Dexamethasone suppression test and TRH test in endogenous depression

Dexamethasone suppression test (DST) and thyrotropin releasing hormone (TRH) stimulation test were performed in 34 patients with endogenous depression. Compared with 33 psychiatric controls (limit of discrimination for serum cortisol of 275 nmol/l = 10 micrograms/100 ml) the specificity of the DST was 91% and the sensitivity was 65%. Compared with 24 healthy subjects the sensitivity of the TRH test was 24%, and the combined sensitivity for the DST and the TRH test was 76%. In contrast to the TRH test the DST showed a significant relationship (r = 0.54, P less than 0.01) to the Hamilton Rating Score. Repeating the tests after clinical recovery parallel changes of the two tests were found in 14 of 19 patients with abnormal DST in the depressed phase. In the remaining five patients the DST normalized, while the TRH test remained unchanged. It is suggested that both the apparent higher diagnostic sensitivity and the higher rate of normalization after clinical recovery of the DST is due to the dependency of the severity of depression.