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Androgen insensitivity syndrome

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Androgen insensitivity syndrome

Definition:

Androgen insensitivity syndrome (AIS) is when a person has one X and one Y sex chromosome (making them genetically male), but is resistant to androgens (male hormones). As a result, the individual has some or all of the physical characteristics of a woman, despite having the genetic makeup of a man.

The syndrome is divided into two main categories: complete and incomplete. Complete AIS results in someone who looks outwardly female. In the incomplete AIS syndrome, the degree of sexual ambiguity varies widely from individual to individual.

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Alternative Names:

Testicular feminization

Causes, incidence, and risk factors:

The syndrome is caused by various genetic mutations on the X chromosome. The mutations make a developing male baby unable to respond to androgens. (Androgens are responsible for male physical characteristics.)

If the androgen insensitivity is complete, this prevents the development of the penis and other male body parts. The child is born appearing to be a girl. The complete form of the syndrome occurs in as many as 1 in 20,000 live births.

Different degrees of androgen resistance can result in a wide variety of outward symptoms. Incomplete AIS can include other disorders, such as Reifenstein's syndrome (also known as Gilbert-Dreyfus syndrome or Lubs syndrome), which is associated with hypospadias (where the opening of the urethra is on the underside, rather than at the tip, of the penis), gynecomastia (breast development in men), and cryptorchidism (when one or both testes fail to descend into the scrotum after birth).

Also included in the broad category of incomplete AIS is infertile male syndrome, which is sometimes due to an androgen receptor disorder.

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