Metabolic Regulation by the Hypothalamic Neuropeptide, Gonadotropin-Inhibitory Hormone at Both the Central and Peripheral Levels

Gonadotropin-inhibitory hormone (GnIH) is well-established as a negative regulator of reproductive physiology and behavior across vertebrates, acting on the hypothalamic–pituitary–gonadal (HPG) axis; however, recent data have also demonstrated its involvement in the control of metabolic processes. GnIH neurons and fibers have been identified in hypothalamic regions associated with feeding behavior and energy homeostasis, with GnIH receptors being expressed throughout the hypothalamus. GnIH does not act alone in the hypothalamus, but rather interacts with the melanocortin system, as well as with other neuropeptides. GnIH and its receptors are also expressed in peripheral tissues involved in important metabolic functions. Therefore, the local action of GnIH in peripheral organs, including the pancreas, gastrointestinal tract, gonad, and adipose tissue, is also suggested. This review aims to provide a comprehensive summary of the emerging role of GnIH in metabolic regulation at both the central and peripheral levels.