The production of gametes is induced in both male and female mammals by the same two hormones: follicle-stimulating hormone (FSH) and luteinizing hormone (LH). The production of these in turn is induced by a single releasing hormone, gonadotropin-releasing hormone (GnRH), which has been the focus of most of the research into immunocontraception against gamete production. GnRH is secreted by the hypothalamus in pulses and travels to the anterior pituitary gland through a portal venous system. There it stimulates the production of FSH and LH. FSH and LH travel through the general circulatory system and stimulate the functioning of the gonads, including the production of gametes and the secretion of sex steroid hormones. Immunity against GnRH thus lessens FSH and LH production which in turn attenuates gamete production and secondary sexual characteristics.
While GnRH immunity has been known to have contraceptive effects for some time, only in the 2000s has it been used to develop several commercial vaccines. Equity® Oestrus Control is a GnRH vaccine marketed for use in non-breeding domestic horses. Repro-Bloc is GnRH vaccine marketed for use in domestic animals in general. Improvac® is a GnRH vaccine marketed for use in pigs not as a contraceptive, but as an alternative to physical castration for the control of boar taint. Unlike the other products which are marketed for use in domestic animals, GonaCon™ is a GnRH vaccine being developed as an United States Department of Agriculture initiative for use for control of wildlife, specifically deer.