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Androgen insensitivity syndrome

Androgen insensitivity syndrome (AIS) is a genetic condition that affects the development of the external male genitals and reproductive organs.

Every embryo, whether genetically male (XY) or female (XX), initially has the capacity to develop either a male or female external reproductive system. After a few weeks in an XY foetus, without AIS, male genitals develop under the influence of male hormones (androgens).

In AIS, the foetus has male (XY) sex chromosomes but the X chromosome is either:

  • completely androgen insensitive (CAIS) - when the external genitals take a female form, or
  • partially androgen insensitive (PAIS) when the external genital appearance lies somewhere between male and female.

Individuals with AIS have a functioning Y sex chromosome and male internal sex organs (testes instead of womb, ovaries and fallopian tubes), but a fault on the X sex chromosome that leaves the body completely or partially unable to recognise the androgens produced so the external organs are female or indeterminate.