Medical treatment of severe osteoporosis including new concept of advanced severe osteoporosis

Osteoporosis is a metabolic bone disease characterized by decreased bone strength, leading to an increased risk of fracture. The World Health Organization (WHO) defines osteoporosis as a bone mineral density (BMD) of 2.5 standard deviations below that of a young adults (T-score of −2.5 or lower). Severe osteoporosis is differentiated from osteoporosis by the presence of one or more fragility fractures in addition to this T-score. However, the current WHO definition may be insufficient to reflect the diverse spectrum of osteoporosis or severe osteoporosis, which can encompass various number and severity of prevalent fractures. To overcome these shortcomings of the WHO definition of osteoporosis, we propose a concept of ‘advanced severe osteoporosis’, which is defined by the presence of proximal femur fragility fracture or two or more fragility fractures in addition to BMD T-score of −2.5 or less. Based on the previous clinical trials and post-hoc analyses, we recommend selective estrogen receptor modulators, bisphosphonates, receptor activator of nuclear factor kappa-B ligand (RANKL) monoclonal antibody, and parathyroid hormone for the medical treatment of severe osteoporosis. In cases of advanced severe osteoporosis or osteoporosis that does not respond to previous anti-osteoporotic treatments, we also recommend parathyroid hormone, bisphosphonates, and RANKL monoclonal antibody. In conclusion, we need more precise assessment of osteoporosis and further stratification of the disease by number of prevalent fractures in addition to BMD. More aggressive managements should be provided for those with advanced severe osteoporosis.