Iron in Health and Disease

Question 1

Why can iron be dangerous?

Answer 1

It causes oxidative stress and produces free radicals

Question 2

The majority of body iron can be found within where?

Answer 2

Within the haem group, in globulin chains. The Fe2+ ion sits specifically within the porphyrin ring

Question 3

Where is Hb synthesised? What two components are needed to form haem?

Answer 3

In the cytoplasm of immature blood cells / protoporphyrin and Fe2+

Question 4

What is the rate of a) iron absorption? b) iron loss? / what is the significance of this?

Answer 4

a) 1mg/day b) 1mg/day / keeps a constant level of iron in the body

Question 5

When iron is absorbed, it is taken into the plasma. From the plasma, it can travel to where?

Answer 5

The parenchymal tissues (predominantly the liver) to be stored, or to the erythroid marrow to make haem

Question 6

When red cells are broken down, where is iron taken into to be taken back to the plasma?

Answer 6

Macrophage stores

Question 7

All iron in the plasma is bound to what molecule? This iron in the plasma acts as what?

Answer 7

Transferrin / available iron

Question 8

Iron absorption occurs mainly where? Therefore it is absorbed into where?

Answer 8

The duodenum / epithelial cells of the duodenal mucosa

Question 9

What are some factors which enhance iron absorption?

Answer 9

Ascorbic acid and alcohol

Question 10

What are some factors which decrease iron absorption?

Answer 10

Tannins, Ca++, PPI drugs

Question 11

Which iron state is more readily absorbed?

Answer 11

Fe2+

Question 12

What is the first molecule involved in the absorption of iron, which is found in the duodenal luminal surface? What is its function?

Answer 12

Duodenal cytochrome B - reduces the ferric ion (Fe3+) to the ferrous ion (Fe2+)

Question 13

What is the role of divalent metal transporter 1 in the absorption of iron?

Answer 13

Transports ferrous iron from the duodenal lumen to the duodenal enterocyte

Question 14

What is the role of ferroportin in iron absorption?

Answer 14

Facilitates iron export from cells and passes it onto transferrin for transport elsewhere

Question 15

Iron absorption is mainly regulated by which molecule? Where is most of this produced? In response to what?

Answer 15

Hepcidin / liver / iron load and inflammation

Question 16

How does hepcidin negatively regulate iron uptake?

Answer 16

It binds to ferroportin and causes its degradation so that iron is ‘trapped’ inside macrophages and duodenal enterocytes

Question 17

The liver is the main sensor of iron. If there is plentiful iron, what will it do?

Answer 17

Produce hepcidin to downregulate ferroportin

Question 18

The liver is the main sensor of iron. If there is iron deficiency, what will it do?

Answer 18

Inhibit hepcidin production to upregulate ferroportin

Question 19

What is transferrin?

Answer 19

A protein with two binding sites for iron atoms in the Fe3+ state

Question 20

What is the role of transferrin?

Answer 20

Transports iron from donor tissues (e.g. macrophages, duodenal intestinal cells and hepatocytes) to cells expressing transferrin receptors (mainly the erythroid marrow)

Question 21

Describe what is meant by each of the following terms: a) holotransferrin? b) apotransferrin?

Answer 21

a) transferrin bound to iron b) transferrin not bound to iron

Question 22

What happens to transferrin saturation if someone is in iron overload?

Answer 22

Increase

Question 23

What happens to transferrin saturation if someone is iron deficienct?

Answer 23

Decrease

Question 24

What is ferritin?

Answer 24

A spherical intracellular protein which stores up to 4000 Fe3+ ions

Question 25

A tiny amount of serum ferritin reflects the intracellular ferritin synthesis which acts as an indirect measure of what?

Answer 25

Storage iron

Question 26

What are some other factors (aside from excess iron) which can cause serum ferritin levels to rise?

Answer 26

It is an acute phase protein so can be risen in infection or malignancy

Question 27

What happens to serum ferritin in iron deficiency?

Answer 27

Decreased

Question 28

What happens to serum ferritin in iron overload?

Answer 28

Increased

Question 29

In terms of assessment of iron status, what is used as a measure of functional iron?

Answer 29

Hb concentration

Question 30

In terms of assessment of iron status, what is used as a measure of transport iron?

Answer 30

% saturation of transferrin with iron

Question 31

In terms of assessment of iron status, what is used as a measure of storage iron?

Answer 31

Serum ferritin (and also tissue biopsy but this is rarely indicated)