Alkaline phosphatase is an enzyme present in various tissues of the body. It is found mostly in the bones and in the liver, although it can also be found in the kidneys, the placenta of pregnant women, and the intestine. In blood work, it can be useful test to measure damage to these tissues, as well as tracking improvement with appropriate therapy.
Facts about Alkaline Phosphatase
The alkaline phosphatase in the liver is found within the bile ducts, the tubes that drain bile from the liver into the intestine to help in the digestion of fats. Osteoblasts, the cells in charge of bone formation, secrete alkaline phosphatase within bones. Although its function within bone is not well understood, elevation of alkaline phosphatase indicates high bone turnover. Likewise, elevation of the alkaline phosphatase level on blood tests can indicate liver, bone and bile duct damage.
Test Sample
Each tissue has a specific type of alkaline phosphatase, the isoenzymes. By breaking down the test into the different isoenzymes, it is possible to pinpoint the actual organ involved. A low alkaline phosphatase can be present after blood transfusions, heart bypass surgery, and if the person has a zinc deficiency. Children and adolescents have a higher than normal baseline alkaline phosphatase level. This is a result of rapid bone turnover that is associated with growth spurts.
Causes of Changes in the Alkaline Phosphatase Level
There are several causes of elevation of the alkaline phosphatase test. Drugs such as certain antibiotics, birth control pills and anti-inflammatory medication can cause an elevation of this enzyme. Other causes include conditions that cause excessive bone formation, like Paget's disease, a cause of bone weakening due to rapid formation and destruction of bone; and conditions that cause blockage of the bile ducts, like gallstones. Other conditions that cause elevation of the alkaline phosphatase level include alcoholic liver disease, liver and bone cancers and leukemia.
Symptoms of Elevation of Alkaline Phosphatase
The symptoms that accompany alkaline phosphatase elevation depend on the underlying condition. Paget's disease of the bone presents with bone pain, weakness and deformity of bones, fracture, and joint pain and swelling. Gallstones can cause pain in the right upper section of the abdomen, dark urine, fever and itching. Alcoholic liver disease and liver malignancies can also cause right-sided abdominal pain, weight loss, and jaundice, a yellowish discoloration of the skin.
