Cushing's Osteoporosis Specificities

Osteoporosis induced by glucocorticoids excess constitutes the main cause of secondary osteoporosis. Most of data available are provided from cohort studies of patients treated by corticosteroids, affecting among 1% of population. In contrast, very few data on osteoporosis are available in the Cushing syndrome (CS), a rare disease affecting 1 or 2 million of inhabitants, and characterized by an endogen glucocorticoid excess production. This affection is responsable of frequent fractures, occuring in 30-60% of patients (vertebral asymptomatic in 50% of case, hip, ribs). Fractures occurs often frequently above the threshold usually used for osteoporosis (T-score\<-2.5), most often in the range of osteopenia. These data suggest that surface bone density isn't sufficient to characterize bone fragility, architectural factors are probably involved, and should be evaluated. The specificity of osteoporosis induced by endogen glucocorticoids excess in comparison with osteoporosis induced by estrogenic deficiency in post-menopausal women is poorly known, especially in endogen glucocorticoid excess. A recent microarchitecture studies showed alterations of cortical compartment in patients with Cushing's syndrome, confirming by our preliminary preclinical data from a transgenic murin model of Cushing's syndrome. In these ten last years, new radiologic tools have been developped, and are able to evaluate bone architecture. The peripheral Quantitative Computed analyses the bone architecture with distinction between cortical and trabecular compartment. Therefore, we aim to determine the specificity of osteoporosis induced by glucocorticoids excess in comparison to post menopausal osteoporosis thanks to pQCT analysis.