Glucocorticoid-induced cortical bone porosity in postmenopausal patients with asthma

In a previous study, we demonstrated that chronic administration of systemic glucocorticoids decreases cortical bone mineral density (BMD) and induces development of pathologic fractures in asthmatic patients. To investigate cortical bone porosity due to glucocorticoids, we studied cortical bone volume, BMD, bone strength, and fractures in patients with asthma in this report. A total of 82 postmenopausal asthmatic patients were enrolled in the study. Vertebral fractures were diagnosed via plain spinal radiograms. Peripheral quantitative computed tomography (pQCT) was used to measure cortical BMD, relative cortical volume, and Strength Strain Index (SSI). Multiple regression analysis, Student's t test, and other statistical analyses were performed. Patients with systemic glucocorticoids therapy had lower cortical BMD, relative cortical volume, SSI, and more number of vertebral fractures than patients without it. Lifetime cumulative dose of glucocorticoids was related to cortical BMD, relative cortical volume, SSI, and the number of vertebral fractures. The cortical volumedensity relationship appeared to remain constant regardless of systemic glucocorticoid administration. The number of vertebral fractures correlated highly with cortical BMD, relative cortical volume, and SSI at the radius. In conclusion, systemic glucocorticoid administration decreases cortical bone density, cortical bone volume, and bone strength. G lucocorticoid administration appears to be responsible for the process of cortical bone porosity at both endosteal and intracortical sites. Given that both cortical bone density and volume provide bone strength, cortical bone porosity was seen to contribute to glucocorticoid - induced bone strength loss and fractures.

【目的】骨強度には皮質骨の状態が主に関与するため，全身ステロイド療法に伴う病的骨折と皮質骨障害について検討した。【方法】閉経後女性気管支喘息患者82例で，ステロイド依存性群と非依 存群において，椎体骨折数，槙骨皮質骨骨密度，皮質骨容量，骨強度（SSI）をⅩ線側面像とpQCTを用いて検討した。 【結果】ステロイド依存群はステロイド非依存群に比べて，椎体圧迫骨折数は有意に多く，榛骨皮質骨骨密度，皮質骨容積比，骨強度は各々有意に低下していた。また，皮質骨骨密度と容積は一定の割合で減少していた。椎体圧迫骨折数は皮質骨骨密度，皮質骨容積比，骨強度の全てと高い相関を認めた。 【結論】ステロイド依存性気管支暗息症例においては，皮質骨の骨 密度と容量が同時に減少して骨強度が減少することによって，病的骨折が発症すると考えられた。