- Iron is essential for hemoglobin and myoglobin and the total body iron content is around 3-5g, with most found in blood, liver, bone marrow and muscles. - Daily iron requirements vary from 20mg for adults to 40mg for pregnant women. Absorption is regulated to maintain iron balance in the body. - Sources of iron include leafy vegetables, pulses, cereals, liver and meat. Absorption is affected by factors like ascorbic acid and interfering substances like phytic acid.

1. Sanjay George
IRON METABOLISM

2. DISTRIBUTION OF IRON
• Total body iron content is 3 to 5 gm, 75% of which is
present in blood. The rest is in liver, bone marrow and
muscles.
• 75% of the blood iron is hemoglobin, 5% myoglobin and
15% ferritin.

3. REQUIREMENT OF IRON
• Daily requirement for an adult Indian is 20mg of iron out
of which 1-2mg is absorbed.
• Children between 13-15 years need 20-30 mg/day.
• Pregnant women need 40 mg/day. Transfer of iron and
calcium from mother to fetus occurs mainly during last
trimester of pregnancy.

4. • During first three months of life, iron intake is negligible
and during this time child is dependent on iron reserve.
• Premature babies are at risk of iron deficiency anemia.
• After 3 months of life, diet supplementation with cereals
essential for supplying iron requirement.

5. SOURCES OF IRON
• Leafy vegetables
• Pulses
• Cereals
• Liver
• Meat
• Jaggery

6. FACTORS AFFECTING ABSORPTION OF IRON
• Reduced form of iron
• Ascorbic acid – Helps to reduce ferric ions
• Interfering substances – Phytic acid(in cereals) and
Oxalic acid(in leafy vegetables) forms insoluble salts.
• Other minerals like calcium, copper, lead and
phosphates will inhibit iron absorption.

7. MUCOSAL BLOCK THEORY
• Duodenum and jejunum are sites of absorption.
• Iron metabolism is maintained by regulation at level of
absorption and not by excretion. – One Way Element
• When iron stores in body are depleted absorption is
enhanced. Reverse when adequate quantity is present.

8. ABSORPTION
Fe 2+
Divalent metal
transporter
Fe 2+ Fe 3+ Ferritin
Fe 2+ crosses
membrane
Fe 3+ transferrin in
blood stream

9. REGULATION OF ABSORPTION
• Mucosal Regulation
• Stores Regulation
• Erythropoietic regulation – erythroid cells signal
mucosa to increase absorption

10. IRON TRANSPORT
• Transport form of iron is transferrin, a beta glubulin.
Normal plasma level – 250mg/100ml. Increased in iron
deficiency.
• Total Iron Binding Capacity in plasma is 400mg/100ml,
this is provided by transferrin.
• One third of this capacity is saturated with iron, this
protein bound iron(serum iron) is about 120mg/dL.
• Ceruloplasmin is the ferroxidase which oxidises ferrous
to ferric state.

11. • Transferrin receptors are present on most body cells,
especially on cells which synthesize heme.
• Iron transferrin complex taken up by body cells by
receptor mechanism. The receptor binds 2 molecules of
transferrin and is internalized. Iron is taken up by the
cells and the receptor molecules are externalized.
• Reticulocyte can internalize 1 million atoms of iron per
minute.

12. STORAGE OF IRON
• The storage form of iron is ferritin.
• Its seen in intestinal mucosal cells, liver, spleen and
bone marrow.
• Apoferritin can take up to 4000 atoms of iron per
molecule.

13. IRON IS CONSERVED
• When RBC is lysed Hb is released into circulation.
Being low molecular weight, Hb will be lost through
urine.
• To prevent this Hb is immediately taken up by
haptoglobin an alpha globulin
• Haptoglobin is an acute phase protein and its level is
increased in inflammation
• Globin part is removed from Hb, and the heme is
released into circulation.

14. • In order to prevent excretion of haeme through urine,
heme is bound with hemopexin.
• Hemopexin is a beta globulin whose levels are
enhanced during increased haemolysis.
• Heme-hemopexin complex is taken up by hepatocytes.
• The porphyrin is removed and the free iron is either
stored or utilized.

15. EXCRETION
• Iron is a one way element. Regulation of homeostasis
is done at level of absorption.
• Almost no iron is excreted through urine. Feces
contains unabsorbed iron as well iron trapped in
intestinal cells that are desquamated.
• 30% of intestinal lining cells are replaced every day
hence this loss is considerable.
• All cells in skin contain iron. Hence iron is lost by
shedding of upper layers of skin.

16. HEMOGLOBIN
• It’s the chief respiratory pigment in humans. Each Hb
molecule consists of 4 heme residues located in globin
chains.
• Iron present in Fe 2+ state
• Normal Values:
• Male : 13 – 18 g/dL
• Female : 11.5 – 16.5 g/dL