Endocrine Abstracts

During the last years, bone turnover markers (BTMs) have gained importance as surrogate markers to monitor both anti-resorptive and anabolic treatment, and may be used in conjunction with bone mineral density (BMD) measurements in clinical practice. The two most widely utilized BTMs are pro-collagen type 1 N-terminal propeptide (PINP), which reflects osteoblast activity, and C-terminal-cross-linking telopeptide of type 1 collagen (CTX), which corresponds to the osteoclastic function. BTMs can be measured on several occasions in one individual with good precision. However, these markers are subject to several sources of variability; including feeding (resorption decreases) and recent fracture (all markers increase for several months). BTMs are not used for diagnosis of osteoporosis and do not improve prediction of bone loss or fracture within an individual. In people with osteoporosis, BTMs might be useful to evaluate the response to anabolic and antiresorptive therapies, to assess compliance to therapy, or to indicate possible secondary osteoporosis. While prior treatment with bisphosphonates results in smaller BMD and BTMs changes in patients transitioning to denosumab as compared to treatment-naïve patients beginning denosumab therapy, it has also been proposed to blunt enhanced bone turnover and/or attenuate BMD loss after denosumab discontinuation. On the contrary, postmenopausal women switching from teriparatide (TPTD) to denosumab depicted a continued increase in BMD, with bone resorption maximally suppressed after 1-month of denosumab and a delayed suppression of bone formation with maximal effects after 12–24 months of denosumab treatment. More studies are needed to investigate the use of bone turnover markers for assessment of the bone safety of new medications.