Lectures 10 and 11 - Iron

Question 1

what is the most important factor effecting bioavailability or iron

Answer 1

iron status

Question 2

how does pregnancy affect iron absorption

Answer 2

increases

Question 3

how does recent iron intake affect iron absorption

Answer 3

the mucosal iron block = large amount of iron will decrease absorption of iron you consume after this

Question 4

what is the relative absorption of haem iron

Answer 4

~25-30%

Question 5

what is the relative absorption of non heam iron

Answer 5

~5-15%

Question 6

what are the enhancers of iron absorption

Answer 6

vitamin C and flesh meats (meat, fish, poultry factor)

Question 7

what are inhibitors of iron absorption

Answer 7

phytate, tannins and oxalic acid

Question 8

how is heme iron absorbed and what happens when it is in the enterocyte

Answer 8

heme iron is transported through heme transporter into enterocyte

heme oxygenase reacts with the heme and removes the iron ion from the heme molecule

Question 9

how is non heme iron absorbed and what happens prior to this

Answer 9

non heme iron in the diet is in the Fe3+ form (ferric form)

duodenal cytochrome B reduces the non heme iron from the ferric form (Fe3+) to the ferris form (Fe2+)

the ferris form is the absorbed through the transport of DMT1

Question 10

some iron will be stored as ……… and this will be lost by ….

Answer 10

some iron will be stored as ferratin in the mucosa, which will be lost by shedding of epithelial cells

Question 11

what will transport iron out of the enterocyte

Answer 11

ferroportin

Question 12

ferris form of iron is really reactive so you do not want this floating around in the body, what converts it to Fe3+ before it goes to the rest of the body

Answer 12

hephaestin

Question 13

during high iron intake, what will diferric transferrin bind to in the liver and what will this cause the release of

Answer 13

TfR1 = will then release HFE

Question 14

HFE released from TfR1 will bind to what and what will the stimulate

Answer 14

HFE binds to TfR2 stimulating hepcidin synthesis

Question 15

what does hepcidin bind to and what does this cause

Answer 15

ferroportin on enterocytes and macrophages

• causes hepcidin-ferroportin complex to internalise and be degraded

meaning Fe trapped inside the enterocyte and cant be absorbed into the body

Question 16

~67% body Fe is in the form of

Answer 16

haemoglobin

Question 17

~4% of body Fe is in the form of

Answer 17

myoglobin

Question 18

~0.2% of body Fe is for enzymes involved in ….

Answer 18

• energy metabolism
• neurotransmitter formation
• bacterial killing leukocytes

Question 19

what are the two forms of storage Fe (which is the efficient way and what is not as effective)

Answer 19

• ferritin = most effective way of storage
• haemosiderin

Question 20

how is iron excretion controlled in the body

Answer 20

there is no controlled excretion of iron from the body

Question 21

what are the ways the body loses iron

Answer 21

epithelial cells

fluids

Question 22

formation of erythrocytes requires how much iron

Answer 22

~30mg Fe/day

Question 23

how does majority of iron reutilisation occur

Answer 23

majority from breakdown old red blood cells by macrophages in spleen and liver

Question 24

what is the difference of iron deficiency anaemia and depletion of iron stores

Answer 24

iron deficiency anaemia affects the haemoglobin levels

Question 25

symptoms of iron deficiency anaemia

Answer 25

• decreased growth
• behavioural disturbance
• decreased cognitive function
• fatigue

etc

Question 26

• how are pre term infants at risk of iron deficiency

Answer 26

haven’t had enough time to accrue their iron stores

Question 27

how are infants are risk of iron deficiency

Answer 27

high growth rate and pretty small appetite

Question 28

what adults are at risk of iron deficiency

Answer 28

• menstruating women
• pregnant women
• blood donors

Question 29

types of iron supplements to help iron deficiency

Answer 29

ferrous sulphate tablet or liquid

Question 30

diet is affective in help non anaemia iron deficiency but not as effective as

Answer 30

supplements

Question 31

what is acute iron toxicity

Answer 31

unintentional overdose iron tablets

Question 32

what is hereditary haemochromatosis and what does this lead to

Answer 32

genetic condition = mutation to the HFE gene

poor control of iron absorption = iron accumulates in liver, pancreas, heart muscle …..

Question 33

“african” iron overload was thought it was to do with intake of beer from cast iron drums but what was it really from

Answer 33

unidentified gene responsible

Question 34

what is the RDI or adult men and women

Answer 34

RDI men : 8mg/day

RDI women : 18mg/day