Pathophysiology of glucocorticoid-induced osteoporosis

Osteoporosis is the most deleterious effect of glucocorticoid therapy and occurs in up to 50% of patients receiving long-term therapy. Although the exact mechanism for this effect is unclear, various direct and indirect effects on bone remodeling are apparent. Bone remodeling is a continual and controlled cycle of bone resorption followed by bone formation. Glucocorticoids interrupt this balanced process through effects on bone resorption, osteoblast function, calcium homeostasis, sex steroid levels, growth factors, prostaglandins, and cytokines. In addition, glucocorticoids induce muscle weakness and myopathy, which may worsen bone loss. Histomorphometric studies show an overall decreased mean wall thickness of bone and decreased total bone volume in patients receiving glucocorticoid therapy. The pathophysiology of glucocorticoid-induced osteoporosis is reviewed.