From the Guidelines
Alkaline phosphatase is a crucial enzyme found in various body parts, including the liver, bones, intestines, and placenta, playing a significant role in bone mineralization and bile production. According to a recent review article published in 2024 in the Alimentary Pharmacology and Therapeutics journal 1, elevated serum alkaline phosphatase (ALP) is common in patients with malignancy, often resulting from bone metastases, unrecognized tumor infiltration of the liver, or malignant biliary obstruction. The study highlights that ALP measurements are not generally used as an exclusion criterion for clinical trials, provided other liver tests meet the requirements.
Some key points to consider about alkaline phosphatase include:
- It is an enzyme that helps remove phosphate groups from various molecules
- It is essential for bone mineralization and bile production
- Elevated levels may indicate liver disease, bone disorders, or other conditions
- Normal levels vary by age, with children and adolescents naturally having higher levels due to bone growth
- The test is typically part of a comprehensive metabolic panel and requires no special preparation
In clinical settings, alkaline phosphatase is commonly measured in blood tests as a biomarker for liver and bone disorders, as noted in the study 1. Understanding alkaline phosphatase levels is vital for healthcare providers to diagnose conditions affecting the liver and bones, though abnormal results usually require additional testing to determine the specific cause.
From the Research
Definition and Overview of Alkaline Phosphatase
- Alkaline phosphatase (ALP) is an evolutionary conserved enzyme and widely used biomarker in clinical practice 2.
- It is a membrane-bound glycoprotein that catalyzes the hydrolysis of phosphate monoesters at basic pH values 3.
- ALP is divided into four isozymes depending upon the site of tissue expression: Intestinal ALP, Placental ALP, Germ cell ALP, and tissue nonspecific alkaline phosphatase or liver/bone/kidney (L/B/K) ALP 3.
Functions and Roles of Alkaline Phosphatase
- The bone isoenzyme of ALP may be involved in mammalian bone calcification, and the intestinal isoenzyme is thought to play a role in the transport of phosphate into epithelial cells of the intestine 3.
- Bone-specific alkaline phosphatase (B-ALP) is an isoform of ALP found in bone tissue and can predict fractures and heterotopic ossification 4.
- ALP is essential for biomineralization, and recent findings demonstrate a crucial role for BALP in the pathogenesis of vascular calcification and identified it as a promising predictor of mortality in CKD 5.
Clinical Significance and Applications of Alkaline Phosphatase
- Elevated activity of ALP in the circulation is universally recognized as a marker for skeletal or hepatobiliary disease 6.
- Serum ALP is measured as an indicator of bone or liver disease, and B-ALP is used as a bone turnover marker after spinal cord injury 4.
- BALP has been suggested as a biomarker of bone turnover in CKD-MBD, and its determination may have clinical benefits in CKD 5.