Iron - the basics:
- Iron is supplied by the diet.
- As much as 70% of the iron in the body is found in the hemoglobin of the red blood cells (RBCs).
- The other 30% is stored in the form of ferritin and hemosiderin (=iron-storage complex within cells, not widely available).
- About 10% of the ingested iron is absorbed in the small intestine and transported to the plasma.
- Abnormal levels of iron are characteristic of many diseases, including iron-deficiency anemia and hemochromatosis (=Iron overload).
Where is iron found in the body?
Most iron in the body is bound to red blood cells or stored in the spleen and cannot be directly tested.
Iron is found in different parts of the body:
- In the blood. About 65% of all iron is in the blood. Iron in the blood is mostly bound to the transportation protein transferrin.
- In muscles
- In the liver (called ferritin)
- In enzymes in the body.
Iron and transferrin:
- After iron is absorbed in the small intestine and transported to the plasma, there the iron is bound to a globulin protein called transferrin and carried to the bone marrow for incorporation into hemoglobin.
- Transferrin exists in relation to the need for iron. When iron stores are low, transferrin levels increase, whereas transferrin is low when there is too much iron.
- Usually about one-third of the transferrin is being used to transport iron. Because of this, the blood serum has considerable extra iron-binding capacity, which is the Unsaturated Iron Binding Capacity (UIBC). The TIBC equals UIBC plus the serum iron measurement. Some laboratories measure UIBC, some measure TIBC, and some measure transferrin.
- The serum iron determination is a measurement of the quantity of iron bound to transferrin.
Why is iron so important?
- Iron is an essential element required for hemoglobin production.
- The human body requires iron to perform many vital physiological functions.
What is hemoglobin?
Hemoglobin oxygenates the blood. Without iron, red blood cells cannot reproduce in the body.
How is iron absorbed in the body?
- The body takes in iron from the food you eat so it is important to have good sources of iron in your diet. Only about 10% of the iron you consume is absorbed.
- The process of iron absorption is tightly regulated because your body does not have any biochemical ways of removing iron. Instead, iron is lost through processes such as bleeding, menstruation, and breast-feeding. Additionally, iron within the body is constantly being recycled and reused.
What does a serum test do?
A serum iron test measures iron levels in the serum component of the blood. A serum iron test is ordered after abnormal results are found in a hemoglobin test or a complete blood count, or when you are showing symptoms of anemia.
How is iron measured?
- Iron is often measured in micrograms per deciliter (mcg/dl), normal ranges for serum iron differ depending on an individual’s age and sex.
- Child-bearing women have the highest requirements for iron because of the monthly loss of blood in their menstrual cycles.
- If your results are abnormal, additional tests will determine whether iron is being stored in your liver, not being transported to the right places in your body, or what type of anemia you have.
Iron
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