Although zoledronic acid and denosumab are currently regarded as the most potent antiresorptive agents, there is no head-to-head comparative study. This study primarily aims to the comparative effect of zoledronic acid and denosumab on serum sclerostin levels and secondarily on serum dickkopf-1, osteoprotegerin, RANKL and bone turnover markers (procollagen type I N-terminal peptide [PINP] and C-terminal cross-linking telopeptide of type I collagen [CTX]).