Sexual development is determined by chromosomes during fertilization. In the early stages of human development, a human embryo has the
precursors of female (paramesonephric or Müllerian ducts) and male (mesonephric ducts or Wolffian) gonads. If a
Y chromosome is lacking, or defective as seen in
Swyer syndrome, the embryo will reabsorb the mesonephric ducts and proceed with paramesonephric ducts, which give rise to ovaries. The Y chromosome contains a sex-determining region called the
SRY gene. Thus, the developmental plan of the embryo is altered only if this gene is present and functional. Mutations affecting the androgen receptor (AR) gene may cause either complete or partial
androgen insensitivity syndrome.
Androgens are a group of hormones which regulate the development and maintenance of male characteristics. Between 8 and 12 weeks, human male fetuses become externally distinct as androgens enlarge the phallus and produce a penis with a urethra and
scrotum. Female pseudohermaphroditism refers to an individual with ovaries and external genitalia resembling those of a male. Male pseudohermaphroditism refers to an individual with testicles and external genitalia resembling those of a female. In some cases, external
sex organs associated with pseudohermaphroditism appear intermediate between a typical
clitoris and
penis. Thus, pseudohermaphroditism is sometimes not identified until
puberty or adulthood.
Persistent Müllerian duct syndrome was considered a form of pseudohermaphroditism, developed through Müllerian-inhibiting factor defects. In such instances, duct derivatives are present in males, including the uterus, fallopian tubes, and upper vagina. ==Management==