Regarding undescended testis, which is the first step to be affected by the testis not having descended into the scrotum?A. Neonatal gonocyte
The transition from neonatal gonocyte to adult dark spermatogonia takes place at 3–12 months in humans. Between the first and fourth years of life the spermatogonia differentiate into B-spermatogonia, and then primary spermatocytes. These then remain quiescent until puberty triggers spermatogenesis. The transformation of the neonatal gonocyte into the adult dark spermatogonia appears to be a crucial stage. It seems to be dependent on the environment of these cells being at 33°C. Failure of the testicle to descend into the scrotum keeps the testis at 37°C and so adversely affects this stage. Transformation from neonatal gonocyte to adult dark spermatogonia includes a reduction in the number of these cells probably reflecting apoptosis of abnormal cells. Failure of the testicle to descend by this stage will result in reduced sperm production but also less removal of abnormal cells probably contributing to increased risk of subsequent malignant transformation. Recognition that this stage takes place quite early has resulted in the British Association of Paediatric Urologist recommending in 2011 earlier orchidopexy. Ideally orchidopexy should be performed between 3–6 months; however, 6–12 months is acceptable.