Prepubertal Use of Long-Term GnRH Agonists in Dogs: Current Knowledge and Recommendations

SIMPLE SUMMARY: Delay of puberty is sometimes desired by pet owners and can prevent early occurrence of estrus and unwanted pregnancies. Long-term delay of puberty is possible with GnRH agonists such as deslorelin that can be applied as subcutaneous implants. Many studies have been performed to investigate the best age for implantation, and whether undesired side-effects on body development, height at whither, and behavior may occur. At present, most important appears the age at implantation in that one 4.7 mg deslorelin implant should be inserted s.c. between the 3rd and 4th month of life to prevent a flare-up or induction of estrus. Body development as well as fertility after occurrence of first heat after the end of efficacy were normal. However, long-term effects on joint health, tumor development, immune system, and behavior deserve further investigation. ABSTRACT: The search for an alternative approach of estrus control (induction or suppression) in dogs is an important issue and the use of slow GnRH agonist-releasing implants has been the subject of frequent research in recent years. Studies to date demonstrate that the short- and long-term effects of deslorelin implants applicated at different time points of the prepubertal period are similar to those of adult dogs; however, there are important differences. The age of the prepubertal bitch and the dosage appear to be the main determinants of the response to deslorelin, as well as the individual metabolism of the bitch. Recent studies reported that the deslorelin-mediated long-term delay of puberty does not have negative carry-over effects on subsequent ovarian functionality, serum steroid hormone concentrations, uterine health, and fertility; however, more molecular studies are needed to determine the effects of application time of GnRH agonists on hormone concentrations and peripheral receptor expression. Furthermore, the long-term effects of delay of puberty with deslorelin on joint health, tumor development, the immune system, and social behavior deserve further investigations.