What is likely to occur first in iron deficiency anemia?

In the context of iron deficiency anemia, a decrease in serum ferritin is likely to occur first. Ferritin is a protein that stores iron and reflects the body's iron stores. When there is insufficient iron available, such as in iron deficiency anemia, the body's iron stores deplete, leading to decreased levels of ferritin in the serum.

This decrease in ferritin typically precedes changes in serum iron, total iron-binding capacity (TIBC), and transferrin. As the body continues to deplete its iron stores, serum iron levels may drop, and TIBC can increase due to the body's attempt to capture more iron from the diet. Additionally, transferrin levels may rise as it is a transport protein for iron. However, these changes occur after serum ferritin decreases, making it the earliest indicator of iron deficiency in the progression toward anemia.