Is deoxypyridinoline a good resorption marker to detect osteopenia in phenylketonuria?

Objectives: To evaluate deoxypyridinoline as a resorption marker in phenylketonuria (PKU) and to search for a relationship between deoxypyridinoline, calcium/creatinine index (Ca/Cr I), osteocalcin and bone alkaline phosphatase (BAP). Methods: This was a transversal analytical study of 46 PKU patients [17.5 (4–38) years]. Deoxypyridinoline and osteocalcin were measured with a chemiluminescent assay and BAP was measured with an immunoradiometric assay. Results: Deoxypyridinoline was significantly increased in patients aged 7–14 and >18 years old, being associated with age (r = −0.724, P < 0.001). Adult patients showed significantly higher Ca/Cr I, which correlates with Phe values for the year prior to the study (P = 0.014). Serum BAP was significantly increased in pediatric patients (9–13 years), while it was decreased in adult patients (P = 0.003). Decreased osteocalcin levels were found in patients >15 years (P = 0.028). Altered deoxypyridinoline and BAP values were related (P = 0.042). Conclusion: PKU patients excreted increased D-Pyr, suggesting high bone resorption. Bone formation seems active in childhood but deteriorates in adult PKU patients. Periodic measurement of D-Pyr and BAP may be useful in the prevention of osteopenia in PKU patients.