Paget's disease of bone

The response to therapy is assessed using alkaline phosphatase as a marker of osteoblastic activity. Alternatively, bone alkaline phosphatase may be used where available. In patients with localised disease and normal alkaline phosphatase, serum procollagen 1 N-terminal peptide (P1NP) or serum C-terminal propeptide of type 1 collagen (CTX) may be useful measures of bone turnover. Markers are measured after 6 months of treatment, and subsequently every 6 to 12 months or until symptoms reappear or increase (although the correlation between alkaline phosphatase levels and clinical symptoms is not optimal).