Gonadotropin releasing hormone (GnRH) is the body’s “master hormone,” which controls reproductive processes in both males and females and across mammalian species. As with certain immunological approaches to fertility control, gonadotropin releasing hormone (GnRH) agonists and antagonists target this “master hormone.” GnRH agonists and antagonists work very differently, however, from GnRH immunocontraceptive vaccines.

An effective GnRH agonist mimics the effect of the GnRH that’s produced naturally by a dog’s body, binding to and causing down-regulation (suppressed response) of the GnRH receptors in the pituitary gland. GnRH must be “seen” through these receptors in the pituitary cells to have a hormonal effect; consequently, the continuous administration of a GnRH agonist suppresses the effect of GnRH. This, in turn, suppresses both fertility and hormone-driven sexual behaviors. In order for a GnRH agonist to have effect, it must be consistently administered. For cats and dogs, the best way to do this is with a long-lasting implant.

Suprelorin® (deslorelin acetate) is a GnRH agonist approved and available in multiple countries for minimum 6- or 12-month contraception of male dogs, depending on implant size. Suprelorin has also been studied in female dogs, as well as in cats of both sexes. It has also been used for over 15 years to prevent fertility in diverse mammalian species, including wild canids and felids, across more than 100 zoos as part of a long-running study. Males and females have both been treated with the product. Our Suprelorin webpage has more detailed product information.

GnRH antagonists prevent fertility by blocking GnRH receptors on the pituitary cells; they do not elicit the initial flare sometimes seen with GnRH agonists. While this is an advantage, other factors, such as cost, could make them less attractive than GnRH agonists. Overall, there has been limited research regarding GnRH antagonists in cats and dogs.

ACC&D has published a number of resources with more detailed information on GnRH agonists/antagonists and Suprelorin specifically. For more information on this approach to fertility control for dogs and cats: