Testicular feminization: a model for testicular descent in mice and men.

The position of the testis was determined in patients and mice with the testicular feminization (TFM) syndrome, to answer the question, do androgens cause testicular descent? In 16 children with complete or partial TFM syndrome with androgen insensitivity, plus two children with a deficiency of androgen secretion, the testes were at or beyond the internal inguinal ring in 35 out of 36 instances. In male mice with TFM, the testes had descended normally to the internal ring by the time of birth but further descent was absent. These observations suggest testicular descent is a two-stage process comprising transabdominal and transinguinal phases. The first phase is not controlled by androgen, and hence is normal in TFM; by contrast the second phase is androgen-dependent, and absent in TFM. It is speculated that the first phase may be regulated by Müllerian Inhibiting Substance, although this is unproven. Because testicular descent in TFM can be separated into two stages, the TFM mouse should prove a useful model for studying the hormonal control of descent of the testis.