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in man and certain animals (horses, dogs), a developmental defect in which during intrauterine development a testis fails to descend to its normal position in the scrotum.
The formation of spermatozoa in an undescended testis may be diminished or absent. In man, unilateral cryptorchidism is usually caused by intra-abdominal adhesions, shortening of the ductus deferens, underdevelopment of the internal spermatic artery, or narrowness of the inguinal canal. Bilateral cryptorchidism is usually associated with disturbances of hormonal balance, insufficiency of gonadotropic hormones, or hereditary biological factors. Cryptorchidism is classified as abdominal or inguinal, according to whether the testis is retained in the abdomen or in the inguinal canal. Often the testis descends into the scrotum by the age of ten or 12. Hence, cryptorchidism is observed in only 0.3 percent of adults but in 2–3 percent of children and prepubescents.
Cryptorchidism is treated in children by hormone therapy (pituitary gonadotropic hormone and androgens), accelerating testicular development. Surgery is indicated if this treatment proves unsuccessful.
V. G. TSOMYK