FGF21 and obesity due to melanocortin 4 receptor deficiency: The importance of adiponectin must be viewed within the framework of the body’s key signaling pathways that regulate metabolic equilibrium in the face of obesity and cardiovascular disorders [187], such as the modulation by other adipokines (leptin, resistin, and visfatin, as well as brown adipokines, such as FGF21, IL-6, NRG4, IGF-1, and TNF-α).