AIIMS CRE, SNO-2024: In the human body, the largest amount of iron is present in:

AIIMS CRE, SNO-2024

Biochemistry & Nutrition

Easy

Appeared in: AIIMS CRE, SNO-2024

Explanation

The largest portion of iron in the human body is found in haemoglobin.
Haemoglobin, located in red blood cells, contains approximately 65-70% of the total body iron.
Its primary function is to bind and transport oxygen from the lungs to the rest of the body's tissues.
The total amount of iron in haemoglobin in an adult male is around 2500 mg.

Option A: Ferritin is the primary storage form of iron, not the compartment with the largest amount. It holds about 25-30% of the body's iron in reserve.
Option B: Myoglobin contains a small fraction of the body's iron (about 4-5%) and is localized to muscle tissue for oxygen storage.
Option D: Transferrin is the protein that transports iron in the blood plasma, but it carries a very small amount (less than 0.1%) of the total body iron at any given time.

Visual 1: Pie Chart - A pie chart illustrating the percentage distribution of iron in the body (Haemoglobin, Ferritin/Hemosiderin, Myoglobin, and other proteins). This provides a quick visual comparison.
Visual 2: Diagram - A diagram of iron metabolism, showing the cycle of absorption from the gut, transport by transferrin, incorporation into haemoglobin in the bone marrow, and recycling by macrophages after red blood cell breakdown. This helps visualize the dynamic nature of iron in the body.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Distribution of iron in the human body as background academic context rather than a clinical decision trigger.
Understanding iron distribution is crucial for diagnosing and managing anaemia. Serum ferritin is the most sensitive early indicator of iron deficiency because storage iron is depleted before haemoglobin levels fall.
A nurse monitoring a patient for anaemia would look at both haemoglobin (to assess oxygen-carrying capacity) and ferritin (to assess iron stores). Low ferritin with normal haemoglobin indicates early, pre-anemic iron deficiency.
What if? If a patient has chronic kidney disease, they often have decreased production of erythropoietin, leading to lower red blood cell production. This reduces the amount of iron incorporated into haemoglobin, even if iron stores (ferritin) are adequate. The primary problem is not iron availability but red cell synthesis.

How to Approach the Question

This is a factual recall question. First, identify the core concept being tested, which is the distribution of iron in the human body.
Recall the different proteins involved in iron function and storage: Haemoglobin, Myoglobin, Ferritin, and Transferrin.
Compare the relative amounts of iron associated with each protein. Remember that the primary function of iron is oxygen transport, which points to haemoglobin as the major component.
Eliminate the other options based on their roles: Ferritin is for storage, Myoglobin is for muscle oxygen storage, and Transferrin is for transport, all of which involve smaller quantities of iron than the total amount in circulation within red blood cells.

Concept Tested & Keywords

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KD Tripathi - Essentials of Medical Pharmacology (6th Edition) p. 455-457