How does elevated unconjugated bilirubin cause jaundice? - USMLE Forums
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Old 06-15-2011
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Question How does elevated unconjugated bilirubin cause jaundice?

I can't figure out how an elevation of unconjugated bilirubin results in clinical apparent jaundice (yellow discoloration of skin). Unconjugated bilirubin is hydrophobic and bound to albumin(this is why it is not excreted in urine).how does it get out to tissues? Does anyone know what is the proportional rate of unconjugated bilirubin bound to albumin( is it 100% or a little percent is free and in balance with albumin bound bilirubin)?
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Old 06-15-2011
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Default Its the color of the blood

It does not need to be free or go out into tissues. The mere present of bilirubin in the blood is enough to turn the skin color into yellow.
The color of your skin is partially determined by the color of your blood in the tiny skin capillaries.
That's how you get blue color in cyanosis, pale color in anemia, yellow color in jaundice, ....
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Old 08-05-2011
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Hello friends,

Large amounts of bilirubin in the blood can lead to jaundice. Jaundice is a yellow color in the skin, mucus membranes, or eyes.
Jaundice is the most common reason to check bilirubin levels.
  • Most newborns have some jaundice. The doctor or nurse will often check the newborn's bilirubin level. See: Newborn jaundice
  • The test may also be done in older infants, children, and adults who develop jaundice.
source : nlm.nih.gov/medlineplus/ency/article/003479.htm
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Old 08-05-2011
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Quote:
Originally Posted by kalampakas View Post
I can't figure out how an elevation of unconjugated bilirubin results in clinical apparent jaundice (yellow discoloration of skin). Unconjugated bilirubin is hydrophobic and bound to albumin(this is why it is not excreted in urine).how does it get out to tissues? Does anyone know what is the proportional rate of unconjugated bilirubin bound to albumin( is it 100% or a little percent is free and in balance with albumin bound bilirubin)?
thanks
Most of binding that occurs on plasma proteins is at 33% (1/3 of sites), never 100%. So when the sheer amount of unconjugated bilirubin increases, or you have an decrease in binding protein, free unbound unconjugated biliribun goes up, "golden" value is >2 mg/dl for it to show as jaundice.
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