Androgen insensitivity syndrome

Androgen insensitivity syndrome (AIS) affects the normal development of a child's genitals and reproductive organs.

A child born with AIS is genetically male, but their genitals may appear to be female or somewhere between male and female.

AIS is a very rare condition thought to occur in around 1 in 20,000 births.

Early development

In early stage pregnancy, all unborn babies have identical genitals, regardless of their gender.

As a baby grows inside the womb, they develop either male or female genitals, depending on which pair of sex chromosomes they receive from their parents: XX or XY.

Sex chromosomes

Sex chromosomes are a pair of DNA molecules (X or Y) that play a vital role in a baby's sexual development. Females usually have two X chromosomes, and males usually have one X and one Y chromosome.

The presence of a Y chromosome is important for the development of testes and prevents ovaries developing. If there's no Y chromosome, the female reproductive system and genitals will develop.

Read more about male and female sex chromosomes.

What happens in AIS

The testes produce male hormones called androgens, which usually cause male sex organs, such as the penis, to develop.

However, when a person has AIS, the body ignores the androgen or is insensitive to it. Genitals then develop along female lines, and the testes usually remain inside the body.

Read more about the causes of AIS.

Types of AIS

There are two types of AIS, which are determined by the level of insensitivity to androgen. They are:

  • complete androgen insensitivity syndrome (CAIS)  when there is total insensitivity to androgen and a child develops external genitals that are entirely female; most children born with CAIS are raised as girls
  • partial androgen insensitivity syndrome (PAIS)  where there is some sensitivity to androgen; the level of sensitivity will determine how the genitals develop

Depending on a person's level of insensitivity to androgen, they may look almost entirely male, entirely female, or have both male and female characteristics.

Children with PAIS can be brought up either as girls or boys; this is dependent on investigations and discussions carried out with the specialist team after their birth.

Read more about the symptoms and grading system used for AIS.

Diagnosing AIS

PAIS is usually diagnosed at birth because the genitals appear different.

Diagnosing CAIS can be more difficult because female genitalia usually looks normal.

Many children with CAIS are diagnosed early in life, when their testes cause hernias. The testes are discovered when the hernias are operated on.

In other cases, CAIS may not be diagnosed until puberty, when a girl's periods don't start and she has a lack of pubic and underarm hair. Breast development tends to be normal.

Read more about how AIS is diagnosed.

Treating AIS

A child with AIS should be offered psychological support. 

When a child with AIS is young, counselling isn't always needed because their condition is completely natural to them. However, counselling will be needed as the child gets older.

It's recommended that children with AIS fully understand their condition before they reach puberty, so they're aware of the changes they may experience and the differences between them and their friends.

Children with PAIS may need to take hormone supplements. Girls with PAIS who've had their testes removed will need to take oestrogen (a female sex hormone), to encourage female development during puberty and maintain secondary sexual characteristics in adulthood. It's not clear whether androgen supplementation is beneficial.

Boys with PAIS may need to take androgens (male sex hormones) to encourage certain male characteristics, such as facial hair growth and the deepening of their voice.

Women with CAIS who've gone through puberty and had their testes removed will need to take oestrogen, to prevent them getting menopausal symptoms and developing weak bones (osteoporosis).

Read more about how AIS is treated.


Most people with AIS are able to lead normal lives after receiving the appropriate care and support. AIS doesn't reduce life expectancy.

Support groups, such as the Androgen Insensitivity Syndrome Support Group (AISSG) and DSD (Differences of Sex Development) families, provide help and support to young people, adults and families affected by AIS.

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