Because HH is an iron overload disease, reviewing the basic principles of iron metabolism helps understand 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 standard functions. However, excessive quantities may be toxic.
Two main types of iron-containing compounds are usually 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 (i.e., 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.
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