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MLT 203 Clinical Chemistry II > Exam 3 Iron/Porphyrin/Trace Elements > Flashcards

Exam 3 Iron/Porphyrin/Trace Elements Flashcards

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1
Q

Distribution & function of iron throughout the body

A
  • Hemoglobin 65% - oxygen delivery
  • Myoglobin 10% - muscle oxygen
  • Bound to enzymes 1-3% - cellular oxidative mechanism
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2
Q

How much iron does the body contain?

A

3-5g

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3
Q

Types of iron

A

• Heme – meats, especially organ meats
• Non-heme – plants & iron-fortified foods
o Spinach, beets, beans, almonds, bran flakes

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4
Q

Where is iron stored?

A

• Stored in bone marrow, spleen, liver

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5
Q

What are the storage forms of iron?

A

• Ferritin – soluble
1. Major iron storage protein found in all cells in body
2. Protein shell surrounding iron core
• Hemosiderin – insoluble
1. Found in cells of liver, spleen, bone marrow

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6
Q

How is iron transported?

A

• Plasma: transferrin

  • Formed in liver
  • Transports Fe3+ from GI tract and delivers to specific receptor sites
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7
Q

Iron RDA - ages 19-50

A

18mg/d

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8
Q

Iron RDA - ages 51+

A

8mg/d

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9
Q

Describe ferrous iron

A

2+

  • absorbed form
  • bound to protein: transferrin
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10
Q

Describe ferric iron

A

3+

  • not easily absorbed
  • dietary form
  • needs to be reduced before it can be absorbed
  • transport & storage form
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11
Q

What causes decreased levels of iron?

A 
• Decreased availability
o	Inadequate intake, malabsorption
• Increased need
o	Growth, premenopausal women, pregnancy
• Chronic loss
o	Peptic ulcer, excessive menstruation, hemorrhoids, gastritis
• Chronic diseases
o	Infections, inflammatory diseases
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12
Q

What causes increased levels of iron?

A

• Increased absorption
o Hemochromatosis, medication/iron supplements, dietary intake, transfusion
• Increased RBC destruction
• Disease
o Lead poisoning, pernicious anemia, megaloblastic anemia

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13
Q

What causes iron deficiency anemia?

A

Blood loss, inadequate intake, malabsorption

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14
Q

Describe transferrin, % saturation, and ferritin in IDA

A

Transferrin - increased
% saturation - decreased
Ferritin - <10ng/mL typical

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15
Q

Who is affected by IDA?

A

Children, women, pregnant women

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16
Q

What is hemosiderosis?

A

Secondary/acquired iron accumulation

No tissue damage, reversible

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17
Q

What causes hemosiderosis?

A

Iron supplements, blood transfusions

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18
Q

What is hemochromatosis?

A
  • Hereditary disorder: mutation in HFE gene
  • Iron accumulates in tissues leading to organ failure
  • Irreversible
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19
Q

Symptoms of hemochromatosis

A
  • Diabetes mellitus
  • Bronzing of skin
  • Sexual dysfunction
  • Fatigue, weakness
  • Manifests in middle age
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20
Q

What is a total iron test?

A

Reflects amount of ferric Fe3+ iron bound to transferrin

- Does not include free iron found in hemoglobin

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21
Q

What is TIBC test?

A

Amount of iron that could be bound if transferrin were saturated
- Typically, 1/3 of iron-binding sites are saturated

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22
Q

What is % saturation?

A

Transferrin saturation

- Normal range 15-50%

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23
Q

What is transferrin?

A

Negative-acute phase reactant

  • Useful to diagnose hypo chromic anemias
  • Measured by the amount of iron it can bind
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24
Q

What is ferritin?

A

Best diagnostic test for IDA

  • Reflects iron stores
  • Serves as acute-phase reactant
  • Patients with inflammation or chronic infection may have increased ferritin
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25
Q

Specimen requirements for iron studies

A
  • Serum or plasma with heparin
  • Oxalate, citrate, or EDTA binds Fe ions
  • Early morning sample preferred due to diurnal variation (highest am)
  • No hemolysis
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26
Q

Test methodology for iron

A

Colorimetric

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27
Q

Iron reference range - men

A

65-175 ug/dL

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28
Q

Iron reference range - women

A

50-170 ug/dL

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29
Q

Transferrin reference range

A

200-360 mg/dL

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30
Q

Ferritin reference range - male

A

20-250 ng/mL

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31
Q

Ferritin reference range - female

A

10-120 ng/mL

32
Q

TIBC reference range

A

250-425 ug/dL

33
Q

Calculation for TIBC

A

TIBC = Iron + UIBC (unsaturated iron binding capacity)

34
Q

Calculation for transferrin

A

Transferrin mg/dL = TIBC x 0.70

35
Q

Calculation for % saturation

A

% sat = (total iron/TIBC) x 100

36
Q

What is decreased in IDA?

A

 Iron, ferritin, % saturation

37
Q

What is increased in IDA?

A

Transferrin, TIBC

38
Q

What is increased in iron overdose?

A

iron, ferritin, % saturation

39
Q

What is decreased in iron overdose?

A

transferrin, TIBC

40
Q

What is increased in hemochromatosis?

A

Iron, ferritin, % saturation

41
Q

What is decreased in hemochromatosis?

A

transferrin, TIBC

42
Q

What is decreased in malnutrition?

A

iron, transferrin, ferritin, TIBC

- % sat. variable

43
Q

What is decreased in chronic anemia?

A

iron, transferrin, % saturation, TIBC

44
Q

What is increased in chronic anemia?

A

ferritin

45
Q

What is increased in acute liver disease?

A

iron, ferritin, % saturation

- TIBC, transferrin variable

46
Q

Describe the structure & function for porphyrins

A
  • Chemical intermediates in the synthesis of hemoglobin, myoglobin, & various enzymes
  • Made up of four pyrrole rings
47
Q

Where are porphyrins synthesized?

A

Bone marrow & liver

- Synthesis occurs in mitochondria/cytoplasm

48
Q

What is hemoglobin made of?

A

4 heme + 4 polypeptide chains

49
Q

What is myoglobin made of?

A

1 heme + 1 polypeptide chain

50
Q

What are porphyrias?

A

• Disorder of porphyrin metabolism

  • Inherited: rare
  • Acquired: lead
51
Q

Symptoms of porphyrias

A
  • port wine colored urine
  • cutaneous photosensitivity
  • itchy skin
  • hyperpigmentation
  • inflammatory reaction occurs on exposure to UV light
  • neurologic abnormalities
52
Q

What is uroporphyrin found?

A

urine

53
Q

Where is coproporphyrin found?

A

urine & feces

54
Q

Where is protoporphyrin found?

A

feces

55
Q

Specimen requirements for porphyrins

A 
•	Protect specimens from light
•	Blood – whole blood & plasma
•	Test methods:
	Urinary porphobilinogen (PBG)
	Urinary aminolevulinic acid (ALA)
	Urinary porphyrins
56
Q

What does lead interfere with?

A
  • Interferes with heme synthesis

* Inhibits ALA dehydrates and ferrochelatase

57
Q

Final storage site for lead?

A

Bone 95%

58
Q

Specimen requirements for lead

A

• Whole blood
 Circulating lead found in RBCs
o Royal blue top with EDTA anticoagulant
o Lead free collection tubes

59
Q

ULN for lead, children

A

<10 ug/dL

60
Q

ULN for lead, adults

A

<25 ug/dL

61
Q

Symptoms of lead exposure

A

 Headaches, clumsiness, seizures, hyperactivity, ADHD, decreased IQ, abdominal pain, anemia
 Basophilic stippling

62
Q

What are essential trace elements?

A

considered essential if a deficiency impairs a biochemical or functional process

63
Q

Examples of essential trace elements

A

Iron, copper, zinc, selenium, chromium, manganese

64
Q

Function of copper

A

Critical for iron reduction in heme synthesis pathway

65
Q

Causes & consequences of copper deficiency

A
  • Malnutrition
  • Malabsorption
  • Neutropenia & hypochromic anemia
  • Osteoporosis
  • Decreased pigmentation of skin
66
Q

What is Menkes disease?

A

Genetic disease that results in extreme deficiency of copper

67
Q

What is Wilson’s disease?

A

Genetic disease that results in copper toxicity

- Kayser-Fleischer rings

68
Q

Function of zinc

A
  • Influences more than 300 enzymes

- Synthesis & metabolism of proteins, glycolysis, cholesterol metabolism

69
Q

Consequences of zinc deficiency

A
  • Causes growth retardation
  • Slow skeletal maturation
  • Testicular atrophy
70
Q

Toxicity of zinc

A
  • GI tract symptoms

- decreased heme synthesis

71
Q

Where is aluminum found?

A

antacids, astringents, buffered aspirin

72
Q

Symptoms of aluminum toxicity

A

gait disturbances, seizures, dementia, bone disease, anemia

73
Q

Where is arsenic found?

A

environmental/occupational exposure

74
Q

Symptom of increased arsenic

A

Increased frequency of skin cancer

75
Q

Where is cadmium found?

A

inhaled in tobacco smoke, ingested in food, airborne exposure

76
Q

Symptoms of increased cadmium

A

o Chronic exposure – renal dysfunction
o Breathing vapors – nasal epithelial & lung damage
o Nausea, vomiting, abdominal pain

77
Q

Symptoms of increased mercury

A

headache, tremors, cramps, diarrhea, impaired coordination, dermatitis, proteinuria, hepatic dysfunction

MLT 203 Clinical Chemistry II (3 decks)

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