NEW DIAGNOSTIC-TESTS FOR CUSHINGS-SYNDROME - USES OF NALOXONE, VASOPRESSIN AND ALPRAZOLAM

1. We set out to investigate whether the administration of naloxone al one, naloxone plus vasopressin (AVP) or naloxone plus alprazolam to pa tients with Gushing's syndrome would result in a blunted dynamic respo nse of the pituitary-adrenal axis compared with normal volunteers, Gus hing's syndrome is often difficult to diagnose, It would be helpful if new tests were available to help in the biochemical distinction betwe en Cushing's syndrome and non-Gushing's syndrome patients, 2. Naloxone testing correctly distinguished all seven patients with Gushing's syn drome (four pituitary Gushing's, two adrenal adenomas, one ectopic ACT H) from normal. Six patients were distinguished by the per cent change of plasma ACTH from basal being less than the normal range of 10 volu nteers, The seventh patient (a pituitary Gushing's) was distinguished by the per cent change from basal of plasma cortisol being less than t he normal range, 3. Naloxone plus AVP testing of two of four patients with pituitary Gushing's showed a smaller per cent change for both ACT H and cortisol compared with five normal volunteers, correctly disting uishing Gushing's from the normals, 4. Naloxone plus alprazolam did no t distinguish Gushing's from normal, 5. Naloxone testing and naloxone plus AVP testing appear to be promising methods of distinguishing Gush ing's syndrome from normal, Further experience with these tests, espec ially with obese and pseudo-Gushing's individuals, will be necessary t o determine their place in the diagnosis and differential diagnosis of the cause of Gushing's syndrome.