Although the level of FGF21 and maximum serum ferritin within 5 years were significantly higher in thalassemia patients with MCI than normal cognitive function, we found that there was no significant correlation between the level of FGF21 and either serum ferritin or maximum serum ferritin within 5 years (Supplementary Fig. 3). This evidence concerns the gene FGF21 and thalassemia.