Androgen insensitivity syndrome

Androgen insensitivity syndrome is a condition in which cells respond partly or not at all to androgens, usually because of changes affecting the androgen receptor. It occurs in people with one X chromosome and a Y chromosome and has complete, partial, and mild forms.

Androgen receptor: A protein that binds androgens and regulates gene activity in responsive cells. Changes in this receptor are the usual cause of reduced androgen response.
Androgen: A class of hormones that includes testosterone and dihydrotestosterone and supports male-typical development. Androgen insensitivity is specifically a reduced cellular response to this hormone class.
Genetic testing: Laboratory analysis used to identify changes in a person’s DNA. Testing the androgen receptor gene can confirm many suspected cases.
Complete androgen insensitivity syndrome: A form of androgen insensitivity syndrome in which tissues show little or no response to androgens. It contrasts with partial forms through the near absence of androgen-dependent traits.
Testosterone: A steroid hormone that supports development and maintenance of reproductive tissues and other traits. Testosterone is present, but affected cells respond inadequately to its signals.
Sex chromosome: A chromosome involved in biological sex development; humans typically have X and Y chromosomes. The condition is associated with a Y chromosome and a variant on the X chromosome.
Karyotype: An organized display of an individual's chromosomes used to assess their number and structure. Chromosome analysis can identify the typical 46,XY pattern associated with the syndrome.
5-alpha-reductase deficiency: An inherited condition in which impaired conversion of testosterone to dihydrotestosterone affects development. It can resemble partial androgen insensitivity, but the defect is hormone conversion rather than receptor response.
Dihydrotestosterone: An androgen made from testosterone that strongly activates the androgen receptor. Its signaling helps explain why external genital development varies with receptor function.
SRY: A gene on the Y chromosome that usually initiates testis development in embryos. Testis development can proceed even when later androgen signaling is impaired.

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