professional literature, "homosexual" and "heterosexual" are very often used respective to clients' birth sex, instead of their desired sex. Transgender people may feel misunderstood by caregivers because of this practice; it is also quite confusing when a relationship that is considered gay or lesbian by both partners is labeled heterosexual, or a relationship that consists, as far as the partners are concerned, of a man and a women is labeled homosexual. The existence of transgender people and their sexual relationships points to certain inadequacies of language.

Many Western societies today have some sort of procedure whereby an individual can change their name, sometimes also their legal gender, to reflect their gender identity; see Legal aspects of transsexualism. Medical procedures for transgender people are also available in most Western and many non-Western countries. However, because gender roles are an important part of many cultures, those engaged in strong challenges to the prevalence of these roles, such as many transgender people, often have to face considerable prejudice.
Transgender in non-Western cultures
This article describes primarily Western modes of transgenderism. Many other cultures have or have had similar phenomena:
The so-called berdache in many Native American groups is recognized as a separate gender, a woman-living-man, not as a man who wants to be a woman. The term "berdache" is a misnomer, however, as no Native American group actually used the term; different ethnic groups had different names for the role, such as the winkte. The husband of such a person is not viewed as being gender-different themself, but as a normal male. In some societies there is a corresponding gender for man-living-women ( amazons).
In Thai culture, there is the kathoey, who is very similar to the English definition of transgender, but is sometimes broader, including effiminate gay males moreso than "transgender" does.
South Asian cultures have hijra, usually genetic males who have been castrated and live as women.
Chinese cultures have a wide variety of transgender modes of existence. See transgender in China.
Gender identity disorder
Transgender and transsexualism are only regarded as a disorder if they make a person unhappy and unsatisfied, or causes problems in relations to other people. If they are happy with it, and it causes no problem, it is a personality trait, but not a disorder.
Persons with a gender identity disorder have had strong feelings since childhood that they were born in the wrong body. They want to belong to the opposite sex, e.g. they want to be a woman instead of a man and vice versa. This can be seen in children when they keep on indicating that they want to belong to the opposite sex, want to wear clothes of the opposite sex and have a strong and continuous preference for playing the role of the other sex or pretending to belong to this sex. They also want to play games and have pastimes of the other sex and preferably play with pals of the other sex.

Note that transgender need not include a wish to have sex playing another sex role than born with. Note also that some people normally use their normal gender role, but sometimes wish to try out the reverse gender role.

In adolescents this disorder is very noticeable by signs like wishing to belong to the opposite sex, living like someone of the other sex, being treated as someone of the other sex or be convinced that he or she has the typical feelings and reactions of the other sex. Transsexuals are not transvestites; transvestites are people who every now and then feel good in the clothes of the other sex, but don't want to live like this forever.