Alkaline phosphatase in clinical practice in childhood: Focus on rickets

Abstract

Serum alkaline phosphatase (ALP) and its isoenzymes reflect bone metabolism: ALP increases the ratio of inorganic phosphate to pyrophosphate systemically and facilitates mineralization as well as reduces extracellular pyrophosphate concentration, an inhibitor of mineral formation. On the contrary, low ALP activity is associated with reduction of bone turnover. ALP includes four isoenzymes depending on the site of tissue expression: intestinal ALP, placental ALP, germ cell ALP and tissue nonspecific ALP or liver/bone/kidney ALP. The bone isoenzyme (B-ALP) is involved in bone calcification and is a marker of bone turnover as a result of osteoblastic activity. ALP and its isoenzymes are crucial in the diagnostic process of all the forms of rickets.The most common cause of rickets is vitamin D nutritional deficiency. The aim of this review is to update on the role played by ALP serum concentrations as a relevant marker in thediagnosis and treatment of rickets. Indeed, the diagnosis of rickets is based on its clinical, radiological and laboratory characteristics. An elevated ALP level is one of the markers for the diagnosis of rickets in children, though it is also associated with bone formation process. ALP is also useful for the differentiation between rickets and other disorders that can mimic rickets because of their clinical and laboratory characteristics, and, together with other biochemical markers, is crucial for the differential diagnosis of the different forms of rickets. Age, severity and duration of rickets may also modulate ALP elevation. Finally, ALP measurements are useful in clinical and therapeutic follow-up.

Calcium, Phosphorus, and Vitamin D Levels in a Series of Cystic Fibrosis Patients: A Cross-Sectional Study

“…Two were homozygous women (23 and 25 years) and another was a heterozygous woman (20 years). In general, ALP is 1.5-2.5 times higher in children than in adults [122]. While PA activity in women is highest between 10 and 12 years (ALP of 240 and 400 IU/L), male activity peaks between 13 and 15 years (ALP of 250 and 450 IU/L) [123].…”

“…ALP reflects the growth rate in height [125]. Although ALP is elevated due to rickets, it may also be increased in HPT, leukemia, Hodgkin's lymphoma, congestive heart failure, ulcerative colitis, viral hepatitis, Paget's disease, fibrous dysplasia, hepatobiliary disease, and during pregnancy [122]. In preterm infants, a serum ALP > 500 IU/L, observed in seven patients (41%) in our series, might indicate osteoporosis (100% sensitivity and 80.77% specificity), being recommended as a reliable biomarker to predict the development of poor bone mineralization [126].…”

Vitamin D Deficiency in Chronic Childhood Disorders: Importance of Screening and Prevention

“…PTH enhances bone resorption and activates 1-alpha hydroxylase in the kidneys to synthesise calcitriol [ 31 ]. It also decreases renal calcium excretion to maintain normocalcaemia [ 32 ].…”

“…High Alkaline Phosphatase (ALP) or Hyperphosphatasaemia High ALP, although not very specific, is an easily assessable marker of increased bone turn-over and should raise the suspicion of VDD if found to be raised in children [24,32]. It may be less helpful in conditions affecting the liver unless bone-and liver-specific isoenzymes are measured.…”

A GMR enzymatic assay for quantifying nuclease and peptidase activity

“…Monitoring enzymes is essential to understand cellular processes and disease mechanisms, and many enzyme-based disease biomarkers have been identified. For example, serum amylase and serum lipase assays are used to diagnose acute pancreatitis ( Walkowska et al, 2022 ), alkaline phosphatase activity in blood is a marker for liver or bone conditions ( Cannalire et al, 2023 ), creatine kinase tests diagnose Duchenne’s Muscle Dystrophy in neonates ( de Freitas Nakata et al, 2021 ), and elevated lactate dehydrogenase in blood is associated with poor prognosis in COVID-19 patients, potentially for use as a triage mechanism ( Martha et al, 2022 ). Among enzymes, hydrolases are crucial in regulating intracellular pathways and, as a result, influence diverse physiological and pathological conditions.…”