The hypothalamic-pituitary-gonadal (HPG) axis orchestrates reproductive function in vertebrates, with gonadotropin-releasing hormone (GnRH) and its receptor (GnRH-R) serving as key regulators in this endocrine cascade. In teleost fishes, including economically and ecologically significant species such as Heteropneustes fossilis (Singhi), the GnRH-GnRH-R system plays a vital role in initiating and maintaining reproductive processes. This review presents a comprehensive analysis of current research on the structure, expression, and function of GnRH receptors in H. fossilis, with particular emphasis on their expression in the pituitary gland. Recent studies have revealed tissue-specific and seasonally regulated expression patterns of GnRH-R mRNA in H. fossilis, aligning with the species’ reproductive cycle. The activation of GnRH-R in the pituitary stimulates the synthesis and secretion of gonadotropins luteinizing hormone (LH) and follicle-stimulating hormone (FSH) which are essential for gametogenesis and gonadal maturation. Comparative genomic and phylogenetic analyses further indicate both conservation and species-specific adaptations in the GnRH-R gene among teleosts. This review also highlights the influence of environmental factors such as photoperiod, temperature, and stress on the modulation of GnRH-R expression and activity in H. fossilis. These insights are particularly relevant for understanding the reproductive seasonality of the species and for optimizing induced breeding protocols in aquaculture. Moreover, the potential application of molecular tools, such as gene expression profiling and receptor agonists, in enhancing reproductive performance is discussed. By consolidating available knowledge on GnRH-R in H. fossilis, this review provides a framework for further research into reproductive endocrinology in catfish and other freshwater teleosts. The findings not only contribute to basic science but also support the development of biotechnological interventions aimed at improving fish breeding and conservation strategies.
