[Glucocorticoids and osteoporosis]

Abstract

Treatment with glucocorticoids (GC) has no alternative in many medical disciplines for their anti-inflammatory and immunosuppressive effect. However, osteoporosis and the related fractures are a serious complication brought about by long-term GC therapy. The risk of fractures, especially of the vertebras and the ribs, becomes higher as early as in the first months of oral GC therapy. It grows in proportion to the daily dose of GC, and is present even if low doses are administered (2.5-7.5 mg of prednisone per day). Decreasing bone density (BMD) is not accountable for the higher risk of fractures in GC therapy and fractures occur with higher values of BMD than in primary osteoporosis. There is still no tool that we could use to quantify the changes in the bone quality and the increased risk of fracture in clinical practice. The principal mechanism by which GC induces osteoporosis is inhibition of bone formation caused by the suppression of osteoblastogenesis as well as the activity of functional osteoblasts, with accelerated osteocyte and osteoblast apoptosis. There are significant differences between individuals in terms of GC sensitivity, the reasons of which have not yet been explained. Prior to planned long-term GC therapy (> 3 months) with daily doses higher than 2.5 mg of prednisone p.o. (or higher doses of inhaled GC), it is recommended to perform a densitometry exam using dual-energy X-ray absorptiometry (DXA) in the lumbar region of the spine and femoral collum to evaluate additional risk factors of osteoporosis and fractures for a more precise estimate of the risk of fracture in the specific patient. Sufficient intake of calcium (1,000-1,500 mg of elementary calcium per day) and of the vitamin D (800 IU per day) should be assured in all patients treated by GC. Endogenous production of sexagens should be evaluated and possible substitution therapy should be considered in premenopausal women and younger men. Today, bisphosphonates can be given to patients with a high risk of fracture, the effects of which in preventing the decrease of BMD and vertebral fractures have been documented in randomised clinical studies, even though the evaluation of the risk of fractures was not the primary endpoint of those studies. However, in view of the antiremodelling effect of bisphosphonates, it is clear that this therapy does not eliminate the cause of GC induced osteoporosis and drugs with stimulating effect on osteoblasts will certainly be preferred in the future. Very promising are the first clinical studies of injection parathormone (PTH 1-34) which stimulated bone formation in a continuing GC treatment.