TF and Tangier disease: In pathological conditions caused by some diseases, iron overload can result from increased iron intake, increased gastrointestinal absorption (Godbold & McFarland, 2021), and accumulation of non-heme iron through heme degradation (Fang et al., 2019), etc. When the body is in a pathological condition of iron overload, the capacity of plasma transferrin to bind iron is saturated, leading to the accumulation of non-transferrin bound iron (Brissot et al., 2012).