normal iron physiology

1. NORMAL
IRON PHYSIOLOGY
NIKHIL GUPTA
MBBS - 2011

2. SOURCES OF IRON
Heme iron :-
• Liver
• Meat
• Poultry
• Fish
Non Heme iron:-
• Leafy vegetables
• Legumes
• Beans
• Cereals
• Milk

3. DAILY REQUIREMENT
 Children (ages 1-10): 7 to 10 mg per day.
 Women (ages 19-50): 18 mg per day.
 Pregnant Women: 27 mg per day.
 Lactating Women: 9 to 10 mg per day.
 Men (ages 19 and older): 8 mg per day

4. DISTRIBUTION
Total body iron = 3 to 5 grams
• 60 to 70 % - Hemoglobin.
• 15 to 30 % - stored in liver and RE system as
ferritin and hemosiderin.
• 4 % - Myoglobin.
• 0.1 % - Blood plasma as transferrin.

5. .

6. ROLE OF IRON IN THE BODY
• Hematopoiesis.
• Found in Hemoglobin and myoglobin.
• Cytochrome P450 superfamily and catalase, which
metabolize drugs and degrade hydrogen peroxide.
• Conversion of blood sugar to energy.
• Production of enzymes ,new cells, amino acids,
hormones and neurotransmitters.
• Proper immune system functioning.
• Physical and mental growth.

7. ABSORPTION
• 1-2 mg absorbed daily.
• From duodenum and upper jejunum.
• Heme iron is better absorbed than non heme iron.
• Ferric Iron(III) is reduced to ferrous iron(II) by
D cyt-b (duodenal cytochrome b).
• Taken up through the DMT1 (divalent metal
transporter 1) protein.
• Heme iron is taken up through the Heme
Transporter.

8. • Once in the enterocytes, iron is exported through
the membrane protein ferroportin 1 into the
plasma.
• Some of it can be stored as ferritin ,depending on
the current iron requirement of the body.
• Iron(II) in the plasma is immediately oxidised to
iron(III) by hephaestin or ceruloplasmin.
• The iron(III) binds to transferrin and is transported
with the blood stream to the target cells for
utilization.

10. Control of iron absorption
Mucosal block theory

11. FACTORS AFFECTING
ABSORPTION
Enhancers:-
• Vitamin C
• Cooking in iron
vessels
• Gastric acid
• Cysteine
• Sugar
• Amino acid
• Lactate
• Pyruvate
Inhibitors:-
• Tannins
• Phosphates
• Oxalates
• Pancreatic secretions
• Antacids
• Calcium
• Tetracyclines

12. UTILIZATION
• Attachment of iron-transferrin complex to specific
Transferrin receptors TfRs on RBCs and other cells.
• Complex engulfed by endocytosis.
• Iron dissociates from complex at acidic pH of
endosomes.
• Released iron is utilized.
• Tf and TfR are returned to cell surface to
carry fresh loads.

14. STORAGE
• In tissues-as ferritin & hemosiderin.
• In blood-as transferrin.
• Excess iron in the blood is deposited
especially in liver hepatocytes & in the
reticulo-endothelial cells of the bone marrow.
This may lead to iron toxicity.

15. EXCRETION
• Daily excretion in adult male = 0.5-1 mg
mainly as exfoliated GI mucosal cells , RBCs
and in bile.
• Very little in urine and sweat.
• In women, additional menstrual loss of
blood may bring iron loss average upto 1.5
mg per day.

16. REGULATION OF IRON
Ferroportin
FP
Hc
LEVELS
• Mediated by hepcidin -
produced by the liver in
response to increased iron
availability or stores.
• Hepcidin downregulates
ferroportin in
enterocytes-blocks iron
absorption from the
intestine.

18. DEFICIENCY OF IRON
CAUSES-
chronic bleeding.
1.excessive menstrual bleeding.
2.GIT bleeding (ulcers, hemorrhoids, Ulcerative
Colitis etc.).
inadequate intake.
substances (in diet or drugs) interfering with
iron absorption.
malabsorption syndromes.
Inflammation.

19. SYMPTOMS
anemia
fatigue
dizziness
pallor
hair loss
irritability
weakness
brittle or grooved nails
glossitis
BRITTLE
GROOVED
NAILS
GLOSSITIS

20. WHEN DOES IRON BECOME A
PROBLEM?
• Normally 3 – 5 g of iron in the body.
• Tissue damage when total body iron is 7 – 15
g.
• 3 commonly encountered forms of chronic
overload:
1- Primary haemochromatosis
2- Transfusion-associated haemochromatosis
3- Dietary causes

21. EFFECTS OF IRON
OVERLOAD
• Cardiac failure
• Liver cirrhosis/fibrosis/cancer
• Diabetes mellitus
• Infertility
• Growth failure

23. 1. Primary Haemochromatosis (chronic iron
toxicity)
• Excessive absorption of iron from the gut
• Iron accumulates in the liver, heart and pancreas &
damages these organs by free radical production
• gives the skin a bronze color
Therapy:
Phlebotomy (removal of 0.5 l of blood): a decrease of
iron in the circulation leads to iron mobilisation from
stores

24. 2. Secondary haemochromatosis
• Due to multiple frequent blood transfusions
• in thalassemia major, sickle cell anaemia
Therapy: iron chelators
3. Dietery causes (Acute iron poisoning)
• among people who are exclusively cooking in iron
pots
• due to ingestion of iron tablets (15-20) - fatal
poisoning in young children.
• Vomiting, diarrhoea, cyanosis, hemetemesis,
convulsions, acidosis, shock, death
Therapy: iron chelator-desferoxamine