Androgen insensitivity syndrome (AIS) is when a person who is genetically male (who has one X and one Y chromosome) is resistant to male hormones (called androgens). As a result, the person has some or all of the physical traits of a woman, but the genetic makeup of a man.
Causes, incidence, and risk factors
Androgen insensitivity syndrome (AIS) is caused by genetic defects on the X chromosome. These defects make the body unable to respond to the hormones that produce a male appearance.
The syndrome is divided into two main categories:
Complete androgen insensitivity prevents the penis and other male body parts from developing. At birth, the child looks like a girl. The complete form of the syndrome occurs in as many as 1 in 20,000 live births.
How many male traits people have differ in incomplete AIS.
Incomplete AIS can include other disorders, such as:
Failure of one or both testes to descend into the scrotum after birth
Hypospadias, a condition in which the opening of the urethra is on the underside, instead of at the tip, of the penis
Reifenstein syndrome (also known as Gilbert-Dreyfus syndrome or Lubs syndrome)
Infertile male syndrome is also considered to be part of incomplete AIS.
A person with complete AIS appears to be female but has no uterus, and has very little armpit and pubic hair. At puberty, female sex characteristics (such as breasts) develop. However, the person does not menstruate and become fertile.
Persons with incomplete AIS may have both male and female physical characteristics. Many have partial closing of the outer vaginal lips, an enlarged clitoris, and a short vagina.
Testes in the abdomen or other unusual places in the body
Signs and tests
Complete AIS is rarely discovered during childhood. Sometimes, a growth is felt in the abdomen or groin that turns out to be a testicle when it is explored with surgery. Most people with this condition are not diagnosed until they do not get a menstrual period or they have trouble getting pregnant.
Incomplete AIS is often discovered during childhood because the person may have both male and female physical traits.
Tests used to diagnose this condition may include:
Blood work to check levels of testosterone, luteinizing hormone (LH), and follicle-stimulating hormone (FSH)
Genetic testing (karyotyping)
Other blood tests may be done to help tell the difference between AIS and androgen deficiency.
Testicles that are in the wrong place may not be removed until a child finishes growing and goes through puberty. At this time, the testes may be removed because they can develop cancer, just like any undescended testicle.
Estrogen replacement is prescribed after puberty.
Treatment and gender assignment can be a very complex issue, and must be targeted to each individual person.
The outlook for complete AIS is good if the testicle tissue is removed at the right time. The outlook for incomplete AIS depends on the appearance of the genitals.
Psychological and social issues
Calling your health care provider
Call your health care provider if you or your child have signs or symptoms of the syndrome.
Wysolmerski JJ. Insogna KL. The parathyroid glands, hypercalcemia, and hypocalcemia. In: Kronenberg HM, Schlomo M, Polansky KS, Larsen PR, eds. Williams Textbook of Endocrinology. 11th ed. St. Louis, Mo: WB Saunders; 2008:chap 266.
Bringhurst FR, Demay MB, Kronenberg HM. Disorders of mineral metabolism. In: Kronenberg HM, Schlomo M, Polansky KS, Larsen PR, eds. Williams Textbook of Endocrinology. 11th ed. St. Louis, Mo: WB Saunders; 2008:chap 27.
Shehzad Topiwala, MD, Chief Consultant Endocrinologist, Premier Medical Associates, The Villages, FL. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M. Health Solutions, Ebix, Inc.