GnRH immunization and male infertility: immunocontraception potential
Awoniyi, C.A.
Advances in Contraceptive Delivery Systems Cds 10(3-4): 279-290
1994
ISSN/ISBN: 1012-8689 PMID: 12287842 Document Number: 425252
Immunization with gonadotropin-releasing hormone (GnRH) effects relatively long-term azoospermia. Either administration of ample exogenous testosterone or letting the effects of the antibodies diminish naturally results in complete reversibility of the GnRH contraceptive vaccine. In one experiment, fertility was completely restored in all rats 12 months following the cessation of booster injections. Since GnRH immunization suppresses testosterone synthesis, subjects could potentially suffer the undesirable symptoms of hypogonadism, thus necessitating adequate testosterone supplementation. Administration of low dose testosterone treatment to GnRH-immunized rats effectively maintains sexual function and other androgenic characteristics without restoring fertility. Specifically, low dose testosterone delivered by sustained release Silastic implants (2 cm) to laboratory rats reactivates and preserves libido and weights of accessory sex organs while continuing to suppress spermatogenesis. Other researchers obtain similar results by injecting GnRH-immunized rats with testosterone. The rat model not only shows that GnRH immunization/testosterone replacement causes azoospermia without adversely influencing libido, sexual function, and other androgen-dependent processes, but also yields low cost, simplicity, and infrequent administration (i.e., periodic booster injections). An immunological method of inhibiting spermatogenesis combined with administration of exogenous testosterone offers promise as a strategy leading to a convenient, reversible, and effective male contraception.