Measurement of alkaline phosphatase (ALP) in blood helps diagnose many diseases, especially bone and liver diseases. Causes of high blood ALP levels are described in this article. Read on to know ALP functions, and when the ALP levels are usually checked.
Alkaline Phosphatase (ALP) is an important enzyme which helps in body metabolism in various ways. Though it is present in all tissues, maximum amount of ALP is found in liver and bones. It is also present in bile duct, intestinal lining, placenta, kidneys, and various other parts of the body. 25-100 units per liter (U/L) is considered as a reasonable range of ALP in adults. Children might have slightly higher levels. It is a type of hydrolase enzyme. An alkaline environment promotes optimal functioning of this enzyme. An environment with pH of around eight is considered as the best environment for the efficient working of this enzyme.
Causes of High Blood ALP Levels
Doctors order a blood test to check ALP levels if they suspect bone, liver, intestinal, or placental disorders. Jaundice, abdominal pain, nausea, and vomiting are some common symptoms of liver diseases or damaged liver cells. Rapid bone growth during puberty contributes to high blood ALP in children and adolescents. Increased osteoblastic activity in bone diseases, and affected calcium levels in blood can lead to increased levels of ALP.
- Bone cancer
- Paget’s disease
- Osteomalacia and rickets (softening of bones)
- Bone fracture
- Bone metastases
- Renal osteodystrophy
- Increased activity of osteoclasts during bone growth
- Pregnancy, when the placenta also secretes ALP
- Some other types of cancers like cancer of testes (generally found in older men)
- Cholestasis, when little or no bile is secreted, or when bile flow is obstructed
- Viral hepatitis
- Poorly controlled diabetes
- Excessive use of antibiotics or other medicines like anti-epileptics, antidepressants, anti-inflammatory drugs
- Excessive use of birth control pills
- Alcohol abuse
- Smoking, excessive use of tobacco
- Heart attack
- Inflammatory bowel disease
- Serious infections like herpes zoster
- Rheumatoid arthritis
- Hyperthyroidism or parathyroid gland overactivity
- Myocardial or pulmonary infarctions
- Adrenal cortical hyperfunction
- Gastrointestinal inflammation
ALP is required by the body for ‘dephosphorylation’, the removal of phosphate groups from different molecules. Like many other enzymes, ALP is a glycoprotein which helps remove phosphate from alkaloids, nucleotides, and proteins. It is required for the synthesis of proteins within cells, and plays an important role in the calcification of cartilage and bones. It promotes bone resorption by removing a layer of phosphate that is present on the surface of the bones. It is required for the synthesis of DNA, as it hydrolyzes both DNA and RNA.
A blood test to measure ALP levels is performed, when suggested by the doctor. It helps diagnose various diseases. It also helps assess liver function. Doctors need to perform the test to judge the effect of long term use of prescription drugs on liver, so that they can determine correct dosage levels, and avoid health complications. It has been noticed that Mg2+, Co2+, Mn2+, and amino alcohols trigger the reactions which utilize ALP.
As seen above, a number of factors are responsible for elevated ALP. When the levels are slightly high, the doctor may not be able to find the exact reason behind the disorder. It has been observed that in most of the cases, the levels return to their normal on their own after some months. Statistics show that if the increase in the level of alkaline phosphatase is greater than 1.5 times the normal value, then the reason behind the elevation is more likely to be liver or bone disease. Very low ALP indicates a genetic disorder known as ‘hypophosphatasia’ which results in bone deformities, or can even prove to be fatal, if neglected.
Disclaimer: This HealthHearty article is for informative purposes only, and should not be used as a replacement for expert medical advice.