Alkaline Phospatase

Pril

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I am confused with using alkaline phosphatase as a marker, I understand that it increases with sarcomas of the bone, but I saw a question where it was increased wiht lukemia also and in another tumor of the bone where it was decreased? can anyone help me out?
 

BamaFlip

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As I have always understood it, alkaline phosphatase is a marker enzyme whicn may be elevated with certain diseases of the bone and/or liver. In many cases, it serves as a non-specific tumor marker (as you have mentioned).

The following is an excerpt from the Merck Manual, Chapter 37, Section 4...

"Alkaline phosphatase in serum normally comes from the liver and bone and, during pregnancy, from the placenta. It is present in some tumors (eg, bronchogenic carcinoma which makes its own alkaline phosphatase). Bone growth causes an age-dependent rise in normal values, particularly in children < 2 yr and adolescents. Thereafter, alkaline phosphatase activity declines, reaching normal adult levels after a growth spurt during adolescence...

Alkaline phosphatase increases markedly in diseases that impair bile formation (cholestasis) and to a lesser extent in hepatocellular disease...

Isolated elevations (ie, other liver tests are normal) occur in granulomatous hepatitis or focal liver disease (eg, abscess, neoplastic infiltration, partial bile duct obstruction)...

In some nonhepatic malignancies without liver metastasis, the mechanism is obscure. For example, bronchogenic carcinoma may produce its own alkaline phosphatase; hypernephroma in 15% of cases induces nonspecific hepatitis as the presumed origin of the enzyme elevation. For Hodgkin's lymphoma, the cause of the isolated alkaline phosphatase elevation is unknown. Generally, an isolated alkaline phosphatase elevation in an otherwise asymptomatic elderly adult is not worth investigating. Most cases originate from the bone (eg, in Paget's disease)."
 

Kalel

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I agree with the explanation written above. I just wanted to add that these days, some labs actually differentiate between isoenzymes of alkaline phosphatase released from your GI tract and liver, and the alk phos released from your bone. That can be useful in your work-up of a patient with an elevated alk phos. Alk phos can be lower in a patient with chronic myelogenous leukemia or with other conditions such as malnutrion, aplastic anemias, pernicious anemias, etc. In CML, the CML granulocytes lack the enzyme to produce alk phos, therefore when the CML begins to replace leukocytes that normally produce alk phos, the levels of alk phos decrease.
 
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alk phos is usually intracellular, so when extracell levels are elevated, it demonstrated a problem at the cellular level- eg, cirrhosis of the liver would cause ruptured parenchymal hepatocytes spillin' out the alk phos as well as other stuff.. your alt's, etc.

same goes for the bone i suppose.. i only knew abt the liver
 
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