Alkaline phosphatase (abbreviated as ALP) is a group of hydrolase enzymes, present in the human body. There are several ALP isoenzymes, known as ALP1, ALP2 and ALP3. ALP1 is usually found in the liver, ALP2 in the human bone, placenta and kidneys, while ALP3 is mostly found in the lining of the intestines. These tissues all release ALP to the bloodstream. To work, this enzyme need alkaline pH (around 10), and in that surrounding it is able to take a phosphorus group of certain molecules. The process is known as de-phosphorylation and it is performed on alkaloids, proteins and nucleotides in the body.
The ALP blood tests are measuring the total amount of all ALP isoenzymes in the body. Usually, they are done to diagnose some bone and liver diseases, or to establish the toxic effects of medications to the liver. Another reason to perform ALP test is to detect some other medical conditions, including: malnutrition, protein deficiency, alcoholism, liver cirrhosis, gallstones, kidney carcinoma, endocrineoplasia (endocrine glands tumors), etc.
Normal ALP Levels
The level of ALP mainly depends on the age, but also on the activity and stage of growth of bone cells (osteoblasts and osteoclasts). As normal level of alkaline phosphatase, doctors consider the values between 50 and 75mg/dl (milligrams per deciliter). Teenagers and young adults might normally have slightly higher ALP levels than adults.
Everything over 75mg/dl is considered as high ALP level and it is not healthy, since it might indicate some bone, placental, intestinal or liver problems.
What Can Cause High ALP?
Many conditions and diseases could cause high level of alkaline phosphatase in the blood. As we already said, it is normal for adolescents, but also for some pregnant women, to have slightly increased level of blood ALP.
Bone diseases and cancers, especially Paget’s disease can cause high blood ALP and lead to bone deformities, pain and abnormal bone fractures. Liver cholestasis and congestion, obstruction of the biliary tracts, inflammation caused by medications or increased level of toxins in the liver might also cause elevated levels of ALP.
Other causes of high ALP include various conditions, such as: virus and parasitic infections, gastrointestinal of systemic infections, congestive heart failure myocardial and pulmonary infarctions, leukemia, sarcoidosis, amyloidosis, Hodgkin’s lymphoma, rheumatoid arthritis or obstructive pancreatitis, etc. Abnormal functioning of the glands in the human body might also provoke high level of alkaline phosphatase in the blood. Over activity of the thyroid or parathyroid glands, or adrenal cortical hyperfunction can be some of the reasons for high ALP. Different gynecologic malignancies or increased use of contraceptive tablets could also cause high level of alkaline phosphatase in the bloodstream.