What is the Difference Between Ferritin and Hemosiderin

The key difference between ferritin and hemosiderin is that ferritin is an intracellular protein that stores iron and releases it in a controlled manner, while hemosiderin is an iron storage complex that is composed of partially digested ferritin and lysosomes.

Iron is stored in the human liver in two forms: ferritin and hemosiderin. Ferritin is a protein with a capacity of storing about 4500 iron (III) ions per protein molecule. If this capacity exceeds, a complex of iron forms with phosphate and hydroxide, and it is known as hemosiderin.

1. Overview and Key Difference
2. What is Ferritin
3. What is Hemosiderin
4. Similarities – Ferritin and Hemosiderin
5. Ferritin vs Hemosiderin in Tabular Form
6. Summary – Ferritin vs Hemosiderin

What is Ferritin?

Ferritin is an intracellular protein that stores iron and releases it in a controlled manner. It is a universal intracellular protein. This protein is produced by almost all living organisms, including archaea, bacteria, algae, higher plants, and animals. Therefore, it is the primary intracellular iron storage protein functioning in both prokaryotes and eukaryotes. It normally keeps iron in a soluble and non-toxic form in humans. It also acts as a buffer against iron deficiency and iron overload.

Figure 01: Ferritin

Usually, ferritin is found as a cytosolic protein in tissues. However, small amounts of ferritin can be secreted into the serum as well. Serum ferritin functions as an iron carrier. Moreover, plasma ferritin is an indirect marker of the total amount of iron stored in the human body. Therefore, plasma ferritin is used as an indirect marker for iron deficiency anemia. This type of test is called a ferritin test. Furthermore, ferritin is a globular protein. It is a complex protein that consists of 24 protein subunits. Multiple metal-protein interactions can be found in the structure. The ferritin molecule that is not combined with iron is known as apoferritin.

What is Hemosiderin?

Hemosiderin is an iron storage complex composed of partially digested ferritin and lysosomes. The breakdown of heme of haemoglobin gives rise to biliverdin and iron. Later, the body traps and stores this released iron in the form of hemosiderin in tissues. Moreover, hemosiderin also forms due to the abnormal pathway of ferritin. Hemosiderin is only found within the cells. It appears as a complex of ferritin, denatured ferritin, and other materials in these cells. Normally, the iron deposits within hemosiderin are poorly available to supply iron when needed.

Ferritin and Hemosiderin - Side by Side Comparison

Figure 02: Hemosiderin

Excessive accumulation of hemosiderin is usually detected within cells of the mononuclear phagocyte system (MPS) or occasionally in epithelial cells of the liver and kidney. Furthermore, hemosiderin is commonly found in macrophages and is abundant in situations following hemorrhage. Therefore, excessive accumulation of hemosiderin can be observed in various diseases such as sickle cell anemia and thalassemia.

What are the Similarities Between Ferritin and Hemosiderin?

Ferritin and hemosiderin are two forms of iron stored mostly in the human liver.
Both forms can be observed within the cells.
In fact, they are predominantly found in liver cells.
Hemosiderin can be formed due to the abnormal pathway of ferritin.
They play a pivotal role in iron homeostasis in the body.

What is the Difference Between Ferritin and Hemosiderin?

Ferritin is an intracellular protein that stores iron and releases it in a controlled manner, while hemosiderin is an iron storage complex that is composed of partially digested ferritin and lysosomes. Thus, this is the key difference between ferritin and hemosiderin. Furthermore, ferritin is found both in cells as well as in plasma, while hemosiderin is only found within cells.

The below infographic presents the differences between ferritin and hemosiderin in tabular form for side-by-side comparison.

Summary – Ferritin vs Hemosiderin

Ferritin and hemosiderin are two correlated molecules, which are two forms of irons stored mostly in the human liver. Both forms can be observed within the cells. Ferritin is an intracellular protein that stores iron and releases it in a controlled manner, while hemosiderin is an iron storage complex that is composed of partially digested ferritin and lysosomes. Iron stored in ferritin is readily available when the body needs it. In contrast, iron stored in hemosiderin is poorly available when the body needs it. So, this summarizes the difference between ferritin and hemosiderin.

Reference:

1. “Ferritin.” An Overview | ScienceDirect Topics.
2. Saito, Hiroshi. “Metabolism of Iron Stores.” Nagoya Journal of Medical Science, Nagoya University.