[Osteoporosis: diagnosis or sign of suspicion?]

We present the case of a fifty-year-old male who presented at the Neurology Service. During the previous months he had noticed progressive cognitive deterioration, and particularly a loss of memory and executive abilities, as well as proximal weakness of the four limbs and lumbar tenderness. He had lost ten centimetres of height. A bone densitometry was performed, which showed early osteoporosis.

The laboratory results showed an increase in urine cortisol excretion (1725 g/24h), with detectable plasma ACTH concentration (89 pg/ml), suggesting ACTH-dependent Cushing's syndrome, Additional tests were run in order to determine a hypothalamic or ectopic location of the syndrome. To this end, a bilateral inferior petrosal sinus sample (BIPSS) was performed for ACTH determination. BIPSS is the test that has been proven to have the best sensitivity to achieve differential diagnosis of ACTH-dependent Cushing's syndrome.