The UIBC, which represents the capacity of TF that has not yet bound to iron, was markedly decreased in the young iron overload group (235.33 ± 67.14 μg/dL) compared with the young control group (339.54 ± 16.43 μg/dL, p < 0.05) and significantly decreased in the old iron overload group (199.86 ± 28.55 μg/dL) compared with the old control group (402.97 ± 54.39 μg/dL, p < 0.001) (Figure 1C). Here, TF is linked to Tangier disease.