We thank Dr. Fu Sang et al. for their comments on our article on the control of Paget’s disease of bone with low dose weekly oral bisphosphonates [1].

Regarding the use of total alkaline phosphatase (ALP) as disease activity marker, we acknowledge that P1NP may be somewhat better correlated with disease activity, however, P1NP was not available in our system during the time of the study, and even according to the meta-analysis cited by Fu et al. notwithstanding its limitations, the difference between P1NP and ALP is small and probably not clinically significant in most patients, except those with concurrent hepato-biliary disease [2]. As our end-point was definite normalization of ALP, we believe that having used a different bone turnover marker and assessing PTH and 25(OH)D at the time of initiation of each treatment course (rather than checking them periodically, as we did) would not have changed our conclusions on the efficacy of low-dose oral bisphosphonates in the treatment of Paget’s disease of bone. Since bone density has not been checked regularly, we are not able to answer the question regarding the effect of bisphosphonates for Paget’s disease on bone mass.