This constitutes a group of disorders in which androgen secretion or action is defective at various stages. The extent and the timing of this dictates the phenotypic appearance. In Klinefelter's syndrome a chromosomal abnormality (usually XXY) is associated with small testes, azoospermia and seminiferous tubular dysgenesis. In embryonic testicular regression gonads are absent, but the presence of ducts derived from the Wolffian system indicates that functioning testes were present at some stage during fetal life and subsequently regressed. In male pseudohermaphroditism the genetic sex is at variance with the phenotypic sex, due to tissue 'resistance' to the action of sex steroids.
