Osteoporosis, bone mineral density and CKD-MBD: treatment considerations

Osteoporosis and chronic kidney disease (CKD) have both independently important potential impact on bone health. A significant number of patients with CKD stages 3a-5D have been shown to have low bone mineral density (BMD), leading to a strikingly elevated risk of fractures (mainly hip fractures) and higher associated morbidity and mortality. Mechanical properties of bone beyond age and menopausal status are additionally affected by intrinsic uremic factors. Therefore, we review in this article not only general concepts of osteoporosis and related consequences, but also the diagnostic and therapeutic implications of low BMD and bone fractures in CKD, beyond increased vascular calcification. Antiresorptive agents (mainly bisphosphonates) were not previously recommended when the estimated glomerular filtration rate (GFR) was lower than 30 ml/min/1.73 m². However, post-hoc analysis of large randomized clinical trials found that these drugs (i.e. alendronate, ribandronate, denosumab) had comparable efficacy in improving BMD and reducing fracture risk in individuals (mainly women) with moderate reductions of GFR (mostly CKD stages 3-4). Therefore, at least in the absence of clear abnormalities of CKD-related mineral metabolism disturbances, bone antiresorptive agents (and maybe anabolic agents) that are or will be approved for general osteoporosis may be appropriate for CKD. Nephrologists should probably not ignore any longer fracture risk assessment, especially in patients with additional risk factors for osteoporosis if results will impact treatment decisions. However, although different therapeutic agents have been shown to reduce the risk of fracture in CKD patients with low BMD, specific prospective studies, with or without bone biopsies, in CKD are urgently needed.