Osteoporosis is more prevalent in adrenal than in pituitary Cushing's syndrome

Osteoporosis is the most common complication of Cushing's syndrome. We retrospectively examined the prevalence and risk factors for osteoporosis in 42 female patients with Cushing's syndrome. Osteoporosis and atraumatic fractures were assessed by bone mineral density of the lumbar vertebral spine (L2-L4) using dual energy X-ray absorptiometry (DXA) and X-ray examination. The prevalence of osteoporosis and fracture were 54.8% and 21.4%, respectively. The prevalence of osteoporosis (69.6% vs. 37.8%) and atraumatic bone fracture (26.1% vs. 15.8%) were significantly higher in patients with adrenal Cushing's than in those with pituitary Cushing's. AP and lateral BMD was significantly higher in patients with pituitary origin than in those with adrenal origin. Among several variables examined by multiple logistic regression, the etiology of Cushing's syndrome (adrenal vs. pituitary origin) was a significant factor affecting the prevalence of osteoporosis. Neither age, body mass index, duration of amenorrhea, nor extent of hypercortisolism were significant factors in this analysis. Plasma DHEA-S and urinary 17-KS excretion were significantly higher in pituitary Cushing's than in adrenal Cushing's. The present study shows that the prevalence of osteoporosis in patients with Cushing's syndrome is influenced by its etiology. A factor associated with pituitary Cushing's syndrome, such as adrenal androgen, may protect these patients from glucocorticoid-induced osteoporosis.