Hormonal contraception for men: Limitations
Eberhard Nieschlag
Institute of Reproductive Medicine of the University of
Münster, (WHO Collaboration Centre for Research in Male Reproduction), Münster,
Germany
As opinion polls show, men are ready for hormonal male
contraception and would use an effective preparation if it became generally
available. However, they would prefer a pill over any other mode of application.
Notwithstanding, modalities for male contraception currently under investigation
favour testosterone and gestagen injections or implants of a combination of both
as they provide the constant serum levels required for suppression of
gonadotropins and spermatogenesis. This implies that the contraceptive will not
be self administered, but will rather require medical assistance for initiation
and possibly also for termination. The contraceptive protection provided by a
hormonal male method will have a relatively slow onset as, on average, three
months are required to achieve the necessary azoospermia or at least severe
oligozoospermia. Therefore, use of hormonal male contraception will require
careful planning and will be used preferentially by couples in stable
relationships. Similarly, recovery of spermatogenesis after cessation of
hormonal male contraception is relatively slow requiring 3-6 months to regain
full fertility. Since most clinical trials so far did not exceed one year, it is
unclear whether longer use may result in prolonged recovery phases. Non-
uniformity of suppression of spermatogenesis under a given regimen remains an
important limitation. There are ethnic differences (East Asian men respond
better than Caucasians), but also differences within a population which could
not yet be explained by a mechanism that would allow a rational approach to
counteract it. Until this goal is reached it may be necessary to investigate
whether a volunteer has achieved azoospermia or not, i.e. semen analysis would
be required before contraceptive protection can be guaranteed. These
investigations would complicate the use of a male hormonal contraceptive, but
would be similar to the requirements after vasectomy.