FGF21 and obesity due to melanocortin 4 receptor deficiency: Serum FGF21 levels were also significantly higher in patients with both obesity and type 2 diabetes (29), in mitochondria disease patients with dysfunctional mitochondria (30), in Cushing’s syndrome patients with prolonged and inappropriately high levels of glucocorticoids (31), and in preeclampsia patients with serious cardiovascular complications in pregnancy (32).