A 56-year-old female patient was admitted to our hospital because she was suffering from severe osteoporosis. The patient had experienced repeated spontaneous fractures for 1.5 years such as serial rib fractures, fractures of the sternum and most recently fracture of the neck of the femur after a minimal trauma. Histology revealed a low-turnover-osteoporosis. Subsequent radiologic examination showed extreme osteoporosis of the skeleton with numerous compression fractures of the vertebral bodies as the most outstanding finding. The bone histology and the relatively short history of spontaneous fractures led us to investigate endogenous hypercortisolism as a possible cause although clinical signs were absent. An attenuated diurnal variation of cortisol levels and lack of suppressibility of cortisol was found. Furthermore, magnetic resonance tomography showed a microadenoma of the pituitary gland. Computerized tomography of the adrenals was normal. Transsphenoidal surgery confirmed the tentative diagnosis and histological examination revealed a bilateral adenoma of the pituitary gland.