Update on Male Hormonal Contraception: Is the Vasectomy in Jeopardy?

GJ Manetti and SC Honig

Disclosures

Int J Impot Res. 2010;22(3):159-170. 

In This Article

GnRH/Gonadotropin Vaccines

Immunomodulation of the reproductive system of animals has been under investigation for many years in the area of fertility control in animals such as rabbits, mice, cattle and subhuman primates for many years. The ideal target for a male contraceptive vaccine remains an interesting area of research that has undergone significant advances due to our improved understanding of gonadotropin feedback mechanism. As seen in Figure 1, as GnRH stimulates secretion of gonadotropic hormones, it is logical that the immunoneutralization of GnRH would prevent endogenous GnRH from binding to its receptors and cause gonadal atrophy in adults, such as sprematogenic arrest and libido loss.[94] Several attempts have been made to couple mammalian GnRH, a nonimmunogenic peptide, to carrier proteins such as tetanus and diphtheria toxoids to enhance the bioefficacy of the antibodies produced.[95] Anti-GnRH vaccines have been tested for control of prostate cancers in India, in hopes of cutting off androgen support to prostate cancer cells.[96] Although there have been reports of contraceptive efficacy in male dogs, there have been no successful structured studies in male nonhuman primates that have carefully evaluated such a contraceptive vaccine.[95]

Other possible vaccine targets include gonadotropins and gonadotropin receptors. Human FSH and ovine FSH are the two such candidate antigens. Attempts were made to use hFSH linked to cholera toxin and interleukin to produce effective antibodies. The immunization using hFSH caused a 75–100% decrease in sperm counts in the ejaculate. The fertility of male monkeys after hFSH immunization was significantly reduced, as described as loss in spermatozoa ability to penetrating hamster ova assay.[95] Even though FSH-based vaccines may not lead to azoospermia, there seems to be increasing evidence that a reduction in the quality of sperm combined with oligospermia may represent a reasonable marker for male contraception as a measure of infertility. Furthermore, using FSH protein fragments instead of GnRH- or LH-based vaccines does not require exogenous testosterone supplementation to maintain accessory gland function and libido.[95] Periodic vaccination as a method for male contraception represents a promising area of research and continues to be refined through the use of better adjuvant compounds.

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