Neuroendocrine interrelationships in major depressive disorder.

The authors administered the thyrotropin-releasing hormone (TRH) stimulation test and the dexamethasone suppression test (DST) to 54 patients who met DSM-III criteria for major depressive disorder and to 19 nondepressed patients. A blunted thyrotropin (TSH) response to TRH injection was noted in 18 depressed patients (33%) but in no nondepressed patients. An escape from dexamethasone suppression was noted in 23 depressed patients (43%) but in only 2 nondepressed patients (11%). The combined sensitivity of the DST and the TRH test in identifying major depressive disorder was 67% with 92% specificity. Only 6 depressed patients (11%) had abnormal responses to both the DST and the TRH test, suggesting that the hypothalamic-pituitary-adrenal axis dysregulation and hypothalamic-pituitary-thyroid axis dysregulation are independent phenomena. These findings support the combined use of these neuroendocrine tests in clinical practice.