GDF15 and obesity due to melanocortin 4 receptor deficiency: Growth differentiation factor-15 (GDF-15) is a cytokine belonging to the transforming growth factor-beta (TGF-β) superfamily and plasmatic level is positively associated with the development of several diseases including obesity [1,2], type 2 diabetes (T2D) [3,4], non-alcoholic steatohepatitis (NASH) [5], cardiovascular diseases [6] and various cancers [7,8].