Definition of Androgen insensitivity syndrome:

Androgen insensitivity syndrome (AIS) is when a person who is genetically male (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 characteristics of a woman, despite having the genetic makeup of a man.

Causes, incidence, and risk factors:

Androgen insensitivity syndrome (AIS) is caused by various genetic defects on the X chromosome that make the body unable to respond to the hormones responsible for the male appearance.

The syndrome is divided into two main categories:

• Complete AIS
• Incomplete AIS

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

The degree of sexual ambiguity varies widely in persons with incomplete AIS. Incomplete AIS can include other disorders such as Reifenstein syndrome (also known as Gilbert-Dreyfus syndrome or Lubs syndrome), which is associated with breast development in men, failure of one or both testes to descend into the scrotum after birth, and hypospadias, a condition where the opening of the urethra is on the underside, rather than at the tip, of the penis.

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