Important Liver Values: Albumin, ALT, ALP & AST

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  • 0:03 Different Ways to…
  • 0:26 The Albumin Clue
  • 1:28 Using AST and ALT as a Clue
  • 3:13 Using ALP as a Clue
  • 6:00 Important Parting Notes
  • 7:06 Lesson Summary
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Lesson Transcript
Instructor: Artem Cheprasov

Artem has a doctor of veterinary medicine degree.

This lesson will discuss three important enzymes that indicate liver or biliary tree issues. They are ALT, ALP, and AST. We'll talk about some of the reasons why they may be elevated.

Different Ways to Measure Injury

If you injure yourself, then you'll be able to describe that you were hurt through numerous ways. Those are all signals or cues that you are hurt and need to do something about it.

In medicine, we use more than one clue that tells us that the liver, an important organ in our body, is hurting and that we must do something about it in order to improve our health. That's what this lesson will be discussing.

The Albumin Clue

The liver is a big manufacturing plant that produces a lot of stuff. One important thing it makes is a protein called albumin. Albumin is responsible for transporting certain medicines you might have to take, waste products, and hormones. As if that wasn't important enough, if there was no albumin, you'd also look very swollen because albumin's presence in the blood keeps fluid from leaving your blood vessels and into your tissues.

Albumin is like a sponge; it sucks in water and keeps it in the blood vessels. And just like a sponge can carry all sorts of little microscopic particles within it, like minerals, bacteria, and the like, so too does albumin carry the things I mentioned before.

If abnormally low amounts of albumin are found in the blood, something termed hypoalbuminemia, then this can clue us into the fact that some sort of severe or long-standing liver damage has occurred, resulting in decreased albumin production.

Using AST and ALT as a Clue

Of course, a factory, our liver, that's in trouble throws us more than one clue that something is wrong. Decreased manufacturing capabilities, resulting in low albumin, is just one clue that the factory isn't working properly. But factories use machines, furnaces, and people to convert a raw material into a finished product. If something goes wrong with the machines, furnaces, or people, then smoke, fire, and loud screams may come from our factory to indicate a problem.

The machines, furnaces, and people in the liver are known as enzymes, proteins that speed up biochemical reactions. If the liver is sick, then it releases these enzymes into the bloodstream in larger-than-normal quantities. Their levels, these signals of liver injury, can then be measured with blood tests. If they are elevated, they may indicate primary liver disease, such as cirrhosis, hepatic congestion, or hepatitis.

Two of these enzymes that are measured for this purpose are AST, aspartate aminotransferase, and ALT, alanine aminotransferase, both of which have normal blood values of approximately 0-35 U/L. Also, AST was known as SGOT, and ALT used to be called SGPT. I decided to let you know that just in case you decided to read a medical text from the 1970s - then you'll know what those things mean in modern terms or in certain countries that still use those abbreviations. But just remember AST and ALT for our lesson.

Using ALP as a Clue

Other than AST and ALT, there is an enzyme called ALP, technically called alkaline phosphatase, whose normal range in the blood is approximately 30-120 U/L. Sometimes it's colloquially called 'alk phos' between medical personnel. It's much easier to say it that way since it's shorter than saying alkaline phosphatase and doesn't get confused with other abbreviations phonetically like ALP may be when pronounced really quickly.

Elevations in alk phos are associated with biliary tree (aka biliary tract) obstruction. Knowing this, you should use our medical slang, alk phos, to your advantage. Think of the 'o' in alk ph'o's as an indicator of 'o'bstruction.

If you weren't aware already, bile is a fluid that helps to digest fat. It is produced by the liver cells, known as hepatocytes. Once they produce bile, they secrete this bile into a system of channels and ducts, termed the biliary tree, which eventually empties out into the small intestine's duodenum. Anything that obstructs this outflow or hepatocyte secretion of bile results in improper outflow of bile from the liver, something known as cholestasis. Therefore, alk phos is an indicator of this cholestasis.

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