Gender dysphoria - Causes of gender dysphoria

The causes of gender dysphoria are not yet fully understood.

Gender dysphoria was traditionally thought to be a psychiatric condition, with its causes believed to originate in the mind.

However, more recent studies have suggested that gender dysphoria is biological and caused by the development of gender identity before birth.

The condition is not a mental illness.

Typical gender development

Much of the development that determines your gender identity – the gender you believe yourself to be – happens in the womb (uterus).

Your biological sex is determined by chromosomes. Chromosomes are the parts of a cell that contain genes (units of genetic material that determine your characteristics). You have two sex chromosomes: one from your mother and one from your father.

During early pregnancy, all unborn babies are female, because only the female sex chromosome (the X chromosome), which is inherited from the mother, is active. At the eighth week of gestation, the sex chromosome that is inherited from the father becomes active; this can either be an X chromosome (female) or a Y chromosome (male).

If the sex chromosome that is inherited from the father is X, the unborn baby (foetus) will continue to develop as female with a surge of female hormones. The female hormones work in harmony on the brain, reproductive organs and genitals, so that the sex and gender are both female.

If the sex chromosome that is inherited from the father is Y, the foetus will develop as biologically male. The Y chromosome causes a surge of testosterone and other male hormones, which starts the development of male characteristics, such as testes. The testosterone and other hormones work in harmony on the brain, reproductive organs and genitals, so that the sex and gender are both male.

Therefore, in most cases, a female baby has XX chromosomes and a male baby has XY chromosomes, and there is no mismatch between biological sex and gender identity.

Changes to gender development

Gender development is complex, and there are many possible variations that cause a mismatch between a person’s biological sex and their gender identity.

Hormonal problems

Occasionally, the hormones that trigger the development of sex and gender may not work properly on the brain, reproductive organs and genitals, causing differences between them. For example, the biological sex (as determined physically by the reproductive organs and genitals) could be male, while the gender identity (as determined by the brain) could be female.

This may be caused by additional hormones in the mother’s system (possibly as a result of taking medication), or by the foetus’s insensitivity to the hormones, known as androgen insensitivity syndrome (AIS). When this happens, gender dysphoria may be caused by hormones not working properly in the womb.

Other rare conditions

Other rare conditions, such as congenital adrenal hyperplasia (CAH), and intersex conditions may also lead to gender dysphoria.

In CAH, the adrenal glands (two small, triangular-shaped glands located above the kidneys) in a female foetus cause a high level of male hormones to be produced. This causes the genitals to become more male in appearance and, in some cases, the baby may be thought to be biologically male when she is born.

Intersex conditions cause babies to be born with the genitalia of both sexes (or ambiguous genitalia). In such cases, it used to be recommended that the child’s parents should choose which gender to bring up their child as. However, it's now considered better to wait until the child can choose their own gender identity before any surgery is carried out.

Read more about disorders of sex development.

Adrenal glands
Two small, triangular-shaped glands that sit on top of the kidneys, high up inside the back of the abdominal wall. They produce adrenaline, steroid hormones and the male and female sex hormones, testosterone and oestrogen.

Chromosomes
Chromosomes are the parts of a body cell that carry genes. A human cell usually has 23 pairs of chromosomes.

Foetus
A foetus is an unborn baby, from the eighth week of pregnancy until birth.

Gender identity
In this article, gender refers to the feeling of being either male or female.

Gender dysphoria
A condition that describes the feeling of mismatch between your biological sex and your gender identity.

Gender identity
Gender identity is your personal sense of knowing which gender you belong to, or the way that you see yourself.

Genes
A gene is a unit of genetic material that determines your body's characteristics.

Hormones
Hormones are powerful chemicals that are produced by the body and have a wide range of effects.

Sex
In this article, sex refers to male or female, the biological sex that you were born with.

Transsexual
A transsexual is someone with an extreme and long-term case of gender dysphoria, who seeks to alter their biological sex to match their gender identity.

Womb
The uterus (also known as the womb) is a hollow, pear-shaped organ in a woman where a baby grows during pregnancy.