Androgen insensitivity refers to an inability of the body to respond properly to male sex hormones (androgens) produced during pregnancy. This occurs because of a change (mutation) in a gene involved in the production of the protein inside cells that receives the androgen hormone and instructs the cell in how to use it.
Partial androgen insensitivity syndrome (pais) is part of a spectrum of syndromes that also includes androgen insensitivity syndrome (AIS) and mild androgen insensitivity syndrome (mais). In each case, the development of the reproductive and genital organs of the fetus is affected, as a result of the gene mutation.
During the first 10 weeks of pregnancy, the external anatomy of male and female embryos appears to be identical. The presence or absence of the male sex hormone testosterone determines whether male or female genitalia develop. In partial androgen insensitivity syndrome, the development of the external genitals will be intermediate between male and female (ambiguous genitalia).
Each of these forms of AIS is also a hereditary form of male pseudohermaphroditism, in which the baby is born with testes and possesses both male and female characteristics. The disorder is inherited as an X-linked, recessive trait.
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