Gender identity disorder

Gender identity disorder is where a person is dissatisfied with their biological sex, because they feel that it is different from the gender they feel they should be. This often leads to a desire to change their appearance with hormones or surgery and live in their preferred gender.

Relevant terms associated with gender identity disorder

GID; Gender dysphoria; transsexualism; male to female (MtF) transsexual; female to male (FtM) transsexual; trans man; trans woman; transman; transwoman

What is gender identity disorder?

‘Biological Sex’ refers to male or female genitalia at birth.

‘Gender’ is a social construct comprised of social, psychological, cultural, and behavioural attributes reflecting what society deems are male or female attributes. Not all people identify as having either strictly male or female genders, which is described as ‘non-binary’.

‘Gender identity disorder’ (GID) is a strong and persistent feeling that a person has a gender identification that is incongruent with their birth sex, which causes psychological distress (gender dysphoria), or a sense of inappropriateness in their current gender role. 

Such a person may choose to change their body through hormone treatment and perhaps ultimately surgery, to have a physical appearance that is more congruent with the gender role that they identify with.

A person born with female sex organs but lives with male gender is called a ‘transman’, whereas a person born with male sex organs but lives with female gender is called a ‘transwoman’.

What causes gender identity disorder?

The underlying cause for GID is unknown. In animals, it is known that there are critical periods of time during pregnancy where alterations in the amount of oestrogen and testosterone in the developing animal can permanently alter masculine or feminine behaviour. However, more research is needed to find out if a similar mechanism could be operating in gender identity disorder. GID is not related to someone’s sexual orientation, and someone with GID may identify with any sexuality including straight, gay, lesbian, pansexual, or bisexual.

What are the signs and symptoms of gender identity disorder?

Gender identity disorder (GID) is the feeling that a person does not belong to the sex in which they were born. In GID, the person is unhappy in their present gender role. Transgender individuals may change their body through hormones and/or surgery so that it is more in keeping with the way they feel it should be. These feelings often lead to the wearing of clothes of their desired gender and changing their role in society accordingly.

It is important to recognise the difference between GID, where the person feels they were born in the wrong gender, and differences of sex development (DSD). DSD covers a range of conditions present from birth, where the development of one or more components of anatomical, chromosomal, or gonadal sex is atypical, but the person generally does not feel they have been born in the wrong gender, although that is still possible.

How common is gender identity disorder?

Gender identity disorder is estimated to occur in 1 in 12,000 men and 1 in 30,000 women.

Is gender identity disorder inherited?

There is no evidence of an inherited cause for gender identity disorder.

How is gender identity disorder diagnosed?

The diagnosis and treatment of gender identity disorder is usually made in accordance with the World Professional Association of Transgender Health guidelines (2022), which recommend that this is undertaken by a mental health practitioner who has experience in working with clients who have problems of gender, alongside a full multidisciplinary team.

A diagnosis of gender identity disorder can only be made if the person has had these feelings about their gender and sexuality for at least 2 years and the person does not have a significant mental health issue such as psychosis that could be causing the gender dysphoria. People with mental health issues can be treated, but they require careful assessment to ensure the gender identity disorder is not related to the underlying mental health issue.

Within the NHS, the route to treatment is for a person to be assessed by local mental health services and, if gender identity disorder is present, refer them on to one of the specialist gender identity clinics.

Blood tests to rule out any endocrine problems are usually taken before any hormone treatment is given and will test levels of pituitary gland hormones luteinising hormone (LH), follicle stimulating hormone (FSH), as well as testosteroneoestradiol and prolactin in the bloodstream. Tests may also be taken to check the person’s chromosomes (karyotype). Tests will also be taken to make sure it is safe to give hormones, and these include liver function tests, kidney tests, a prostate-specific antigen test and a full blood count. 

How is gender identity disorder treated?

The whole treatment process is known as triadic therapy, which is a progressive strategy, consisting of three critical elements – 1. ‘real-life experience’, 2. cross sex hormonal therapy of the desired gender and finally, 3. sex reassignment surgery. As the individual advances through this sequence of therapy with increasingly irreversible effects on their body (and therefore, more significant physical alterations), it becomes increasingly difficult to revert back to their birth sex. It is therefore important that hormonal therapy is undertaken in close collaboration with a mental health professional who is experienced in the assessment of people with gender identity disorder, working closely with the endocrinology team to deliver treatment.

The aim of treatment is to suppress the production of the sex hormones of the person’s birth sex and to give the hormones of their desired gender in order to produce the secondary sexual characteristics of that desired gender. 

In the case of young people, puberty suppressing hormone therapy, a gonadotrophin releasing hormone analogue (GnRHa), may be given once they have commenced puberty, in order to halt pubertal progression. It can also perhaps give the adolescent the opportunity to explore their gender identity and time to consider gender affirming treatment. If the treatment is stopped, then the original sex characteristics will develop. This treatment is not available to children who have not yet reached puberty.

Hormonal replacement with ‘cross sex hormones’ is not available to young people under the age of 16yrs in the UK.

Following hormonal treatment, surgery may be used to modify the genitalia and breasts to alter their appearance to that of the desired gender. This is known as gender reassignment surgery. This is only available in the UK to individuals over 18 years of age.

After surgery, hormone treatment needs to be continued to prevent the complications of not having sex hormone production such as brittle bones (osteoporosis) or early heart disease.

For transwomen, the standard hormonal treatment used at the major NHS provider clinic is oestradiol valerate. The dose given is usually increased over time after an initial three months of therapy. A gonadotrophin-releasing hormone analogue is added to stop testosterone production. To cover the rise in testosterone levels for the first two weeks, cyproterone acetate (an anti-androgen) is also given once daily. Other treatments can include either ethinylestradiol or premarin. However, these preparations are difficult to measure and put the person at a greater risk of thrombosis of the veins than with the use of oestradiol valerate.

For transmen, testosterone treatment begins with an intramuscular dose of testosterone enanthate esters every 4-weeks. The dose is increased every three to four months, but initial doses are usually adequate to suppress menstruation. The aim of therapy is to achieve testosterone levels in the high normal male range one week after the injection, and to have a level at the lower end of the normal male range just prior to the next injection. Other regimens include the use of testosterone gel patches or longer-acting preparations such as a long-acting injection or testosterone implants to get testosterone levels into the normal male range.

Are there any side-effects to the treatment?

Although side-effects are relatively rare, there are a number of issues that a person considering treatment should be aware of.

For transwomen, the side-effects can include:

  • Thromboembolic disease (deep vein thrombosisand pulmonary embolism) – the rate of deep vein thrombosis in transsexual patients is approximately 2.6%. However, in this young population, this represents a risk that is 20 times greater than that of the general population. The majority of these incidents occur during the first two years of treatment. After this period, the risk of thromboembolic disease remains, but at a much lower rate (0.4%).
  • Breast cancer – there have only been few case reports of breast tumours occurring in treated transgender patients, suggesting that the risk of breast cancer following feminising hormone therapy is very low.
  • Hyperprolactinaemia – there may be a slightly increased risk of developing hyperprolactinaemia. This might be evidenced by galactorrhoea, or a milky discharge from the breast.
  • Abnormal liver function – the risk of abnormal liver function is approximately 3% in male-to-female transsexuals. In half of these, the abnormalities continue for more than three months. However, the increases are mild and only rarely require discontinuation of treatment.
  • Fertility – oestrogen therapy leads to suppression of sperm production. Men should be counselled that the treatment will reduce their fertilityand offered the chance of sperm storage if desired prior to any hormone treatment.

For transmen, the side-effects can include:

  • Polycythaemia – testosterone replacement can be associated with an increase in the number of red blood cells, which can thicken the blood (polycythaemia) and lead to an increased risk of stroke. This can occur even in young people as both stroke and heart attacks have been reported in athletes who abuse testosterone.
  • Abnormal liver function –short-term increases in liver function can occur in 4.4% of transmen, which was prolonged (lasting more than six months) in only 6.8% of these. 
  • Gynaecological malignancy – testosterone can be converted to an oestrogen (specifically oestradiol) in the body. This is especially likely to occur when high levels of testosterone replacement are used. The reported risk of overgrowth of the lining of the womb (endometrial hyperplasia) is 15% in transmen. Monitoring of the endometrial thickness by ultrasound scanning every two years is recommended. Hysterectomyis often recommended after two years of testosterone therapy.
  • Transmen with an intact cervix should still undergo regular cervical cancer screening.

What are the longer-term implications of gender identity disorder?

The normal timescale for treatment is that a person has to be living in the opposite gender for a minimum of one year, but more usually two years, before they are eligible for gender reassignment surgery.

Waiting lists are long for individuals to be seen within the gender identity development service, so support should be given to the individual who may be struggling with the wait.

With regard to long-term outcomes, the mortality rate between the trans and general population is not different, which shows that lifelong hormone replacement therapy in this group is very safe.

The legal rights of transpeople have been recognised in the Gender Recognition Act (2004) and the majority of trans people have the right to change their birth certificate when they are stable and established in their new gender role.


Coleman, et al (2022) International Journal of Transgender HealthVolume 23 Issue sup1

Last reviewed: May 2022