Fig. 35.Schematic drawing of major pathways involved in the regulation of appetite and satiety. Leptin, a white adipose derived cytokine, circulates in the blood stream and binds to receptors on NPY/AGRP- and -MSH/CART-producing neurons in the hypothalamic arcuate nucleus (ARC) to orchestrate a series of responses mediated by downstream centers including the paraventricular nucleus (PVN) to control thyroid hormone secretion, feeding behavior, and energy conservation, and by lateral hypothalamic (LH) orexin- and MCH-producing neurons to control arousal responses and feeding behavior (not shown). Leptin also binds to receptors in the dorsal vagal complex (DVC) that contribute to modulation of the PVN and/or the ARC. Gut-derived peptides and nutrients also contribute to the regulation of appetite and satiety through effects on the arcuate nucleus or NTS. The orexigenic effect of thyroid hormone may be mediated on the ventromedial nucleus (VMN).