FGF-21 presents a multifaceted metabolic profile as it is involved in adipose tissue lipolysis [8, 9], and hepatic lipid content reduction after SGLT2i treatment [10], but surprisingly patients with obesity and T2DM show higher circulating levels of FGF-21 than expected [11, 12], thus questioning the real contribution of FGF-21 to the overall SGLT2i benefit. The gene discussed is FGF21; the disease is obesity due to melanocortin 4 receptor deficiency.