From the Guidelines
Elevated alkaline phosphatase (ALP) in children is often normal and related to bone growth, but persistent significant elevations warrant investigation to rule out underlying conditions such as vitamin D deficiency, liver disorders, or bone diseases. Children naturally have higher ALP levels than adults because their bones are actively growing, with levels typically 1.5-2.5 times adult values, as noted in the study by 1. This elevation is particularly pronounced during growth spurts in infancy and adolescence. However, if a child has elevated ALP, the pediatrician will typically assess for symptoms, examine growth patterns, and may order additional tests including liver function tests, vitamin D levels, and possibly imaging studies, as recommended by 1. Some key points to consider in the evaluation of elevated ALP in children include:
- The child's age and growth stage, as ALP levels naturally fluctuate during growth and development 1
- The presence of any symptoms such as bone pain, fractures, or signs of liver disease, which may indicate an underlying condition requiring treatment 1
- The results of additional tests, such as liver function tests, vitamin D levels, and imaging studies, which can help identify the cause of elevated ALP 1
- The potential for ALP elevation to be related to bone growth and development, rather than an underlying disease process, as noted in the study by 1 Treatment depends entirely on the underlying cause - vitamin D supplementation for deficiency, addressing liver disease if present, or specific treatments for bone disorders, as recommended by 1 and 1. Most isolated ALP elevations in otherwise healthy, growing children require no intervention beyond monitoring, as stated in the study by 1. Parents should avoid supplementing without medical guidance, as the elevation often represents normal physiological processes rather than disease.
From the Research
Causes of Elevated Alkaline Phosphatase in Kids
- Elevated alkaline phosphatase (AP) levels in children can be caused by various factors, including underlying hepatobiliary or bone diseases 2.
- However, in a significant proportion of cases, elevated AP is benign and requires no intervention, known as transient hyperphosphatasemia (THP) of infants and children 2.
Diagnosis and Treatment
- A diagnostic workup for elevated AP levels can be costly, and an algorithm can be used to determine when a "wait and see" approach is optimal 2.
- In some cases, elevated AP levels can be caused by hypovitaminosis D, but serum measurements of calcium, phosphate, and alkaline phosphatase are unreliable for diagnosing this condition, even in the presence of secondary hyperparathyroidism 3.
- Clinical suspicion based on history and awareness of risk factors should remain the gold standard for requesting serum vitamin D measurements 3.
Role of Alkaline Phosphatase in Bone Mineralization
- Alkaline phosphatase (ALP) plays a critical function in the formation of hard tissue and is highly expressed in cells of mineralized tissue 4.
- ALP increases inorganic phosphate local rates and facilitates mineralization, as well as reduces the extracellular pyrophosphate concentration, an inhibitor of mineral formation 4.
- The tissue-nonspecific isozyme of ALP (TNAP) is strongly expressed in bone, liver, and kidney and plays a key function in the calcification of bones 4.