Calcium and vitamin D therapy in corticosteroid-induced bone loss: what is the evidence?

Corticosteroid-induced osteoporosis (CIO) is a serious disorder that results in significant long-term morbidity. Increased bone resorption is caused by decreased Ca absorption and increased urinary Ca excretion leading to secondary hyperparathyroidsim. Calcium prophylaxis alone, when patients start corticosteroids, is associated with rapid rates of spinal bone loss and offers only partial protection from corticosteroid-induced spinal bone loss. Though calcium supplementation may have some benefit, it clearly cannot completely prevent corticosteroid-induced bone loss. At most, Ca therapy should only be considered adjunctive therapy in the treatment or prevention of corticosteroid-induced bone loss and should be administered in combination with other treatments. Earlier work demonstrated increases in forearm bone mineral density (BMD) with the use of Ca and vitamin D in patients with established CIO. However, caution should be taken when interpreting these results, since bone loss generally tapers or plateaus after the first 12 months of corticosteroid treatment; as such, any therapy might show benefit. In addition, bone density was only taken at the radius and not the spine where most of the bone loss takes place. Nonetheless, in recent trials of at least 2-year duration in which calcium and vitamin D therapy served as placebos, the result indicated that bone mass was maintained at the spine and hip throughout treatment in patients who had used chronic corticosteroids. In primary prevention trials, the amount of bone loss observed in the spine after therapy with Ca and vitamin D combinations is similar to that observed in other prevention studies in the Ca alone-treated control groups. Furthermore, Ca and vitamin D therapy appears to be less effective than other agents in the prevention of corticosteroid-induce bone loss. Although several studies do not report side effects that may be associated with Ca and vitamin D therapy, the few that do frequently report hypercalciuria. In the absence of other studies that support the use of Ca and vitamin D in the prevention of CIO, the data are too limited to generally recommend them alone as a preventative therapy. Activated vitamin D may be of greater benefit.