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Question Percentage of Iron Saturation?

how does % iron saturation changes in anemia of chronic disease ?
Goljan rr-decrease
FA 2010-no change

Which one is more credible ?


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in anemia of chronic disease, the only thing that increases is ferritin.
so just think of it as everything else decreases.

makes sense for %sat to decrease also because theres less iron available so theres less saturation.
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But due to increase in ferritin there is decrease in TIBC
Decrease in serum iron/decrease in TIBC=?


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Quote:
Originally Posted by MedicalExaminer View Post
But due to increase in ferritin there is decrease in TIBC
Decrease in serum iron/decrease in TIBC=?


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yea, thats correct.
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It could be either. In chronic disease, you can see normal TIBC/saturation or increased TIBC/decreased saturation. I think Goljan and Pathoma both say this in their lectures.

In anemia of chronic disease, there are two main reasons for the anemia, both of which are caused by increased concentrations of hepcidin, an acute phase reactant. One problem is decreased absorption of iron and the other is increased sequestration. If the problem is primarily sequestration, then you still have iron being carried in the blood, and as a result, TIBC is normal. If the problem is primarily absorption, then you have a classic iron deficiency anemia with low saturation and high TIBC. In most cases, you have a mixed picture... so your saturation might be slightly decreased, but still in the normal range.

So the bottom-line high-yield point is that it can go either way.
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Quote:
Originally Posted by MedicalExaminer View Post
how does % iron saturation changes in anemia of chronic disease ?
Goljan rr-decrease
FA 2010-no change

Which one is more credible ?
Anemia of Chronic disease is due to iron being trapped in the macrophages. There are two mechanisms - both due to two acute phase reactants

1) IL 6 --> it causes enhanced liver production of hepcidin which then blocks the transport of iron out of macrophages and results in decreased circulating iron.
2) IL 1 --> increases lactoferrin which also traps the inron in bone marrow macrophages.

In both cases, you have increased ferritin (stored iron) and decreased circulating iron, % saturation and decreased TIBC. TIBC is total iron binding capacity .. if the total iron is increased (due to increased ferritin) but its not in circulation and therefore cannot be bound, it results in decreased total iron binding capacity.
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I mean from equation
Serum iron/tibc x 100 = % saturation

If both decrease how come % saturation decreases ?



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If serum iron decreases more than TIBC, then the (serum iron)/(TIBC) ratio will go down.
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Quote:
Originally Posted by MedicalExaminer View Post
I mean from equation
Serum iron/tibc x 100 = % saturation

If both decrease how come % saturation decreases ?
Here's what I think it is:

TIBC = measure of transferrin in the serum.

For every 3 molecules of transferrin, only one is bound to iron. So when your serum iron goes down the tibc doesnt decrease as much as compared to serum iron. That causes the %saturation to decrease because even less iron is now bound to transferrin.
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I think another reason is because your serum ferritin goes up, the liver says "whoa hold on a second, theres too much iron, i better decrease the transferrin levels in blood or too much of it is going to be bound"

so the liver actually releases less transferrin

-ferritin and tibc ..always go in opposite direction.
-serum iron and % saturation .. always go in same direction.
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Quote:
Originally Posted by Hope2Pass View Post
-serum iron and % saturation .. always go in same direction.

Thatīs not always true. In chronic inflammation or neoplastic diseases, decreased transferrin synthesis resulting in its reduced levels. This would result in decreased serum iron as well as TIBC, ultimately leaving %saturation unaffected.
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Quote:
Originally Posted by MedicalExaminer View Post
how does % iron saturation changes in anemia of chronic disease ?
Goljan rr-decrease
FA 2010-no change

Which one is more credible ?


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Both possibilities are true and are equally credible, except that they should specify dual possibilities. As I mentioned in above post % saturation can remain unaffected or another scenario, where TIBC remain unaltered and serum iron and percentage saturation are driven by iron deficiency status.
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