Increased FGF21 plasma levels in individuals with obesity, insulin resistance, MASLD and T2DM (Zhang et al., 2008; Ďurovcová et al., 2010; Dushay et al., 2010; Cheng et al., 2011)Treatment with FGF21 analog improves dyslipidemia, decreases body weight and improves fasting insulin levels in patients with T2DM and obesity (Gaich et al., 2013). The gene discussed is FGF21; the disease is obesity due to melanocortin 4 receptor deficiency.