HMG-CoA reductase inhibitors in osteoporosis: do they reduce the risk of fracture?

Osteoporosis affects a large number of people in industrialised countries. It has clinical and public-health impacts, most importantly due to subsequent fractures. Osteoporotic fractures are one of the most common causes of disability and are associated with enormous healthcare expenditure. The majority of existing treatment options for osteoporosis only inhibit bone resorption and prevent excessive bone loss but are not capable of stimulating bone formation. However, several recent in vitro and in vivo studies in animals demonstrated that HMG-CoA reductase inhibitors stimulate the production of bone morphogenetic protein (BMP-2), which is a potent regulating protein in osteoblast differentiation and activity. This suggests that HMG-CoA reductase inhibitors may have an anabolic effect on bones, making them a potentially interesting treatment option for osteoporosis. Additionally, several studies in humans showed that some HMG-CoA reductase inhibitors may have a beneficial effect on bone turnover and may lead to an increase in bone mineral density. Consequently, several observational studies tried to evaluate whether use of HMG-CoA reductase inhibitors is associated with a decreased risk of fractures. Even though not all results of these epidemiological studies, using different designs in different study populations, were entirely consistent, they provided substantial evidence that HMG-CoA reductase inhibitor use may decrease the bone fracture risk by approximately 50%. On the other hand, reanalysis of two randomised controlled trials of HMG-CoA reductase inhibitor therapy, designed to assess cardiovascular outcomes, could not show that patients treated with HMG-CoA reductase inhibitors had a lower fracture risk in comparison with placebo-treated patients. Therefore, to conclusively assess the potential of HMG-CoA reductase inhibitors in the prevention and treatment of osteoporosis, randomised controlled trials need to be performed to address this conflicting issue. Until the results of such trials are available, practitioners should prescribe the drugs that have been proven to reduce the risk of osteoporotic fractures.