Androgen insensitivity syndrome
Androgen insensitivity syndrome (AIS) is a difference in sex development involving hormonal resistance due to androgen receptor dysfunction.
| Androgen insensitivity syndrome | |
|---|---|
| AIS results when the function of the androgen receptor (AR) is impaired. The AR protein (pictured) mediates the effects of androgens in the human body. | |
| Specialty | Endocrinology |
It affects 1 in 20,000 to 64,000 XY (karyotypically male) births. The condition results in the partial or complete inability of cells to respond to androgens. This unresponsiveness can impair or prevent the development of male genitals, as well as impairing or preventing the development of male secondary sexual characteristics at puberty. It does not significantly impair female genital or sexual development. The insensitivity to androgens is therefore clinically significant only when it occurs in genetic males, (i.e. individuals with a Y-chromosome, or more specifically, an SRY gene). Clinical phenotypes in these individuals range from a typical male habitus with mild spermatogenic defect or reduced secondary terminal hair, to a full female habitus, despite the presence of a Y-chromosome.
AIS is divided into three categories that are differentiated by the degree of genital masculinization:
- Mild androgen insensitivity syndrome (MAIS) is indicated when the external genitalia are those of a typical male (a penis and a scrotum)
- Partial androgen insensitivity syndrome (PAIS) is indicated when the external genitalia are partially, but not fully, masculinized
- Complete androgen insensitivity syndrome (CAIS) is indicated when the external genitalia are those of a typical female (a vulva)
Androgen insensitivity syndrome is the largest single entity that leads to 46,XY undermasculinized genitalia.
Management of AIS is currently limited to symptomatic management; no method is currently available to correct the malfunctioning androgen receptor proteins produced by AR gene mutations. Areas of management include sex assignment, genitoplasty, gonadectomy to reduce tumor risk, hormone replacement therapy, genetic counseling, and psychological counseling.