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PA14.1-2 | Welcome to Iron Metabolism: Absorption, Transport, Storage, Regulation
Learning Objectives
- Describe the distribution of total body iron across the three pools — functional (haemoglobin, myoglobin, enzymes), storage (ferritin, hemosiderin), and transport (transferrin) — and explain why these pools differ in clinical detectability
- Trace the pathway of dietary iron from duodenal lumen to erythroblast: DMT1 → enterocyte → ferroportin → plasma → transferrin → TfR-mediated endocytosis
- Explain transferrin saturation and TIBC as derived measures and interpret them in a given iron-study panel
- Distinguish ferritin from hemosiderin as storage forms and explain why serum ferritin is the best single marker of iron stores — and when it becomes unreliable
- Describe hepcidin's role as the master regulator of systemic iron homeostasis and predict the direction of hepcidin change in iron deficiency versus chronic inflammation
- Sequence the three stages of progressive iron depletion and identify which laboratory parameter falls first in each stage
INSTRUCTIONS
You already classified anaemia by MCV in the previous cluster. You know microcytic anaemia exists. Now the question is: why does iron deficiency produce that pattern? The answer lives in iron metabolism — a beautifully regulated system that you studied in Year-1 Biochemistry, but in fragments. This module re-assembles those fragments into one coherent picture. By the time you finish, when you see 'low Hb, low MCV, low ferritin' on a CBC report, you will know exactly which pool is depleted, why it depleted, and what the body tried to do about it. That understanding is the foundation for every microcytic anaemia you will diagnose for the rest of your career.
References
- Robbins and Cotran Pathologic Basis of Disease, 10th ed., Chapter 14 — Red Blood Cell Disorders (textbook)
- Hoffbrand's Essential Haematology, 8th ed., Chapter 2 — Iron Metabolism and Clinical Aspects of Iron Deficiency (textbook)
- WHO/IAEA Serum Ferritin Concentrations for the Assessment of Iron Status and Iron Deficiency in Populations (2020) (guideline)
- Muckenthaler MU et al. A Red Carpet for Iron Metabolism. Cell. 2017;168(3):344-361. (review)
Version 2.0 | NMC CBUC 2024