Iron, an essential mineral, plays a fundamental role in the human body, primarily by facilitating oxygen transport and supporting energy production. It is a key component of hemoglobin, the protein within red blood cells responsible for carrying oxygen from the lungs to tissues. Iron also contributes to metabolic processes, enabling the body to generate energy. Iron deficiency, a condition where the body lacks sufficient iron, is a common nutritional deficiency affecting a significant portion of the global population.
Early Iron Depletion
The initial stage of iron deficiency is early iron depletion. At this point, the body’s iron reserves begin to diminish, but red blood cell production remains unaffected. Iron is stored primarily as ferritin, found within cells and circulating in the blood. Consequently, the diagnostic marker for this stage is a low serum ferritin level, typically below 30 ng/mL.
During early iron depletion, individuals are usually asymptomatic. The body can still meet its iron demands for essential functions by drawing from its remaining reserves. Hemoglobin levels and red blood cell characteristics remain within normal ranges, as enough iron is available for red blood cell production. The primary indicator of this stage is the declining iron stores.
Latent Iron Deficiency
The second stage, latent iron deficiency, signifies a more pronounced depletion of iron stores. At this stage, iron reserves are severely diminished, and the supply of iron to the bone marrow becomes insufficient to support normal red blood cell production. This deficiency impairs the synthesis of heme, a component of hemoglobin, leading to subtle changes in developing red blood cells.
Diagnostic markers include decreased transferrin saturation (TSAT) and an increase in total iron-binding capacity (TIBC). Transferrin saturation reflects the amount of iron bound to transferrin, the protein that transports iron in the blood, and typically falls below 16%. TIBC, which indicates the blood’s capacity to bind iron, often rises as the body attempts to absorb more iron. While overt anemia is not yet present, some individuals may begin to experience mild symptoms such as fatigue or reduced exercise tolerance. These symptoms arise due to the body’s impaired ability to transport oxygen efficiently.
Iron Deficiency Anemia
The third stage is iron deficiency anemia (IDA), where iron deficiency significantly impairs hemoglobin synthesis. This leads to a reduction in healthy red blood cells and a decrease in overall hemoglobin levels. The red blood cells produced are smaller than normal (microcytic) and paler in color (hypochromic) due to insufficient hemoglobin content.
The symptoms of IDA are more pronounced, reflecting the body’s struggle to deliver adequate oxygen to tissues. Common symptoms include severe fatigue, generalized weakness, and pale skin. Individuals may also experience shortness of breath, a rapid heartbeat, and dizziness with activity. More specific signs can develop, such as brittle nails, a sore or smooth tongue (glossitis), and unusual cravings for non-nutritive substances like ice or dirt, a condition known as pica.
Key diagnostic markers for IDA include low hemoglobin and hematocrit levels, which indicate a reduced red blood cell mass. Hemoglobin levels typically fall below 130 g/L for men and 120 g/L for non-pregnant women. Mean corpuscular volume (MCV) and mean corpuscular hemoglobin (MCH) are low, indicating the small size and reduced hemoglobin content of red blood cells. Low serum ferritin and transferrin saturation, along with an elevated total iron-binding capacity, further confirm the iron-deficient state.