Androgen Insensitivity Syndrome (AIS)

What is androgen insensitivity syndrome (AIS)?

Androgen insensitivity syndrome (AIS) is a rare, inherited condition in which the body cannot respond normally to androgens. Androgens are the group of hormones, including testosterone, that usually direct the body to develop male physical features. A person with AIS has one X chromosome and one Y chromosome (the usual male pattern, written as 46,XY) and produces testosterone, often in normal or even higher-than-usual amounts. The problem lies with the androgen receptor, the protein inside cells that detects and responds to these hormones. When the receptor works poorly or not at all, the hormone signal is partly or completely ignored, and development follows a different path.

Doctors group AIS into three forms based on how much the receptor still works:

• Complete androgen insensitivity syndrome (CAIS): the body does not respond to androgens at all. The person is born with typical female external genitals and is usually raised as a girl.
• Partial androgen insensitivity syndrome (PAIS): the body responds only partly. Genital appearance at birth can range widely and may not be clearly male or female.
• Mild androgen insensitivity syndrome (MAIS): the body responds almost normally. External genitals appear male, and the condition may only be noticed later because of infertility or breast growth.

AIS belongs to a broader group of conditions sometimes called differences (or disorders) of sex development, meaning conditions where chromosomes, gonads (testes or ovaries), or genitals develop in a way that differs from the usual pattern. AIS is not a disease of the mind, and it does not affect intelligence or general health in itself. Many people with AIS live long, healthy lives, though most will need some medical support, especially around puberty and fertility.

Androgen insensitivity syndrome (AIS) symptoms

Androgen insensitivity syndrome (AIS) symptoms depend heavily on the type. Because the signs differ so much, the condition may be recognized in infancy, in the teenage years, or occasionally only in adulthood.

Complete AIS (CAIS) is often not suspected at birth because the baby looks like a typical girl. Common features include:

• A lump or swelling in the groin in a baby girl, which may be an inguinal hernia (tissue pushing through a weak spot in the abdominal wall) containing a testis.
• No menstrual periods by the mid-teens, even though breasts develop normally.
• Little or no pubic and underarm hair after puberty.
• A vagina that is shorter than usual or ends in a closed pouch.
• No uterus (womb) and no ovaries, seen on imaging.
• Testes located inside the abdomen or groin rather than in a scrotum.
• Height that is often toward the taller end of the typical female range.

Partial AIS (PAIS) is usually recognized at birth because the genitals appear atypical. Possible features include:

• A small penis (micropenis) or an enlarged clitoris.
• Hypospadias, where the opening of the urethra (the tube that carries urine) is on the underside of the penis rather than the tip.
• A scrotum that is partly divided or resembles labia.
• Undescended testes (testes that have not moved down into the scrotum).
• Breast development (gynecomastia) in adolescent boys.
• Reduced facial and body hair and a higher-pitched voice at puberty.

Mild AIS (MAIS) is the most subtle. A person may have typical male genitals and only notice difficulty conceiving a child, breast enlargement during puberty, or sparse body hair. Some people with MAIS are never diagnosed.

Breast development in CAIS happens because the body converts some of its testosterone into estrogen, the main female hormone, and the body does respond to estrogen. This is also why periods do not occur: without a uterus there is no lining to shed, even though other signs of puberty appear on time.

Causes and risk factors

The androgen insensitivity syndrome (AIS) causes are genetic. Almost all cases are due to a change (mutation) in the AR gene, which carries the instructions for building the androgen receptor. The AR gene sits on the X chromosome. Because people with a 46,XY chromosome pattern have only one X chromosome, a single altered copy of the gene is enough to cause the condition. This inheritance pattern is called X-linked recessive.

In many families the altered gene is passed down from a mother who carries it. A carrier mother has two X chromosomes, one with the altered gene and one working copy, so she usually has no symptoms herself, although some carriers have slightly reduced pubic or underarm hair. Each child of a carrier mother who has a Y chromosome has a one-in-two chance of inheriting the altered gene and having AIS. Each child with two X chromosomes has a one-in-two chance of being a carrier. In a meaningful share of cases, however, the mutation is new and arises for the first time in the affected child, with no family history.

Risk factors for AIS are therefore limited to inheritance:

• A mother known to carry an AR gene mutation.
• A sibling, maternal uncle, or maternal cousin with AIS.
• A family history of unexplained infertility, absent periods, or groin hernias in girls.

Nothing a parent does or does not do during pregnancy causes AIS. It is not related to diet, medicines, infections, or lifestyle, and there is no way to prevent it once conception has occurred.

Androgen insensitivity syndrome (AIS) diagnosis

Androgen insensitivity syndrome (AIS) diagnosis usually involves a combination of a physical examination, hormone blood tests, imaging, and genetic testing. Because the picture varies so much, doctors often work through the possibilities step by step rather than relying on a single test.

• Physical examination: the doctor looks at the genitals, checks for hernias or lumps in the groin, and, in adolescents, notes patterns of breast development and body hair.
• Karyotype: a blood test that examines the chromosomes. In AIS it shows a 46,XY pattern. This is often the test that first raises suspicion, for example in a girl with absent periods or a groin hernia.
• Hormone tests: blood levels of testosterone, luteinizing hormone (LH, a brain hormone that stimulates the testes), and anti-Müllerian hormone (AMH, a marker of testicular tissue). In AIS, testosterone and LH are usually normal or high for a 46,XY person, which helps distinguish it from conditions where the testes cannot make testosterone.
• Imaging: an ultrasound or MRI (magnetic resonance imaging, a detailed scan that uses magnets rather than radiation) of the pelvis and abdomen to look for a uterus and to locate the gonads.
• Genetic testing of the AR gene: confirms the diagnosis in most cases by identifying the specific mutation. It also allows testing of relatives who may be carriers.
• Stimulation tests: in infants and young children, a short course of a hormone called hCG may be given to see how the testes respond, which can help separate AIS from other causes of atypical genitals.

Occasionally AIS is suspected before birth, when a prenatal chromosome test shows 46,XY but an ultrasound suggests female genitals. In these cases the diagnosis is confirmed after birth. When AIS is diagnosed in a baby with atypical genitals, doctors usually recommend that decisions about sex of rearing be made carefully with the family, with support from a team that includes endocrinology (hormone specialists), genetics, urology or gynecology, and psychology.

Androgen insensitivity syndrome (AIS) treatment options

There is no treatment that repairs the androgen receptor, so care focuses on health, wellbeing, and supporting the person’s development and choices. Androgen insensitivity syndrome (AIS) treatment options are best managed by a multidisciplinary team, and the plan changes across a person’s life. The following are the main areas that a care team typically discusses.

Observation and monitoring. Many aspects of AIS do not need immediate action. Growth, puberty, bone health, and the gonads are followed over time. The testes in CAIS produce hormones that drive natural puberty, so many teams now suggest leaving them in place at least until puberty is complete, provided they can be monitored.

Management of the gonads. Testes that remain inside the body carry a risk of developing tumors, and this risk appears to rise after puberty and to be higher in PAIS than in CAIS. Options include regular monitoring with imaging, a biopsy (taking a small tissue sample), or surgical removal of the gonads (gonadectomy). The timing of removal is an area of ongoing discussion among specialists, and current practice increasingly involves waiting until the person is old enough to take part in the decision, where safe to do so.

Hormone replacement. If the gonads are removed, or if puberty does not progress on its own, hormone replacement is needed. For people living as women this is usually estrogen, which supports breast development, bone strength, and general wellbeing. For people living as men, testosterone may be given, sometimes in higher-than-usual doses in PAIS or MAIS because the body responds weakly. Hormone replacement is usually long term and is adjusted by the doctor over time.

Vaginal dilation. Many women with CAIS have a shorter vagina. In most cases this can be lengthened without surgery by gently stretching the tissue with graded dilators over several months. This is generally started when the person feels ready and is offered before any surgical option.

Surgery. Beyond gonadectomy, surgery may include repair of an inguinal hernia in infancy, correction of hypospadias, or, less often, procedures to lengthen the vagina if dilation has not been successful. Surgery to alter the appearance of the genitals in young children is now approached with great caution in many centers, and families are usually encouraged to delay procedures that are not medically necessary until the person can consent.

Psychological support. Counseling for the person and their family is considered a core part of care, not an add-on. It supports understanding of the diagnosis, decisions about disclosure, questions of identity, and relationships.

Fertility counseling. People with CAIS and most people with PAIS cannot produce eggs or sperm. Some individuals with MAIS have reduced sperm production and may be helped by fertility treatments. For those who wish to build a family, options may include adoption or, where legally available, assisted reproduction using donor eggs and a gestational carrier. Specialists in the IVF & Reproductive Health unit can explain what is realistic in an individual situation. At Acibadem, AIS is generally managed jointly by pediatric or adult endocrinology, genetics, urology or gynecology, and psychology services.

Living with androgen insensitivity syndrome (AIS) and outlook

The long-term outlook for people with AIS is generally good. Life expectancy is not thought to be reduced by the condition itself, and most people have normal intelligence, physical fitness, and overall health. The main ongoing medical needs are hormone replacement if the gonads have been removed, protection of bone density, and periodic follow-up of the gonads if they remain in place.

Bone health deserves particular attention. Because the bones of a person with AIS do not respond to androgens, and because estrogen levels may fall after gonadectomy or with missed hormone doses, there is a tendency toward lower bone density. Regular weight-bearing exercise, adequate calcium and vitamin D, avoiding smoking, and taking prescribed hormones consistently are the usual recommendations. Your doctor may suggest a bone density scan at intervals.

Gender identity in AIS most often matches the sex in which a person is raised, particularly in CAIS, where the large majority of individuals identify as women. In PAIS the picture is more varied, which is one reason for careful, unhurried decision-making in childhood. Whatever a person’s identity, honest, age-appropriate information from an early age is widely regarded as better for wellbeing than secrecy, which in the past caused lasting distress for many.

Learning about infertility can be one of the hardest parts of the diagnosis. Support from psychologists and from peer groups of other people with AIS often helps, and many people go on to form families in a variety of ways. Sexual function is usually satisfactory, especially when vaginal dilation, if needed, is completed on the person’s own timeline.

Frequently asked questions

What is androgen insensitivity syndrome (AIS) in simple terms?

AIS is a genetic condition in which a person with XY chromosomes has cells that cannot properly respond to male hormones called androgens. Testosterone is produced, but the body largely ignores it, so development follows a female or partly female pattern depending on how much the hormone receptor still works.

Is androgen insensitivity syndrome (AIS) the same as being intersex?

AIS is one of the conditions included under the umbrella terms intersex or differences of sex development. Some people with AIS use the word intersex to describe themselves and others do not; the choice is personal, and both are considered acceptable.

Can a woman with complete AIS have children?

Women with CAIS do not have a uterus or ovaries, so they cannot become pregnant or produce eggs. Some choose adoption, and in places where it is legally permitted, some pursue assisted reproduction using donor eggs and a gestational carrier. A reproductive medicine specialist can discuss the options available in a specific country.

Do the testes have to be removed in androgen insensitivity syndrome (AIS)?

Not necessarily, and not always right away. Internal testes carry a risk of tumors that appears to increase after puberty, so doctors either monitor them with imaging or recommend removal. Many teams now favor waiting until after puberty and involving the person in the decision, although the approach varies with the type of AIS and individual circumstances.

How is androgen insensitivity syndrome (AIS) diagnosed if the baby looks like a girl?

CAIS is often found when a baby girl has a groin hernia that turns out to contain a testis, or when a teenage girl has not started periods despite normal breast development. A karyotype showing 46,XY, hormone tests, pelvic imaging, and AR gene testing then confirm the diagnosis.

Is there a cure for androgen insensitivity syndrome (AIS)?

No. The altered androgen receptor cannot currently be repaired. Treatment focuses on hormone replacement when needed, careful management of the gonads, support for sexual and reproductive health, and psychological care, which together allow most people to live healthy lives.

Should other family members be tested?

Often, yes. Because AIS is usually passed down through carrier mothers, genetic counseling and testing may be offered to the mother, sisters, and maternal relatives so they understand their own chances of being carriers or of having an affected child.

When to see a doctor

Many aspects of AIS are handled through planned follow-up, but some situations should prompt a medical review without delay. Seek medical advice if you or your child experience any of the following:

• A new or enlarging lump or swelling in the groin of an infant or child, especially a girl.
• Sudden, severe pain or swelling in the groin or lower abdomen, which could indicate a twisted or trapped gonad or hernia and may need urgent treatment.
• No menstrual periods by age 15 to 16, particularly if breast development has occurred.
• Unexpected breast growth in an adolescent boy, or puberty that stalls or does not start.
• Difficulty passing urine, a urethral opening that is not at the tip of the penis, or testes that cannot be felt in the scrotum.
• Hot flashes, low mood, fatigue, or bone pain after gonadectomy, which may suggest hormone doses need adjusting.
• Persistent feelings of distress, anxiety, or hopelessness related to the diagnosis; mental health support is part of standard AIS care.

If you have a family history of AIS and are planning a pregnancy, a genetics consultation before conception can clarify the chances of passing on the condition and the options available.