Clinical and molecular aspects of androgen insensitivity

Androgen insensitivity describes the inability of cells to respond adequately to androgens. The clinical aspects are well characterized and described in the androgen insensitivity syndrome, where underandrogenization occurs despite normal to high levels of androgens. In 46,XY individuals, this is associated with a variable phenotype ranging from completely female to ambiguous genitalia and infertility in males with gynecomastia. Androgen action is facilitated by a single androgen receptor (AR), whose gene is localized on the X chromosome. However, the identification of mutations in the AR gene in patients with androgen insensitivity is variable, and chances are lower the more subtle the phenotype is. Therefore, other currently unknown mechanisms must be hypothesized to lead to the respective phenotype. The AR is a nuclear transcription factor, acting in concert with an array of only partly known cofactors serving as modulators of target gene transcription. The induced transcription pattern is highly tissue and cell specific, and in some tissues may lead to lasting changes of cell programming. Only one regulated gene APOD has currently been identified to serve as a clinical tool for the diagnosis of androgen insensitivity.