Different aspects of the reciprocal regulatory influence of systems producing the immune and gonadotropin-releasing hormone (GnRH) in pre- and postnatal ontogeny are discussed in this review. GnRH is a neurohormone synthesized by a small population of neurons located in the anterior hypothalamus, which regulates the secretion of gonadotropines in the anterior lobe of the pituitary gland and they finally regulate the synthesis of sex steroids. Particular attention is given to analysis of the data involving the role of thymus peptides and cytokines in GnRH-system regulation in the normal condition and in the case of inflammation development caused by endotoxines in adult animals. The main prospects of the studies involving the influence of proinflammatory cytokines on GnRH-neuron migration and differentiation in prenatal ontogenesis are also discussed.