[Cryptorchidism: pathogenesis and histology].

An impairment of the hypothalamopituitarygonadal axis was found to be the main cause of undescended testicles in 80 per cent of patients. Basing himself on personal observation, the author develops the theory that the mechanism of testicular descent is the stimulation by GnRH of the pituitary gland to release gonadotrophins, which in turn stimulate the interstitial cells to secrete testosterone. High local testosterone concentration fosters the development of the differentiating portion of the mesonephric duct into the epididymis. The epididymis induces descent by pushing rather than pulling the testis into the scrotal position. Any interference with this mechanism during the embryonal life leads to cryptorchid testes, which, in the vast majority of cases are localized at the external inguinal ring. The earlier the scrotal position is reached, the greater the chances of subsequent fertility.