These are individuals which are genotypically male with a 46XY karyotype, but phenotypically are female. The condition results from a complete or partial absence of cytoplasmic receptors for testosterone in target tissues. It is an X-linked disorder with an incidence of 1 in 62000 male births.
The feminisation is a consequence of increased testicular secretion of oestradiol and from peripheral conversion of androgens to oestradiol. Serum LH and FSH are elevated as testosterone is ineffective at the hypothalamus.