Because HH is a disease of iron overload, a review of the basic principles of iron metabolism is helpful in understanding its pathophysiology. A more comprehensive discussion of iron metabolism is found in the reference list. (2)
Iron is needed by all body cells and is crucial for oxygen transport, oxidative metabolism, and cell growth and proliferation. To serve these functions, iron must be bound to protein. Iron is potentially harmful when ionized or complexed to inorganic compounds. Iron must be present in amounts sufficient to carry out these normal functions. However, excessive amounts may be toxic.
Two main types of iron-containing compounds are normally found in the body:
- Compounds involved in metabolic or enzymatic functions
- Compounds involved with transport or storage
Hemoglobin, myoglobin, cytochromes and other proteins are involved with oxygen transport and utilization. Iron in hemoglobin comprises about 67% of total body iron (ie, 2.5 g of the total 3-4 g of iron); thus erythrocytes are rich in iron. Approximately 27% of iron is found in storage compounds. Myoglobin, other tissue iron, and transport iron comprise the remaining 6% of total body iron. (2)