Reproductive Use of the GnRH in Cats and Dogs

Gonadotropin-releasing hormone (GnRH) stimulates the pituitary secretion of both follicle-stimulating hormone (FSH) and luteinising hormone (LH), and thus controls the hormonal functions of the ovarium. GnRH analogues have been produced by amino acid substitutions within the native GnRH molecule resulting in a greater potency and a longer duration of effectiveness. Generally, GnRH analogues are used safely for oestrus induction or suppression and provide an advantage over other methods. The GnRH agonists mimic the native GnRH and stimulate the release of gonadotropin with different power from adenohypophysis. Upon the GnRH agonist administration, it causes initially a flare-up effect due to gonadotropin secretion. However, hypogonadotropic hypogonadism occurs about 10-15 days after the administration of agonist. For this purpose, in recent years, GnRH agonist, as often preferred, is safely used for irreversible oestrus induction or suppression, termination of pregnancy, endocrinological diagnosis, urinary incontinence and the treatment of mammary tumour. Antagonists compete successfully with the endogenous GnRH and bind to gonadotrope GnRH receptors. Thus, upon the occupancy of the receptor, they provide blockade and suppress the secretion of gonadotropins. Upon the administration of GnRH antagonists, they rapidly down-regulate the gonadotropin level without flare-up effect and this feature provides an advantage against the agonists. In recent years, although studies on reproduction in female cats and dogs have increased, more research is needed. In the present review, the structure of the GnRH analogues and their current use in cats and dogs are given.