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MLSCI 262 > 360 - Iron & Bilirubin > Flashcards

360 - Iron & Bilirubin Flashcards

1
Q

The majority of the body’s iron, approximately 94% is distributed in…

A

hemoglobin, ferritin, and hemosiderin

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2
Q

Less than 0.1% of the body’s iron is present in plasma as…

A

transferrin

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3
Q

a plasma protein that transports ferric iron (Fe3+) from one organ to another

A

apotransferrin

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4
Q

Normally, approximately ___ of the iron binding sites of transferrin are occupied by iron

A

1/3

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5
Q

Plasma iron levels are highest in the ___________ and progressively ______ over the day

A

morning; decline

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6
Q

causes of increased serum iron

A

hemochromatosis

iron meds

hormonal contraceptives

aplastic anemia

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7
Q

causes of decreased serum iron

A

IDA

hemorrhage

menstruation

medication

anemia of chronic disease

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8
Q

TIBC

A

total iron binding capacity

  1. serum iron is measured as described
  2. ferric iron (Fe3+) is added in excess to the sample to saturate the binding sites on transferrin

excess iron is removed by either a silica or anion exchange column, or by the addition of magnesium carbonate; serum iron assay performed after to compare to first measurement

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9
Q

increased TIBC

A

IDA

pregnancy

oral contraceptives

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10
Q

decreased TIBC

A

chronic inflammatory disease

malignanacy

hemochromatosis

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11
Q

major storage form of iron

A

ferritin
- acute phase protein
- found in BM, liver, spleen
- detected by immunoassay

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12
Q

increased ferritin

A

malignancies

chronic infections

hemochromatosis

chronic inflammatory diseases (SLE)

hepatitis (eg. viral)

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13
Q

decreased ferritin

A

IDA

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14
Q

where is apotransferrin produced?

A

produced by the liver and carries ferric iron in the blood; the iron/apotransferrin complex is known as transferrin

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15
Q

how can we measure apotransferrin?

A

immunoturbidimetry

immunonephelometry

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16
Q

increased transferrin

A

pregnancy

administration of estrogen

iron deficiency

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17
Q

decreased transferrin

A

negative AP: rxn to inflammation, malignancy

decreased synthesis: chronic liver disease, malnutrition

protein loss: nephrotic syndrome

18
Q

fecal immunochemical testing (FIT)

A

detects hemoglobin in feces
screening test for colorectal cancer
recommended for 50y/o; test every 2 years

19
Q

FIT test reaction

A

monoclonal or polyclonal Ab + Hb => Ab-Ag product

20
Q

a degradation production of heme

A

bilirubin

21
Q

main sources of heme

A

aged red blood cells, myoglobin, cytochromes, and peroxidases

22
Q

how is bilirubin transported in blood

A

bound to albumin

23
Q

what happens to bilirubin in the liver?

A

it is conjugated to produce bilirubin monoglucuronide and diglucuronide

both products excreted into intestine with bile

intestine = bilirubin monoglucuronide is hydrolyzed and reduced to form urobilinogen => may further degraded to urobilin

24
Q

method for measuring total bilirubin

A

diazo method (modified Jendraski-Grof method)

Bilirubin + Diazotized sulfanilic acid -> azobilirubin

25
Q

this is used as an accelerant in diazo method as it frees unconjugated bilirubin from albumin

A

caffeine-benzoate-acetate

26
Q

which wavelength is used to measure bilirubin?

A

530 nm

27
Q

interefernece in measuring bilirubin

A
  • lipemia = false INCREASE
  • hemolysis = false DECREASE
  • exposure to light = false DECREASE
28
Q

Direct spectrophotometry for Unconjugated Bilirubin

A
  • exclusively used for newborn children
  • [bilirubin] directly determined at 454 nm
  • bichromatic measurement is used to eliminate interference from oxyhemoglobin
    > absorbance at 454 nm minus the absorbance at 540 nm equals the true bilirubin absorbance
29
Q

interference of direct spectrophotometry for unconjugated bilirubin

A

carotenoids absorb at 454 nm, but newborn children do not have carotene

30
Q

neonatal jaundice

A
  • immature livers cannot conjugate bilirubin = cannot synthesize proteins
  • HbF = increased catabolism of Hb
  • neonates, intestinal flora not fully developed = conjugated bili does not get reduced to urobilinogen for excretion
  • hemolytic disease of newborns = increased Hb catabolism
  • may be treated with UV light therappy
31
Q

Critical levels of unconjugated bilirubin may cause THIS which can result in brain damage (neonatal jaundice)

A

KERNICTERUS

32
Q

critical balue of total bilirubin in children <30 days old

A

> 300 umol/L

33
Q

pre-hepatic jaundice

A

Hemolytic anemia may produce more bilirubin than the liver can process

34
Q

hepatic jaundice

A

Damage to the hepatocytes, or inherited disorders result in the inability to conjugate or excrete conjugated bilirubin, or inability to take up unconjugated bilirubin for conjugation and excretion

35
Q

post-hepatic jaundice

A

cholestasis
- gallstones, spasms, or neoplasms may prevent bilirubin-glucuronide from reaching the intestine

36
Q

inherited disorders of bilirubin metabolism (hepatic jaundice)

A

Crigler-Najjar Syndrome Type I
“ Type II
Dubin-Johnson Syndrome
Rotor Syndrome
Gilbert Syndrome
Lucey-Driscoll Syndrome

37
Q

Crigler-Najjar Syndrome Type I

A

complete absence of UDP-glucuronyltransferase, resulting in very high concentrations of unconjugated bilirubin

autosomal recessive

Kernicterus results in severe brain damage and usually results in death

38
Q

Crigler-Najjar Syndrome Type II

A

autosomal dominant disorder is the result of a partial deficiency in UDP-glucuronyltransferase. Normal life is expected with phenobarbital administration

39
Q

Dubin-Johnson Syndrome

A
  • autosomal recessive condition with jaundice
  • elevated levels of conjugated bilirubin with only a slight increase in unconjugated bilirubin
  • problem involves the excretion of conjugated bilirubin from the hepatic microsomes into the canaliculi
40
Q

Rotor Syndrome

A

similar to Dubin-Johnson Syndrome.

41
Q

Gilbert Syndrome

A

probably autosomal recessive with mild unconjugated hyperbilirubinemia. No treatment is required

42
Q

Lucey-Driscoll Syndrome

A
  • caused by an inhibitor of bilirubin conjugation
  • unconjugated bilirubin levels are increased
  • occurs in the early neonatal period lasting about 2 -3 weeks post-delivery

MLSCI 262 (21 decks)

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