Residual sperm function in oligozoospermia induced by testosterone enanthate administered as a potential steroid male contraceptive

To investigate the fertility of men who remain oligozoospermic despite sex steroid suppression, the in‐vitro fertilizing capacity of residual spermatozoa was assessed in 30 men receiving intramuscular testosterone enanthate (TE). Spermatozoa were prepared by either Percoll or repetitive centrifugation/washing. Although the mean (± SEM) pretreatment zona‐free hamster oocyte penetration (HOP) rates were similar (59.4 ± 10.1 and 63.8 ± 10.8%), following the induction of oligozoospermia the Percoll‐prepared spermatozoa exhibited a penetration rate (26.9 ± 10.2%) which was markedly greater than that obtained for sperm prepared by repetitive washing (0 ± 0%). In addition, the partners of two men exhibiting a HOP test with Percoll‐prepared spermatozoa, conceived despite a sperm concentration of 3 × 10⁶ml^‐1 and a negative HOP test with spermatozoa prepared by repetitive washing. These results suggest that Percoll preparation optimizes the assessment of in‐vitro sperm function and that the fertility of men with TE‐induced severe oligozoospermia is suppressed but not abolished.