I am an mbbs student from Lakhimpur Medical college, Assam ..It was my presentation on Iron Metabolism

1. IRON METABOLISM
PRESENTED BY – BIKASH PATGIRI,
1ST YEAR MBBS , LAKHIMPUR
MEDICAL COLLEGE, ASSAM

2. Contents
1. Distribution of iron in our body
2. Biochemical function
3. Sources of iron
4. Absorption, transport and storage of iron
5. Factors affecting absorption of iron
6. Excretion of iron
7. Iron metabolism
8. Disease states

3. Distribution of iron in our body
 The total content of iron in an adult body is 3-5 g.
 About 70% of this occurs in the erythrocytes of blood as a constituent of hemoglobin.
 At least 5% of body iron is present in myoglobin of muscle.
 Heme is the most predominant iron-containing substance. It is a constituent of several
proteins/enzymes
 (hemoproteins)—hemoglobin, myoglobin, cytochromes, xanthine oxidase, catalase, tryptophan
pyrrolase, peroxidase.
 Certain other proteins contain non-heme iron e.g. transferrin, ferritin, hemosiderin.

5. Biochemical functions of iron
 1. Iron mainly exerts its functions through the compounds in which it
is present. Hemoglobin and myoglobin are required for the transport
of O 2 and CO 2.
 2. Cytochromes and certain non-heme proteins are necessary for
electron transport chain and oxidative phosphorylation.
 3. Peroxidase, the lysosomal enzyme, is required for phagocytosis and
killing of bacteria by neutrophils.
 4. Iron is associated with effective immuno-competence of the body.

6. Sources of iron
 Rich sources — Organ meats (liver, heart,
kidney).
 Good sources — Leafy vegetables, pulses,
cereals, fish, apples, dried fruits, molasses.
 Poor sources — Milk, wheat, polished rice.

7.  Iron is mainly absorbed in the stomach and duodenum.
 In normal people, about 10% of dietary iron is usually absorbed. However, in iron deficient
(anemic) individuals and growing children, a much higher proportion of dietary iron is
absorbed to meet the increased body demands.
 Iron is mostly found in the foods in ferric form (Fe3+ ), bound to proteins or organic acids. In
the acid medium provided by gastric HCl, the Fe3+ is released from foods. Reducing
substances such as ascorbic acid (vitamin C) and cysteine convert ferric iron (Fe3+ ) to ferrous
form (Fe2+ ).
 Iron in the ferrous form is soluble and readily absorbed.
Absorption, transport and storage of iron

9.  1. Acidity, ascorbic acid, alcohol, fructose and cysteine promote iron absorption.
 2. In iron deficiency anemia, Fe absorption is increased to 2-10 times that of normal.
 3. Small peptides and amino acids favour iron uptake.
 4. Phytate (found in cereals) and oxalate (found in leafy vegetables) interfere with Fe
absorption.
 5. A diet with high phosphate content decreases Fe absorption while low phosphate
promotes.
 6. Impaired absorption of iron is observed in mal-absorption syndromes such as steatorrhea.
 7. In patients with partial or total surgical removal of stomach and/or intestine, iron
absorption is severely impaired.
Factors affecting absorption of iron

10. Iron in the mucosal cells : The iron (Fe 2+ )
entering the mucosal cells by absorption is
oxidized to ferric form (Fe3+ ) by the enzyme
ferroxidase. Fe 3+ then combines with apoferritin
to form ferritin which is the temporary storage
form of iron. From the mucosal cells, iron may
enter the blood stream (which mainly depends
on the body needs) or lost when the cells are
desquamated.

11. Transport of Fe in the plasma : The iron liberated from the ferritin of
mucosal cells enters the plasma in ferrous state. Here, it is oxidized to
ferric form by a copper-containing protein, ceruloplasmin which
possesses ferroxidase activity. Another cuproprotein ferroxidase II also
helps for the conversion of Fe2+ to Fe 3+.Ferric iron then binds with a
specific iron-binding protein, namely transferrin or siderophilin (a
glycoprotein with mol. wt.90,000). Each transferrin molecule can bind
with two atoms of ferric iron (Fe 3+ ). The plasma transferrin
(concentration 250 mg/dl) can bind with 400 mg of iron/dl plasma. This
is known as total iron binding capacity (TIBC) of plasma.

12. Storage of iron : Iron is stored in liver, spleen
and bone marrow in the form of
ferritin. In the mucosal cells, ferritin is the temporary
storage form of iron. A molecule of apoferritin (mol.
wt. 500,000) can combine with 4,000 atoms of iron.
The maximum iron content of ferritin on weight basis
is around 25%.
Hemosiderin is another iron storage protein
which can hold about 35% of iron by weight.
Hemosiderin accumulates in the body (spleen,
liver) when the supply of iron is in excess of
body demands.

13. Excretion of iron
 Iron is a one-way element. That is, very little of it is excreted.
 Any type of bleeding will cause loss of iron from the body. Menstrual flow is the
major cause for loss of iron in women. Women up to menopause will lose iron at a
rate about 1mg/day. The loss in male is less than 0.5ms/day.
 Almost no iron is excreted through urine. Feces contain unabsorbed iron as well as
iron trapped in the intestinal cells, which are then desquamated. About 30% of cells
in the intestinal lining is replenished everyday, and so this loss is considerable.
 All the cells in skin contain iron. The upper layer of skin cells are constantly being
lost, and this is another route for iron loss from the body.

14. Iron is a one way substance
Iron metabolism is unique as it operates in a closed system. It is very efficiently utilized and
reutilized by the body. Further, iron losses from the body are minimal (< 1 mg/day) which may
occur through bile, sweat, hair loss etc. Iron is not excreted into urine. Thus, iron differs from the
vitamins or other organic and inorganic substances which are either inactivated or excreted during
the course of metabolic function. Hence, iron is appropriately regarded as a one-way substance.
Iron entry into the body is controlled at the absorption level, depending on the body needs.
Thus the periodical blood loss in menstruating women increases its requirements. Increased iron
demands are also observed in pregnancy, lactation, and in growing children.

15. Iron metabolism
A general overview of iron
metabolism is depicted in Fig.
It shows the distribution of
iron in the body and its
efficient reutilization. It may be
noted that 1-2 mg of iron is
absorbed per day to replace
the loss.

16. Disease states
a. This is the most prevalent nutritional disorder worldover, including the well developed countries (e.g. USA).
b. Several factors may contribute to iron deficiency anemia.
c. These include inadequate intake or defective absorption of iron, chronic blood loss, repeated pregnancies and hookworm
infections.
d. Strict vegetarians are more prone for iron deficieny anemia. This is due to the presence of inhibitors of iron absorption in
the vegetarian foods, besides the relatively low content of iron.
e. Iron deficiency anemia mostly occurs in growing children, adolescent girls, pregnant and lactating women.
f. It is characterized by microcytic hypochromic anemia with reduced blood hemoglobin levels (<12 g/dl). The other
manifestations include apathy (dull and inactive), sluggish metabolic activities, retarded growth and loss of appetite.
Treatment : Iron deficiency is treated by supplementation of iron along with folic acid and vitamin C.
1. Iron deficiency anemia

17. 2. Hemosiderosis
a. This is a less common disorder and is due to excessive iron in the body.
b. It is commonly observed in subjects receiving repeated blood transfusions over the years, e.g. patients of
hemolytic anemia, hemophilia.
c. As already stated, iron is a one-way compound, once it enters the body, it cannot escape.
d. Excessive iron is deposited as ferritin and hemosiderin.
e. Hemosiderosis is commonly observed among the Bantu tribe in South Africa. This is attributed to a high
intake of iron from their staple diet corn and their habit of cooking foods in iron pots.

18. 3. Hemochromatosis
a. This is a rare disease in which iron is directly deposited in the tissues (liver, spleen, pancreas and skin).
b. Hemosiderosis is sometimes accompanied by hemochromatosis.
c. Bronzed-pigmentation of the skin, cirrhosis of liver, pancreatic fibrosis are the manifestations of this
disorder.
d. Hemochromatosis causes a condition known as bronze diabetes

19. Dietary intake of iron
 Adult man — 10 mg/day
 Menstruating woman — 18 mg/day
 Pregnant and lactating woman — 40 mg/day

20. Summary
 The total content of iron in an adult body is 3-5 g.
 About 70% of this occurs in the erythrocytes of blood as a constituent of hemoglobin.
 Heme is the most predominant iron-containing substance. It is a constituent of several proteins/enzymes.
 Iron is mainly absorbed in the stomach and duodenum. In normal people, about 10% of dietary iron is usually
absorbed.
 Iron in the ferrous form is soluble and readily absorbed.
 There are several factors which may interfere with the absorption of iron.
 Iron in plasma is transferred by Transferrin molecules. ). Each transferrin molecule can bind with two atoms of ferric
iron (Fe 3+ ). The plasma transferrin (concentration 250 mg/dl) can bind with 400 mg of iron/dl plasma. This is
known as total iron binding capacity (TIBC) of plasma.
 Iron is stored in liver, spleen and bone marrow in the form of ferritin (a temporary storage molecule). Hemosiderin
is another iron storage protein.
 Iron metabolism is one way pathway.
 Some disease states are – 1. Iron deficiency anemia 2. Hemosiderosis 3. Hemochromatosis
 Dietary intake may vary with age and gender of an individual.

21. References
 Class notes
 Biochemistry by MD Rafi
 Satyanarayan’s Biochemistry
 Internet sources