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How does iron metabolism occur in the body, and why is ferritin not always a marker of iron deficiency?
Iron is essential for every cell in our body. In addition to its role in erythrocyte production and oxygen transport, iron plays a crucial role in mitochondrial function and energy production, and is a necessary component in the construction and functioning of many enzymes.
However, free iron can be highly toxic, so it must be bound to proteins to be safely transported and stored in the body.
Imagine that iron atoms are important individuals residing in an expensive hotel in Venice, moving exclusively through canals (in our case, through blood vessels) accompanied by the gondolier Transferrin. Upon departure, they are always greeted by the guardian porter Hepcidin, who assesses the situation and opens or closes the doors for our Iron.
Hepcidin is a hormone produced in the liver that regulates the body’s iron needs and determines how much can enter the bloodstream. It also controls iron absorption from food. If there is a deficiency, it increases absorption; if there is excess or inflammation, it decreases absorption.
Next, iron binds to the transport protein transferrin. This gondola has a limited number of seats for its passengers—iron atoms.
Magnesium, amino acids, and insulin are also important participants in the process. They are building blocks for the transferrin gondola. If they are insufficient, we cannot build enough boats to transport iron.
In addition to the porter Hepcidin and the gondolier Transferrin, several other responsible individuals are involved in the transportation of Iron: Vitamin A, Magnesium, and Copper, which help load Iron into transferrin gondolas, and the senior Ceruloplasmin—a protein-antioxidant that manages this process.
If these compounds are unavailable, iron will not be “loaded into the gondolas” and will not reach the cells, even if it is sufficient in the body. This leads to decreased production of new erythrocytes, hemoglobin, and transferrin saturation with iron (this indicator in a blood test reflects the “filling of the iron gondolas”).
Thus, signs of anemia are not always true iron deficiency but may be due to its regulation disorder, associated with deficiencies of magnesium, copper, amino acids, vitamin A, C, etc.
Can serum ferritin levels be a reliable marker of iron status in the body?
Ferritin is a storage protein that serves as an iron depot and is also a marker of acute inflammation, autoimmune diseases, and a cancer marker, which can complicate the assessment of iron balance.
Viruses, bacteria, and cancer cells, like us, require iron for their life and proliferation.
When inflammation begins in the body, Hepcidin activity increases (remember, this is the same porter who controls the exit). It locks the doors to invaders, reducing access to iron in the bloodstream. Now, it will be securely stored in the “Ferritin” hotel, the level of which rises during inflammation.
The load on the gondolier Transferrin also decreases; the boats sail through the canals-vessels unfilled, and the transferrin iron saturation level drops.
Ferritin can contain up to 4,500 iron atoms, but if the hotel is overcrowded, some free iron manages to enter the bloodstream and reach the cells, leading to oxidative damage of cellular DNA, membranes, mitochondria, lipids, and can also be used by invaders to develop their colonies.
The problem with ferritin is that the optimal level in the blood and the level indicating inflammation are controversial. If ferritin levels below 10 ng/L are considered critically low and indicate existing iron deficiency, a high level does not always exclude iron deficiency. A comprehensive assessment of the entire iron pathway in the body is needed, excluding anemia of chronic diseases, and determining the causes of iron deficiency. Sometimes, this is quite a challenging task.
Improving iron balance requires attention to all nutrients in the diet, and the prescription of iron supplements should be done only by a doctor.
Key Points:
- Iron is an essential component for our body’s functioning, but free iron can be highly toxic, so it must be bound to proteins to be safely transported and stored in the body.
- Hepcidin is a hormone that controls iron absorption from food.
- Transferrin is a transport protein that safely delivers iron to cells and organs.
- Vitamin A, magnesium, copper, amino acids, and insulin are important participants in the iron transportation process. If these compounds are unavailable, iron will not reach the cells, even if it is sufficient in the body.
- Viruses, bacteria, and cancer cells, like us, require iron for their life and proliferation. When inflammation begins in the body, protective mechanisms are activated that limit access to iron. It is important not to confuse anemia of inflammation with iron deficiency and mistakenly start taking iron supplements.
- Ferritin is a storage protein that serves as an iron depot and is also a marker of acute inflammation, autoimmune, and oncological diseases. In iron deficiency, its level in the blood serum significantly decreases; during inflammation, it increases.
- Free iron, which ferritin and transport proteins cannot bind, can lead to oxidative damage of cellular and organ structures.
