From the Guidelines
Alkaline phosphatase (ALP) is indeed elevated in patients with rickets and osteomalacia, serving as a reliable biomarker of disease activity in both children and adults. This elevation is attributed to the increased osteoblastic activity in response to inadequate mineralization of bone due to vitamin D deficiency, calcium deficiency, or phosphate abnormalities 1. The body's attempt to compensate for the mineralization defect leads to higher ALP levels in the bloodstream.
Key points to consider in the context of ALP elevation in rickets and osteomalacia include:
- The degree of ALP elevation often correlates with disease severity, making it a useful marker for diagnosis and monitoring treatment response.
- In children, total ALP can be used as a reliable indicator because bone-specific ALP represents approximately 80-90% of total ALP in the serum 1.
- In adults, however, bone-specific ALP is preferred for monitoring because only about 50% of circulating ALP originates from bone, with the remainder coming from hepatocytes 1.
- As treatment progresses and the underlying deficiencies are corrected, ALP levels typically normalize, indicating improvement in bone mineralization and disease activity 1.
Monitoring ALP levels, along with other biochemical markers such as parathyroid hormone (PTH), serum and urinary calcium, and phosphate, is crucial for the effective management of rickets and osteomalacia 1. This comprehensive approach helps in assessing disease severity, guiding treatment, and evaluating the response to therapy, ultimately aiming to improve morbidity, mortality, and quality of life for patients with these conditions.
From the Research
Alkaline Phosphatase (ALP) Levels in Rickets and Osteomalacia
- ALP is a marker of bone turnover and is involved in bone calcification 2.
- Elevated ALP levels are associated with the diagnosis of rickets in children, and ALP measurements are useful in clinical and therapeutic follow-up 2.
- In hypophosphatemic rickets, ALP levels are elevated, and active vitamin D and phosphate are administered to correct hypophosphatemia and elevation of ALP 3.
- However, in hypophosphatasia, a rare disorder characterized by deficient activity of the tissue nonspecific isoenzyme of alkaline phosphatase, ALP activity is low, leading to rickets or osteomalacia despite normal or elevated circulating levels of calcium and inorganic phosphate 4.
- Bone alkaline phosphatase (BAP) and the BAP/PINP ratio are increased in oncogenic osteomalacia (OOM) but not in X-linked hypophosphatemic rickets (XLH) patients, suggesting a disturbance in bone mineralization in OOM 5.
Specific Conditions and ALP Levels
- In hereditary hypophosphatemic rickets, ALP levels are elevated, and treatment with active vitamin D and phosphate can help correct hypophosphatemia and elevation of ALP 3.
- In hypophosphatasia, low ALP activity is associated with rickets and osteomalacia, and matrix vesicles in osteomalacic hypophosphatasia bone contain apatite-like mineral crystals, suggesting a block in the vectorial spread of mineral from initial nuclei within matrix vesicles 6.
- In vitamin D deficiency rickets, ALP levels can be elevated, and treatment with cholecalciferol can help improve rickets and reduce ALP levels 4.