Usefulness of osteoprotegerin in assessing responses to neridronate treatment in Paget's disease of bone

Osteoprotegerin (OPG) is a protein that inhibits of osteoclastogenesis. The aim this study was to evaluate the response of serum OPG levels to neridronate treatment in patients with Paget's disease of bone resistant to previous therapy. Nine patients (4 men) affected by active Paget’s disease of bone (6 polyostotic, 3 monostotic) not responsive to clodronate were studied. Serum OPG, osteocalcin, total and bone isoenzyme of alkaline phosphatase (AP and BAP, respectively), and urinary deoxypyridinoline (DPD) were measured before and 5 months after neridronate treatment (100 mg/day, i.v. for two days). A scintigraphic activity index (SAI) was also calculated before treatment. Mean baseline OPG levels were within normal values and were not significantly different 5 months after neridronate treatment. In contrast, there were significant reductions in AP (41.9%, p