Ferritin is a protein found inside cells that stores iron within the body. This protein holds iron in a safe, non-toxic form until the body requires it for various biological processes. Measuring the amount of ferritin in the blood, known as serum ferritin, provides a snapshot of the body’s total iron reserves. Abnormal ferritin levels, both low and high, signal a disruption in the balance of iron regulation necessary for overall health.
Ferritin’s Primary Biological Role
Ferritin is a large, globular protein complex that forms a hollow, spherical structure capable of accommodating up to 4,500 iron atoms. Its primary function is to sequester excess iron, storing it in a soluble and non-toxic ferric \(\text{(Fe}^{3+})\) state.
This sequestration is necessary because free iron is highly reactive and can catalyze the formation of harmful free radicals, leading to oxidative stress and cellular damage. By buffering the intracellular iron pool, ferritin ensures iron is available for essential functions, such as oxygen transport and DNA synthesis, while protecting cells from its toxic effects. Ferritin is found in virtually all cells, but the largest concentrations are in the liver, spleen, and bone marrow, which are the main sites for iron storage and recycling.
Interpreting the Serum Ferritin Test
The serum ferritin test is a standard blood analysis used to estimate the body’s total iron stores. Although ferritin primarily resides inside cells, a small amount is secreted into the bloodstream, and this circulating level reflects the overall amount of stored iron. A blood sample is taken and measured using a sensitive immunoassay.
In a healthy individual, the serum ferritin value is proportional to the size of the iron reserve. Interpreting the results requires considering various factors, as normal ranges differ based on age, sex, and the specific laboratory performing the test. Because inflammation can artificially raise ferritin levels, doctors often consider other iron markers, such as transferrin saturation, to obtain a complete picture of iron status.
Clinical Significance of Low Ferritin Levels
A low serum ferritin level is the most sensitive indicator of depleted iron stores, often preceding the development of anemia. This state signifies that the body lacks the reserves needed for normal cellular function. If the deficiency progresses, it can lead to iron-deficiency anemia, a condition where there is insufficient iron to produce enough healthy red blood cells for oxygen transport.
The most common causes of low ferritin include:
- Chronic blood loss, such as heavy menstrual bleeding or slow bleeding in the gastrointestinal tract.
- Inadequate dietary intake, particularly in vegetarians or vegans, as the body must absorb iron from food.
- Malabsorption issues, caused by diseases like celiac disease or Crohn’s disease, which prevent efficient iron absorption.
- Increased iron demand, such as during pregnancy or periods of rapid growth, if intake is not adjusted.
Symptoms associated with this deficiency arise from poor oxygen delivery and often include unexplained fatigue, weakness, dizziness, and pallor. Low ferritin can also cause poor concentration and difficulty breathing even before anemia develops.
Clinical Significance of High Ferritin Levels
Elevated serum ferritin, known as hyperferritinemia, can signify two different issues: true iron overload or a state of inflammation. Ferritin functions as an acute phase reactant, meaning its production increases in response to infection, injury, or chronic inflammation. In these cases, high ferritin is a protective mechanism where the body sequesters iron to withhold it from pathogens.
Conditions that commonly cause high ferritin due to inflammation include:
- Liver disease.
- Chronic kidney disease.
- Certain cancers.
- Metabolic syndrome, including obesity and fatty liver.
To determine if the high ferritin is due to inflammation, doctors often check other markers, such as C-reactive protein (CRP), and look for a normal transferrin saturation.
When high ferritin is not due to inflammation, it indicates genuine iron overload in the body’s tissues. The most common genetic cause is hereditary hemochromatosis, which causes the body to absorb excessive iron from the diet. Other causes of iron accumulation include excessive alcohol consumption, repeated blood transfusions, or taking too many iron supplements. Untreated iron overload can lead to serious organ damage in the liver, heart, and pancreas.
Management of Abnormal Ferritin Levels
The strategy for managing abnormal ferritin levels depends on identifying the underlying cause. For low ferritin indicating iron deficiency, the primary intervention is usually oral iron supplementation, often using ferrous sulfate. Treatment continues until iron stores are fully replenished. Dietary adjustments, such as increasing iron-rich foods, are also recommended, and addressing any source of chronic blood loss is necessary.
For patients with high ferritin, further testing is required to distinguish between iron overload and inflammation. If true iron overload is confirmed, the standard treatment is therapeutic phlebotomy, which involves regularly removing blood to deplete excess iron stores until the ferritin level falls within a healthy range. If high ferritin is due to an inflammatory condition, the focus shifts to treating the underlying disease, as the ferritin level will normalize once the inflammation is resolved. All interventions for abnormal ferritin levels must be conducted under medical supervision, as inappropriate treatment can be harmful.