ASCP | MLS | MLT | Hematology | Iron Kinetics and Laboratory Assessment

Summary

This ASCP preparation camp video explores the crucial role of iron in metabolic processes, its distribution in the body, and its transport mechanisms. The lecture covers iron's involvement in energy production, oxidation-reduction reactions, and the regulation of iron absorption through the liver's hepcidin response. It also delves into the laboratory assessment of body iron status, highlighting tests such as serum iron, total iron binding capacity, ferritin assays, and more advanced tests like soluble transferrin receptor and zinc protoporphyrin. These methods aid in diagnosing iron deficiencies and disorders, ensuring proper iron metabolism for healthy red blood cell production.

Takeaways

• 😀 Iron is essential for energy production in cells, playing a critical role in mitochondria and oxygen transport in red blood cells.
• 😀 The body does not excrete iron actively; instead, it recycles it to conserve as much as possible.
• 😀 Approximately 65% of body iron is contained in hemoglobin, 25% is stored in macrophages and hepatocytes, and 10% is in muscles, plasma, and enzymes.
• 😀 Iron is distributed into three compartments: functional (in hemoglobin, myoglobin, cytochromes), storage (in macrophages, hepatocytes), and transport (in the bloodstream via transferrin).
• 😀 Iron’s chemical ability to shift between ferrous (Fe2+) and ferric (Fe3+) states is crucial for its role in oxidation-reduction reactions.
• 😀 Systemic body iron regulation involves transport across the small intestine, where divalent metal transporter 1 and ferroportin play key roles.
• 😀 Hepcidin production in the liver regulates iron absorption by binding to ferroportin, reducing iron intake when stores are adequate.
• 😀 Transferrin, a protein that carries ferric iron in the blood, binds to iron and helps in its transport throughout the body.
• 😀 Cellular iron absorption is controlled via receptor-mediated endocytosis, where transferrin binds to transferrin receptor 1 on cell membranes.
• 😀 Laboratory tests such as serum iron, total iron binding capacity (TIBC), and ferritin levels are essential for assessing body iron status.
• 😀 The Prussian Blue stain is the gold standard for detecting tissue iron stores in bone marrow and liver biopsies, revealing ferric iron and hemosiderin.
• 😀 Elevated ferritin levels may indicate inflammation, so a low ferritin level is a more reliable indicator of iron deficiency.
• 😀 Soluble transferrin receptor (sTfR) levels increase when iron levels are low, making it a useful marker for iron deficiency anemia.
• 😀 Zinc protoporphyrin accumulation in red blood cells is a sign of iron deficiency and can be detected in fluorescence tests.

Q & A

What is the role of iron in the body?

Iron is critical for energy production in cells, particularly in the cytochromes of mitochondria. It also plays a key role in oxygen transport, being carried by hemoglobin in red blood cells.

What percentage of the body's iron is stored in hemoglobin?

About 65% of the body's iron is stored within hemoglobin in red blood cells of various stages.

What are the three compartments where iron is distributed in the body?

Iron is distributed into three compartments: the functional compartment (iron functioning in cells, e.g., hemoglobin), the storage compartment (iron stored in macrophages and hepatocytes), and the transport compartment (iron in transit in the plasma).

How does iron change its valence state in the body?

Iron changes its valence state from ferrous (Fe2+) to ferric (Fe3+) to participate in oxidation and reduction reactions, such as electron transport within mitochondrial cytochromes.

What role does hepcidin play in iron regulation?

Hepcidin is a protein produced by the liver that regulates iron absorption. When iron stores are sufficient, hepcidin binds to ferroportin, inactivating it and reducing iron absorption. When iron stores are low, hepcidin production decreases, allowing ferroportin to transport iron into the bloodstream.

What is the process by which iron is absorbed in the small intestine?

Iron is absorbed in the small intestine by the divalent metal transporter (DMT1), which transports ferrous iron (Fe2+) into enterocytes. The iron is then transported across the basal membrane into the bloodstream via ferroportin.

What is the significance of transferrin in iron transport?

Transferrin is a protein that binds to ferric iron (Fe3+) and transports it through the plasma. Once bound, the complex is known as transferrin and delivers iron to cells via transferrin receptors.

How does receptor-mediated endocytosis regulate cellular iron absorption?

Transferrin binds to transferrin receptor 1 on the cell membrane, which triggers endocytosis. Inside the cell, iron is released from transferrin into the cytoplasm, while transferrin is recycled back to the plasma.

What is ferritin and how is it related to iron storage?

Ferritin is a protein that stores iron within cells in a safe, non-toxic form. It can bind up to 4,000 iron ions. Ferritin levels in the blood correlate well with the amount of stored iron in the body.

What tests are commonly used to assess body iron status?

Common tests for assessing iron status include serum iron, total iron binding capacity (TIBC), percent transferrin saturation, Prussian Blue staining, ferritin assays, soluble transferrin receptor levels, reticulocyte hemoglobin content, and zinc protoporphyrin levels.