Iron

Ferritin is the iron store and the most sensitive marker in iron deficiency – it falls long before haemoglobin or MCV become noticeable. Many people have symptoms such as hair loss, exhaustion and restless legs while the blood count and haemoglobin are still normal. The reference range is set out in your findings report.

How iron acts in the body

About two thirds of the body's iron is in the haemoglobin of red blood cells, which carries oxygen from the lungs to the tissues; another part is in the myoglobin of the muscles and in the mitochondrial enzymes that produce energy. Iron is absorbed in the duodenum, transported in the blood by transferrin and stored as ferritin. The body can hardly excrete iron actively – only absorption is regulated, via the liver hormone hepcidin. During inflammation hepcidin rises, absorption falls and ferritin rises as part of the inflammatory response.

Low iron – what happens in the body?

First the stores empty (ferritin falls), then iron is lacking for blood formation: red blood cells become smaller and contain less haemoglobin, and the blood carries less oxygen. This shows as exhaustion, shortness of breath on exertion, palpitations and pallor. Iron-dependent enzymes in hair roots, skin, nails and brain work less well – hair loss, brittle nails, cracked corners of the mouth, difficulty concentrating and restless legs may follow. Causes are blood loss (for example through menstruation), low intake, increased need (pregnancy, growth, sport) or impaired absorption.

High iron – what happens in the body?

Because iron is hardly excreted, excess iron is deposited in the liver, heart, pancreas and joints; free iron produces reactive oxygen compounds there and thus oxidative stress. The most common inherited cause is haemochromatosis. Raised storage values also occur with inflammation, liver disease and metabolic disorders without there being too much iron in the body – which is why ferritin, transferrin saturation and inflammation markers are considered together.