Alkaline phosphatase is a hydrolase enzyme and in humans it can be found in the all tissues. Still the highest concentration of alkaline phosphatase is in the liver, bile duct, kidneys, bones and placenta. Humans contain several alkaline phosphatase isoenzymes including ALPI- intestinal, ALPL- tissue non-specific (located in the liver, kidneys and bones) and ALPP- placental.
This enzyme is involved in removal of phosphate groups from different molecules. The process of phosphate group removal is known as dephosphorylation. The enzyme functions best in alkaline environment (pH of around 8). Measuring the levels of alkaline phosphatase may be of great help and even the slightest changes may point to the presence of certain medical condition.
When is Alkaline Phosphatase Checked
A blood test to check for alkaline phosphatase levels is indicated in case there are symptoms and signs of systemic disorders. This particularly refers to disorders related to abnormal liver functioning. In some cases alkaline phosphatase can be checked routinely.
Interpreting ResultsNormal Alkaline Phosphatase LevelsPrior interpretation of the results the doctor has to take into consideration certain factors. Namely, some medications may interfere in results and this is why patients are advised to stop taking specific medications for a while prior blood testing. This is crucial and by doing so the result will be more valid. Such medications include allopurinol, antibiotics, cortisone, propranolol, birth control pills and so on.
Normal levels of alkaline phosphatase vary between 30 and 140 IU/L. This test solely cannot be used in setting of the diagnosis but it is very helpful and together with symptoms and signs of the disease and additional tests and examination it helps a lot in setting of the definitive diagnosis.High Alkaline Phosphatase LevelsThere are many factors and illnesses which contribute to the occurrence of high levels of alkaline phosphatase. Firstly, elevated levels of alkaline phosphatase point to problems related to normal functioning of the liver. Alkaline phosphatase is elevated in cholecystitis, cholangitis, fatty liver disease, hepatitis and many more liver disorders and illnesses. High levels of alkaline phosphatase are also characteristic for bone disorders. They include Paget's disease, renal osteodystrophy, bone fractures, hyperparathyroidism, osteomalacia, riskets etc. Apart from the previously mentioned elevation of alkaline phosphatase may also affect pregnant women, patients suffering from myelofibrosis, polycytemia vera, seminoma etc.Low Alkaline LevelsLow alkaline phosphatase levels do not occur so often. Still, their presence may point to hypophosphatasia, hypothyroidism, malnutrition, pernicious anemia, aplastic anemia, enteritis and so on. Low level of this enzyme is typical for children suffering from certain congenital diseases (cretenism and achondroplasia). And finally, low levels of alkaline phosphatase are a characteristic of osteoporosis in post menopausal women.