Pathogenesis: Development of the Female Genital Tract

Sexual differentiation is governed by the presence or absence of testis-determining factor located on the Y chromosome. In an embryo in which testis-determining factor is expressed, the undifferentiated gonads will develop into testes, producing anti-müllerian hormone and testosterone. Anti-müllerian hormone induces degeneration of the paramesonephric ducts. Testosterone stimulates the mesonephric ducts to develop into male internal genitals. In target tissues, testosterone is converted into dihydrotestosterone which promotes the urogenital sinus to differentiate into male external genitals. In the absence of a Y chromosome and testis-determining factor, the undifferentiated gonads will develop into ovaries. Consequently, no anti-müllerian hormone is produced and the paramesonephric ducts develop into female internal genitals. In the absence of dihydrotestosterone, female external genitals are formed from the urogenital sinus. Environmental and (epi)genetic factors may affect the embryonic and fetal genital organ differentiation and thus render a woman prone to endometriosis in adult life.