Nature of nontransferrin‐bound iron

Nontransferrin-bound iron is now recognized to exist by many workers. It is present in the serum of patients suffering from a wide range of disease states and may be induced by certain therapeutic treatments. The chemical nature of this iron pool is unknown but almost certainly it is a multicomponent pool including a considerable proportion of protein-bound iron. Methods are required to separate and quantify these different components. The biological properties of the individual isoforms need to be established; it is possible that some forms are relatively nontoxic, while others are highly toxic. This paper reviews what is known about the nature of nontransferrin-bound iron and describes the methods currently available to quantify this important serum component.