Selenium-75-cholesterol imaging and computed tomography of the adrenal glands in differentiating the cause of Cushing's syndrome.

Measurement of 75Se-cholesterol (Scintadren) uptake and computed tomography (CT) of the adrenal glands were compared as a means of differentiating the cause of Cushing's syndrome in 11 patients over a 2-year period. Quantitative Scintadren imaging differentiated adrenocorticotrophic hormone (ACTH)-dependent disease from local adrenocortical lesions as the cause of Cushing's syndrome in all the patients studied. CT of the adrenal glands rapidly and accurately detected the adrenal mass lesions in 2 cases and was effective in documenting bilateral hyperplasia due to ectopic ACTH-dependent disease. However, in entopic ACTH (pituitary)-dependent disease the adrenal glands were of normal thickness in all but 2 patients, who had bilateral hyperplasia. Scintadren imaging and CT are useful non-invasive procedures for differentiating local adrenal disease from ACTH-dependent disease as the cause of Cushing's syndrome and should be the initial investigations once a firm clinical and biochemical diagnosis of Cushing's syndrome has been made.