A test for levels of alkaline phosphatase, or ALP, in your blood is performed when your health care provider wants to assess the health of your liver or bone growth. ALP is an enzyme produced by all tissues in the body, but is particularly high in the liver, bile ducts and growing bone. A high level of ALP is common in children and pregnant mothers, but in the general adult population, it indicates liver damage or a condition inducing abnormal bone growth.
About Alkaline Phosphatase
Phosphatases are enzymes that remove phosphate groups from proteins, other enzymes and molecules. The purpose of phosphatase activity varies widely between phosphate metabolism, biological signaling, enzyme regulation and DNA processing. Alkaline phosphatase functions best in alkaline tissues of the body, as in the liver and bones. The precise reason why ALP is elevated in certain conditions is not fully known.
Liver Disease
ALP levels in the blood can be high if you have liver damage or disease. Your health care provider will likely perform other tests of liver function to determine whether elevated ALP indicates liver disease. If these further liver tests are inconclusive, a test can be performed to determine whether elevated ALP is from liver or bone cells. In testing, liver ALP will not be broken down by heat whereas ALP from bone cells will.
Bone Growth
ALP levels in the blood can be raised due to high production in osteoblasts, cells that produce new bone. ALP levels are elevated during pregnancy or childhood due to normal bone growth or during repair following a fracture. Elevated ALP in adults that is not associated with liver disease indicates a condition that induces inappropriate bone growth. Conditions that cause this include Paget's disease, in which bone become enlarged and deformed.
Other Factors
Use of alcohol or drugs can cause an increase of ALP levels even in the absence of disease. Other medications can artificially elevate ALP and you may be instructed by your health care provider to temporarily stop taking these prior to an ALP test. These drugs include antibiotics, anti-inflammatory drugs, antidepressants, anticonvulsants and hormones used for hormone replacement or birth control.
