Mechanisms of iron loading and toxicity.

Normal iron homeostasis is a finely balanced system that reflects iron absorption, loss and utilization. The body has no mechanism for the active excretion of iron, so body iron levels are controlled at the point of absorption in the small intestine. Disturbances in this equilibrium, such as those leading to enhanced absorption, can have significant clinical consequences. Continued excessive iron uptake is followed by iron deposition in various tissues, ultimately leading to tissue damage, and possibly end-organ failure. In this review, current concepts in normal iron homeostasis, and iron loading are explained. The clinical consequences as well as the differences between primary and secondary iron loading are also reviewed, and some future research priorities are discussed.