Hyperthermia and human spermatogenesis: enhancement of the inhibitory effect obtained by 'artificial cryptorchidism'.

Decreased sperm count and motility were observed in men after induction of local testicular hyperthermia by raising the testicles into the inguinal canal during the day in adult volunteers. A similar technique in which the testicles were better maintained in the inguinal canal resulted in more marked suppression of spermatogenesis. As assessed by the total motile sperm count, the mean inhibitory effect of hyperthermia was at least 97% after 2 months using this technique. This effect of 'artificial cryptorchidism' may be of practical interest in the manipulation of male fertility.