Picture taken at a 2013 rally for transgender equality

Biological sex and ‘brain sex’

What happens when the two don’t match?

Some people have an overpowering feeling, often from childhood onwards, that they have been born in a body of the wrong physical sex. They may therefore want to change their body to fit their inner ‘gender identity’. (While sex refers to biology and anatomy, gender refers to an internal sense of being masculine or feminine – see our ‘Sex and Gender’ issue for more on this topic.)

The mismatch between biological sex and gender identity can create deep unhappiness, anxiety and psychological pain (gender dysphoria). As a result, people with gender dysphoria often suffer mental health problems.

A 2009 report suggested that the number of people seeking treatment for gender dysphoria was doubling around every five years. It estimated in the report that gender dysphoria affected around one in every 5,000 people in the UK.

The answer for many (although by no means all) transgender people is to change their physical sex through surgery and/or hormone replacement therapy – known as sex reassignment therapy/surgery. Other transsexuals choose to live in their gender role without adjusting their sex, and do this by dressing and acting as the man or woman they wish to be.

Although surgery and hormone treatment are accepted medical interventions, individuals undergo a period of counselling before treatment starts.

The origins of transsexuality are unclear, but it may have a biological basis. Hormones produced during pregnancy may interact with genes to affect the way a baby’s brain develops – as male or female. One particular region of the brain known as the bed nucleus of the stria terminalis differs in size in men and women. A study of male-to-female transsexuals found that the numbers of neurons in this region were more typical of females.

A third way?

Some people argue that rigid two-gender societies – which insist that every individual be categorised as either a man or a woman – fail to take into account a wider spectrum of gender variance.

There are societies that include multiple gender categories, such as the so-called two-spirit people in Native American tribes. On the Indian subcontinent an estimated 5–6 million people are classified as ‘hijra’, or ‘eunuchs’ (although they have rarely undergone genital surgery). Hijra are usually biologically male or ‘intersex’ and dress as females, but do not see themselves as male or female. Indian passports now include three categories – male, female and eunuch – and allow transgendered individuals who have not had surgery to put male or female on their passport based on their chosen self-identity.

In some Polynesian societies ‘fa’afafine’ are likewise considered to be a ‘third gender’. They are biologically male, but dress and behave in a manner considered typically female. ‘Kathoeys’ (ladyboys) of Thailand fall into a similar category. In Europe intersex/third gender tends not to be recognised in legal terms, except in Germany, where an option of ‘blank’ is given on birth certificates. In 2013 Nils Muižnieks, the Council of Europe Commissioner for Human Rights, urged European governments to review their current legislation with regard to rights for intersex people.

Lead image:

Picture taken at a 2013 rally for transgender equality.

Ted Eytan/Flickr CC BY


About this resource

This resource was first published in ‘How We Look’ in June 2008 and reviewed and updated in November 2014.

Genetics and genomics, Neuroscience, Ecology and environment, Psychology, History
How We Look
Education levels:
16–19, Continuing professional development