Glucocorticoid-induced osteoporosis
1. How common is glucocorticoid-induced osteoporosis (GIOP)?
Glucocorticoid-induced osteoporosis (GIOP) is the most common cause of secondary osteoporosis. Significant bone loss and skeletal fractures may occur within 6 months of starting glucocorticoid therapy, and up to 50% of people undergoing long-term glucocorticoid treatment have osteoporotic fractures.
2. What are the important determinants of bone loss with glucocorticoid therapy?
Bone loss is related mainly to the dose and the duration of glucocorticoid therapy. Prednisone doses of 7.5 mg or higher (or equivalent doses of other glucocorticoids) are associated with the greatest risk. However, a large cohort study showed a significantly increased fracture risk even in those whose median prednisolone doses had been as low as 2.5 mg daily. Decreased bone mass and increased fracture risk have also been demonstrated with inhaled glucocorticoids.
3. Explain the pathogenesis of GIOP.
Glucocorticoids adversely affect three phases of bone remodeling. Bone formation is impaired by apoptosis (cell death) of existing osteoblasts and decreased recruitment of new osteoblasts. Glucocorticoids also promote apoptosis of osteocytes, the mechanoreceptors that normally maintain bone strength by coordinating bone remodeling so that older, weaker bone is continuously replaced by newer, stronger bone. Finally, bone resorption is initially increased through various mechanisms, including decreased production of sex steroids and osteoprotegerin, an endogenous inhibitor of bone resorption (Fig. 9-1).
4. What are the BMD criteria for a diagnosis of GIOP?
The ideal bone mineral density (BMD) criteria for the diagnosis of GIOP are still being debated, but the best existing evidence suggests that the fracture risk per BMD decrement is higher in GIOP than in primary osteoporosis. The same BMD criteria are currently used to diagnose osteoporosis in patients taking glucocorticoids as in those who are not taking glucocorticoids, but active treatment should be considered at an earlier stage (T-score ≤ −1.0) because of the rapidity of bone loss in GIOP.
5. In which patients taking glucocorticoids should BMD be tested?
Patients who are starting glucocorticoid therapy (prednisone dose ≥ 5-7.5 mg/day or equivalent) with planned treatment duration of 3 months or longer or who have been receiving treatment for 3 months or longer.
