[Pathogenesis of undescended testis].

Testes descend to the scrotum normally before birth. Testis-derived testosterone and insulin-like peptide 3 (INSL3) regulate the descent. Cryptorchid testis remains too high or in an abnormal location, which prevents its normal function. The incidence of cryptorchidism varies greatly: 1 to 8% in full-term newborn boys, and 1 to 2% at three months of age. Spontaneous descent can occur during the first three months. Defective androgen action can cause cryptorchidism, but usually the etiology remains unknown. Several factors (environment, genes and lifestyle) contribute to the risk of cryptorchidism. Acquired cryptorchidism also occurs during childhood. The recommended treatment of cryptorchidism is surgical orchidopexy.