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NHM 561 > Iron Part II > Flashcards

Iron Part II Flashcards

1
Q

Iron is present as a part of heme in which 3 heme proteins?

A
  1. Hemoglobin
  2. Myoglobin
  3. Cytochromes (located in ETC)
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2
Q

(TRUE/FALSE)

In hemoglobin/myoglobin, iron can form a loose bond with oxygen.

A

TRUE.

Hemoglobin will directly bind to oxygen, allowing us to transport it from the lungs to the peripheral tissue

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3
Q

What does hemoglobin do?

A

Allows oxygen transport from the lungs to tissue

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3
Q

What does myoglobin do?

A

Allows for the transitional storage of oxygen in muscle

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4
Q

What do cytochromes do?

A

Allows for the transport of electrons through the respiratory chain, which is important for us to generate ATP

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5
Q

Where is hemoglobin synthesized?

A

in RBCs

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6
Q

What % of total oxygen is found in blood?

A

~98.5%

RBCs also pick-up CO2 from the tissue and transport the CO2 to the lungs to be exhaled

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7
Q

How many hemoglobin molecules do a RBC contain?

A

Millions of hemoglobin

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8
Q

How much of our total body iron is stored in RBCs?

A

~65%

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9
Q

What is the structure of hemoglobin?

A

4 heme & 4 globin chains

These form 2 dimers and the molecule itself is referred to as a quaternary structure

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10
Q

What is the structure of myoglobin?

A

Single heme & single globin chain

(therefore, the oxygen capacity is greatly diminished because there is only one chain and it can only bind 1 molecule of oxygen)

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11
Q

Where is myoglobin found?

A

Present ONLY in muscles (heart & skeletal muscle)

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12
Q

How much of our total body iron is found in myoglobin?

A

~10%

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13
Q

What is the function of myoglobin?

A

Transports and stores oxygen within muscles and releases O2 to meet increased metabolic needs during muscle contraction

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14
Q

Where are cytochromes located?

A

within the membrane of the ETC

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15
Q

What is the function of cytochromes?

A

Cytochrome b and c pass along single electrons

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16
Q

Cytochrome P450 of enzymes

A

Functions in a similar manner within the liver, which requires iron to function

It is involved in drug metabolism and steroid hormone synthesis

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17
Q

What are some iron-containing enzymes?

A

These enzymes require iron for the reactions to occur

NADH dehydrogenase
Succinate dehydrogenase
Monooxygenases
Dioxygenases

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18
Q

Who is at the greatest risk for iron deficiency?

A

Older infants
Young children
Women of child bearing age

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19
Q

How many people worldwide have iron deficiency?

A

2 to 5 billion

~700 million with iron deficiency anemia

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20
Q

In developing countries, XXXXX of all children and women of childbearing age suffer from iron deficiency anemia, versus the US?

A

1/3 in developing countries

9% of children between 1-2 y/o
12% pregnant women
11% females 16-49 y/o

21
Q

Define iron deficiency.

A

DEPLETED STORES without regard to the degree of depletion or to the presence of anemia

Individuals can be iron deficient, without being anemic

22
Q

Define iron deficiency anemia.

A

SEVERE DEPLETION of iron stores that result in a LOW HEMOGLOBIN CONCENTRATION

RBCs are pale, microcytic, and cannot carry enough oxygen to the tissues

23
Q

Explain clinical characteristics of IRON OVERLOAD.

A

Occurs a lot with children, who have taken MVIs w/ iron in high doses.

HIGH FERRITIN
VERY HIGH TRANSFERRIN SATURATION
ALL other variables are normal

24
Q

Explain the clinical characteristics of NORMAL IRON STATUS.

A

All normal

25
Q

Explain the clinical characteristics of DEPLETED IRON STORES.

A

FIRST STAGE of iron deficiency occurs very early on, such that maybe dietary intake has declined significantly and recently.

DECREASED FERRITIN
DECREASED HEMOSIDERIN

26
Q

What is the compensatory response for depleted iron stores (first stage)?

A

An increase in iron absorption that often prevents progression to more severe stages of iron deficiency.

This stage is NOT associated with adverse physiological consequences, but does represent increased vulnerability from a long-term marginal iron balance, that might progress to a more severe deficiency.

27
Q

What is the earliest indicator of iron status?

A

[FERRITIN]

All other values remain NORMAL because remember- we have iron stores (intercellular ferritin and hemosiderin) which we store within our cells so this will keep the other markers in the normal range temporarily.

28
Q

Explain the clinical consequences of a DECREASE IN TRANSPORT IRON (2nd stage).

A

SECOND STAGE of iron deficiency

DECREASE [FERRITIN]
DECREASE TRANSFERRIN SATURATION
INCREASE ERYTHROCYTE PROTOPORPHYRIN (As the RBCs will take this protoporphyrin and use it to synthesize heme, this increases because there is NOT enough iron to make the heme, so this PRECURSOR will back up)

NORMAL MCV
NORMAL HEMOGLOBIN (so the individual is not experiencing any severe symptoms at this point)

29
Q

Explain the clinical characteristics of IRON DEFICIENCY ANEMIA (3rd stage).

A

Characterized by decreased functional iron (decreased levels of HB)

BIG DECREASE IN [FERRITIN]
DECREASE IN TRANSFERRIN SATURATION

BIG INCREASE IN ERYTHROCYTE PROTOPORPHYRIN
DECREASE IN MCV
DECREASE IN HEMOGLOBIN**’

29
Q

Explain the clinical characteristics of IRON DEFICIENCY ANEMIA (3rd stage).

A

Characterized by decreased functional iron (decreased levels of HB)

BIG DECREASE IN [FERRITIN]
DECREASE IN TRANSFERRIN SATURATION

BIG INCREASE IN ERYTHROCYTE PROTOPORHINE

30
Q

What hemoglobin level would indicate severe iron deficiency anema?

A

Hemoglobin less than 70 g/L (<7 g/dL)

31
Q

In the US, why are most cases of iron deficiency anemia among children and women mild?

A

Due to better access to healthcare compared to developing countries, which may result in it progressing further to a severe case.

32
Q

Why are children greater than 6 months of age and young children at higher risk for iron deficiency?

A

Depletion of iron stores (d/t growth spurts)

The low iron content of most infant diet

Early feeding of cow’s milk can promote increased GI blood loss

33
Q

What 2 factors predispose women to iron deficiency anemia?

A
  1. Menorrhagia (> 80 ml/month menstruation)
  2. Pregnancy
34
Q

Why does pregnancy predispose women to iron deficiency anemia?

A
  1. Increase iron requirements to supply the expanding blood volume of the mother and the rapidly growing fetus and placenta
  2. The total iron required during pregnancy averages 1g, thus exceeding the amount of storage iron available to most women (~0.3 g).
35
Q

(TRUE/FALSE)

Infant formula in the US is fortified with iron

A

TRUE

36
Q

What causes iron deficiency anemia in the ELDERLY?

A

More commonly associated with chronic inflammatory conditions, such as arthritis

37
Q

(TRUE/FALSE)

GI blood loss may occur without notice and it can be from chronic use of drugs (aspirin) or lesions or tumors.

A

TRUE

Iron deficiency anemia can result from GI blood loss, irrelevant of their iron dietary intakes

38
Q

Explain the process of chronic inflammatory conditions and iron deficiency anemia in the elderly.

A

This is partly a protective mechanism. The response to chronic inflammation will be that HEPHAESTIN (hormone) will be released in large amounts from the liver. There has been a lot of data accumulated over the years that high iron in the blood can be used by microorganisms (for growth), so resulting in an increased risk for infections. So, one way the body shuts this down is that it will down-regulate the body’s ability to absorb iron via the HEPAHESTIN hormone.

HEPHAESTIN will go to the basolateral membrane (remember- its job is to block ferroportin) preventing iron from being pumped from the enterocyte across to where it can attach to transferrin.

39
Q

In children, when do impaired mental development, reduced attention, and poor learning performance happen?

A

When HEMOGLOBIN levels are lower than 10 g/dL at 5 years of age

40
Q

In adults, when does the substantial reduction in WORK CAPACITY occur?

A

When HEMOGLOBIN concentration falls below 100 g/L (10 g/dL)

Impaired psychomotor development, intellectual performance, and changes in behavior can result as well. This is due to a decrease in oxygen perfusion to the brain and some of the CNS

41
Q

(TRUE/FALSE)

Even a mild degree of anemia can decrease performance during brief but intense exercise.

A

TRUE

Due to that reduced oxygen perfusion to the tissue

42
Q

What is the best treatment for iron deficiency?

A

FERROUS SULFATE is the least expensive and most widely used form of oral supplementation

Recommended dose: 60 mg elemental iron per day for adults

For: 2-3 months until iron levels are restored and indicators are WNL

43
Q

How long does it take after treatment to see a response?

A

After 1 month, when the deficiency in hemoglobin is partially corrected, usually with a rise > 100 g/L. Iron treatment is continued for another 2-3 months.

44
Q

Why is acute toxicity or iron poisoning, a concern?

A

Can lead to severe organ damage and death within hours or days

Occurs mainly among young children

Remember: Iron is VERY REACTIVE and PRO-OXIDATIVE, if it is NOT bound up to a protein and chaperoned throughout the body.

45
Q

Define iron overload.

A

Nonspecific term for increased total body iron content with or without organ damage

46
Q

Define hemosiderosis.

A

Results from increased iron stores in the form of hemosiderin

47
Q

Define hemochromatosis.

A

Excessive storage of iron that causes organ damage;

A genetic defect resulting in the inability of the intestinal cells to accurately sense iron stores, resulting in high iron absorption

Caucasian males

48
Q

What plasma ferritin concentration would indicate iron deficiency?

A

Less than 12 ng/mL

NHM 561 (21 decks)

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