FGF21 and obesity due to melanocortin 4 receptor deficiency: Interestingly, FGF-21 levels are also augmented during metabolic diseases such as obesity and type 2 diabetes have increased concentrations.23–25 It has been previously reported that FGF-19 and FGF-21 levels are augmented in PCOS; however, there are also some reports that FGF-19 and FGF-21 levels are unchanged.26–28 In our population, FGF-19 levels were unchanged in the fasted state, in the normal weighted and obese background (Fig. 3A).