ALP

Any condition that affects bone growth or causes increased activity of bone cells can affect ALP levels in the blood. An ALP test may be used, for example, to detect cancers that have spread to the bone or to help diagnose Paget's disease. This test may also sometimes be used to monitor treatment of Paget's disease or other bone conditions, such as vitamin D deficiency.

If ALP results are increased but it is not clear whether this is due to liver or bone disease, then tests for ALP isoenzyme tests may be done to determine the cause. A GGT test and/or a test for 5'-nucleotidase may also be done to differentiate between liver and bone disease. GGT and 5'-nucleotidase levels are increased in liver disease but not bone disorders.

Signs and symptoms of liver involvement may include:

• Weakness, fatigue
• Loss of appetite
• Nausea, vomiting
• Abdominal swelling and/or pain
• Jaundice
• Dark urine, light colored stool
• Itching (pruritis)

Some examples of the signs and symptoms suggesting a bone disorder include:

• Bone and/or joint pain
• Increased frequency of fractures
• Deformed bones

If it is not clear from signs and symptoms or from other routine tests whether the high ALP is due to liver or bone, then a test for ALP isoenzymes may be necessary to distinguish between bone and liver ALP.

ALP in Liver disease
ALP results are usually evaluated along with other tests for liver disease. In some forms of liver disease, such as hepatitis, ALP is usually much less elevated than AST and ALT. When the bile ducts are blocked (usually by gallstones, scars from previous gallstones or surgery, or by cancers), ALP and bilirubin may be increased much more than AST or ALT. It may also be increased in liver cancer.

ALP in Bone disease
In some bone diseases, such as Paget's disease, where bones become enlarged and deformed, or in certain cancers that spread to bone, ALP may be increased.

If a person is being successfully treated for Paget's disease, then ALP levels will decrease or return to normal over time. If someone with bone or liver cancer responds to treatment, ALP levels should decrease.

Low levels of ALP may be seen temporarily after blood transfusions or heart bypass surgery. A deficiency in zinc may cause decreased levels. A rare genetic disorder of bone metabolism called hypophosphatasia can cause severe, protracted low levels of ALP.

Children and adolescents normally have higher ALP levels than adults because their bones are growing, and ALP is often very high during a growth spurt, which occurs at different ages in boys and girls.

Some drugs may affect ALP levels. For example, oral contraceptives may decrease levels while anti-epileptics may increase levels.