Variable efficacy of bone remodeling biochemical markers in the management of patients with Paget's disease of bone treated with tiludronate.

The aim of this work was to evaluate the response of different biochemical bone markers to tiludronate administration in Paget's disease of bone. Ten patients (five men and five women), 56-77 years old (67 +/- 6.5), were treated for 3 months with tiludronate tablets (400 mg/day). Bone formation markers: alkaline phosphatase (AP), bone alkaline phosphatase (bAP), osteocalcin (BGP), and procollagen I carboxyterminal propeptide (PICP) in serum; and bone resorption markers: serum cross-linked carboxyterminal telopeptides of type I collagen (ICTP), urinary hydroxyproline/creatinine (Hyp/Cr), pyridinoline/Cr (Pyr/Cr), and alpha-1 collagen chain products degradation (CrossLaps) were assessed. Samples were taken before and at monthly intervals for 3 months after treatment began. The results of the present work show that serum AP and bAP are sensitive and reliable biochemical markers of bone formation in the follow-up of tiludronate in this disease. Serum PICP shows less sensitivity than serum AP, and serum BGP is not indicated as biochemical marker in these types of studies. Urinary hydroxyproline seems to be the most reliable biochemical marker of bone resorption. More studies should be performed with urinary Pyr and CrossLaps determinations. Serum ICTP is not adequate for the follow-up of tiludronate treatment in Paget's disease of bone.