Specificity of the combined dexamethasone suppression and TRH/TSH tests in melancholia

Subjects for this study were 61 acute psychiatric inpatients. Forty two (42) qualified for a RDC diagnosis of Major Depressive Disorder (MDD) and 19 for other disorders. After a 7-10 days drug withdrawal period patients were subjected to the dexamethasone suppression and TRH/TSH tests. TSH was measured using a RIA. Cortisol was measured using a CPB technique. Eighteen (18) of the 42 MDD patients and 1 of the 19 others had an abnormal DST (sensitivity 43%, specificity 94%). Twenty two (22) depressed patients and 4 others had a blunted TSH response (sensitivity 52%, specificity 79%). Thirteen (13) depressives and none of the others had abnormal responses to both tests (sensitivity 31%, specificity 100%). DST nonsuppression alone and blunted TSH response alone were not a function of severity of illness, sex, age of onset, family history or RDC subtype. The 13 MDD patients with the combined neuroendocrine abnormality were more severely depressed, had longer episodes of illness, were older and had a later age of onset of their first episode. Our results add support to the suggestion that serial neuroendocrine challenge studies might be of particular relevance and significance in the diagnosis and management of elderly psychotic depressed patients.