Postnatal testicular maldevelopment in unilateral cryptorchidism.

Histomorphometric analysis of semi-thin sections was performed on testicular biopsies of 232 unilaterally cryptorchid testes and 195 of their contralateral descended partners. The results demonstrated a decreased number of germ cells detectable from the first year of life. There was delayed and defective transformation of gonocytes to Ad spermatogonia, which normally is complete at age 6 months, delayed or failed transformation of Ad spermatogonia to primary spermatocytes, which normally commences at age 3 years and decreased numbers of Leydig cells. These abnormalities were present in the unilaterally cryptorchid testes and their contralateral descended partners but they were more severe, of earlier onset and more progressive in the cryptorchid testes. These findings are compatible with the hypothesis that hypogonadotropic hypogonadism is the cause of the increased incidence of infertility seen in unilateral cryptorchidism.