Alkaline phosphatase (ALP) is an enzyme found in several organs of the body, such as the liver, bones, placenta (during the third trimester), intestines, and kidneys. It plays a role in various physiological processes such as bone metabolism, bile secretion, and cell signaling.
This article explores the significance of the alkaline phosphatase enzyme in blood tests, including its interpretation, normal range, and factors that can cause high or low blood levels.
ALP in Blood Tests
ALP levels in the blood can be measured through a basic blood test. Elevated levels of ALP can indicate damage or injury to any organs that produce ALP. ALP is a non-specific enzyme, which means it can be elevated in various conditions, including liver and bone diseases. ALP tests may not always provide a definitive diagnosis when used alone.
Normal ALP Levels in a Blood Test
The normal range of ALP (alkaline phosphatase) levels can vary slightly among individuals due to factors such as age, gender, and ethnicity. ALP levels are typically higher in children and adolescents due to osteoblastic activity, which is a physiological process involved in bone formation. ALP levels in these age groups can be up to three times higher than in healthy adults.
Additionally, the serum alkaline phosphatase level typically increases gradually from age 40 to 65, especially in women. The normal ALP level for a healthy 65-year-old woman is over 50% higher than that of a healthy 30-year-old woman.
Causes of Increased Alkaline Phosphatase (ALP)
Alkaline phosphatase (ALP) is a non-specific enzyme that can be elevated in various conditions, including liver and bone diseases. An elevated ALP level in a blood test can indicate conditions related to liver-biliary system obstruction or bone diseases. A significant and severe increase in ALP (more than four times the normal limit) indicates cholestatic liver disease, while a mild to moderate increase can be caused by factors related to the liver or other factors.
Causes of a sharp increase in ALP
| Causes of a Sharp Increase in ALP | |
|---|---|
| Hepatobiliary Causes | |
| Obstruction of extrahepatic bile ducts | Gallstones (most common cause) |
| Malignancies causing obstructions in: | Ampulla of Vater |
| Gallbladder | |
| Pancreas | |
| Bile ducts | |
| Bile duct strictures: | Primary sclerosing cholangitis |
| Anatomical disorders of the bile ducts | |
| Infections: | AIDS cholangiopathy |
| Ascaris worms | |
| Liver flukes | |
| Obstruction of intrahepatic bile ducts | |
| Medications and toxins | |
| Primary biliary cholangitis | |
| Primary sclerosing cholangitis | |
| Intrahepatic cholestasis of pregnancy | |
| Intravenous nutrition (TPN) | |
| Liver metastases from cancers | |
| Ischemic cholangiopathy | |
| Sickle cell disease | |
| Non-hepatobiliary Causes | |
| Increased bone remodeling: | |
| Growth period | |
| Bone healing after fractures | |
| Osteomalacia | |
| Paget’s disease of bone | |
| Hyperthyroidism | |
| Hyperparathyroidism | |
| Bone sarcoma | |
| Bone metastasis | |
| Causes of Moderate Elevation of ALP | |
| Physiological factors (in children and adolescents) | |
| Third trimester of pregnancy | |
| Extrahepatic diseases: | |
| Peritonitis | |
| Diabetes mellitus | |
| Subacute thyroiditis | |
| Ulcers | |
| Extrahepatic tumors: | |
| Lung | |
| Stomach | |
Causes of low alkaline phosphatase (ALP) levels in the blood
Low levels of alkaline phosphatase are usually not clinically significant. It is recommended to assess the patient for deficiencies in zinc and magnesium, malnutrition, and hypothyroidism. An increase in ALP levels is clinically relevant and may indicate various diseases, necessitating further examination by a doctor.
Interpretation of the test results
Interpreting the alkaline phosphatase test requires considering the reasons for its increase or decrease, as well as the clinical symptoms of the disease and other relevant tests, especially liver function tests like ALT and AST. The doctor may recommend further investigations, such as a liver and gallbladder ultrasound, for a comprehensive evaluation.
It is important to note that elevated ALP levels for your age and gender do not always indicate a disease. Children and teenagers naturally have higher levels of ALP (alkaline phosphatase) due to ongoing bone growth.
If your ALP level is high, your doctor may order additional tests, such as ALT and GGT, to determine if the increased alkaline phosphatase is coming from the liver.
Low ALP levels may indicate zinc and magnesium deficiency, as well as a rare genetic condition called hypophosphatasia, which affects bones and teeth.
What is the normal value of ALP (alkaline phosphatase) in blood test?
The normal value of ALP varies in different ages and should be interpreted by a doctor, but in general its normal values are usually between 44 and 147.
What is the sign of low alkaline phosphatase?
A low level of ALP can indicate a deficiency of magnesium, zinc, malnutrition, or a rare disease called hypophosphatasia.
What are the ways to reduce alkaline phosphatase?
The way to reduce ALP is to find and treat its underlying cause. So, first the cause of its increase should be determined and then the cause should be removed. In most cases, gallstones can cause an increase in ALP, the treatment of which is surgery and removal of the gallbladder.
Is high alkaline phosphatase (ALP) dangerous?
Yes, it can be dangerous and should be checked by a doctor immediately
