The first known step of sexual differentiation of a normal<unk>  fetus is the development of testes. The early stages of testicular formation in the second month of gestation requires the action of several genes, one of the earliest and most important of which is SRY: the sex-determining region of the Y chromosome. When such a gene is defective, the indifferent gonads fail to differentiate into testes in an<unk>  fetus. Without testes, no testosterone or antimüllerian hormone (AMH) is produced. Without testosterone, the wolffian ducts fail to develop, so no internal male organs are formed. Also, the lack of testosterone means that no dihydrotestosterone is formed and consequently the external genitalia fail to virilize, resulting in normal female genitalia. Without AMH, the Müllerian ducts develop into normal internal female organs (uterus, fallopian tubes, cervix, vagina).
XY gonadal dysgenesis
XX gonadal dysgenesis
Thyroid dysgenesis
Complete androgen insensitivity syndrome
Mild androgen insensitivity syndrome
Gonadotropin-releasing hormone insensitivity
Gonadal dysgenesis
Müllerian agenesis