Ferritin

Ferritin is an iron-protein complex found in most tissues, but particularly the bone marrow and reticuloendothelial system.

Clinically, its importance is:

• as an acute phase protein
• as a non-specific index of liver disease
• its close relationship to body stores of iron. Thus a low serum ferritin implies iron deficiency. Conversely, high ferritin can imply iron overload states. However, given the first two points in the list, ferritin levels must be interpreted in the light of ongoing inflammation and liver disease.

Notes (1):

• whilst low serum ferritin (SF) is a sensitive and specific indicator of low total body iron stores, elevated SF is sensitive but very nonspecific for iron overload
  • a normal SF rules out iron overload
• raised SF
  • only 10% of cases of elevated SF are due to iron overload - chronic alcohol consumption, metabolic syndrome, obesity, diabetes, malignancy, infection and inflammatory conditions explain 90% of causes of elevated SF
    • there is a well-established link between elevated SF, metabolic syndrome and fatty liver
    • liver disease is a cause of elevated SF
      • damaged hepatocytes leak ferritin into the serum
        • in liver disease, SF can be considered as another type of liver function test (LFT)
  • elevations of SF in the range 300-1000 µg/L are common, and often reflect the presence of the previously listed conditions
    • mild elevations below 1000 µg/L are 'tolerable' and in the absence of hereditary haemochromatosis, the risk of hepatic iron overload is exceedingly low
    • conditions such as malignancy, infection and inflammatory conditions may all cause elevated SF
      • normal screening tests for C-reative protein (CRP), erythrocyte sedimenation rate (ESR) and antinuclear antibody (ANA) can help exclude the presence of these conditions
    • specialist review is mandatory if SF exceeds 1000 µg/L due to the increased risk of fibrosis and cirrhosis above this threshold

Reference:

• Goot K et al. Elevated serum ferritin - what should GPs know?Aust Fam Physician. 2012 Dec;41(12):945-9.