Which statement correctly describes the relationship between transferrin saturation and iron deficiency?

Which statement correctly describes the relationship between transferrin saturation and iron deficiency?

• A. Transferrin saturation is increased
• B. Transferrin saturation is decreased
• C. Transferrin saturation is unchanged
• D. Transferrin saturation is not related to iron status

Answer: (B)

Transferrin saturation shows what fraction of transferrin’s iron-binding sites are actually occupied by iron. It is calculated as serum iron divided by total iron-binding capacity (TIBC) times 100. In iron deficiency, serum iron falls while the liver increases transferrin production, raising TIBC. With a lower serum iron and a higher TIBC, the ratio—and thus the saturation—decreases. So, transferrin saturation is decreased in iron deficiency. The other possibilities don’t fit because they would require more iron to be bound, no change, or no relation to iron status, which contradicts the way iron delivery is reduced in deficiency.

Transferrin saturation shows what fraction of transferrin’s iron-binding sites are actually occupied by iron. It is calculated as serum iron divided by total iron-binding capacity (TIBC) times 100. In iron deficiency, serum iron falls while the liver increases transferrin production, raising TIBC. With a lower serum iron and a higher TIBC, the ratio—and thus the saturation—decreases. So, transferrin saturation is decreased in iron deficiency. The other possibilities don’t fit because they would require more iron to be bound, no change, or no relation to iron status, which contradicts the way iron delivery is reduced in deficiency.