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The authors sought to determine whether the performance of the dexamethasone suppression test (DST) could be enhanced by expressing cortisol as a function of dexamethasone. Because cortisol concentration is a function of the reciprocal of dexamethasone concentration, this relationship was approximated by calculating the product of cortisol and dexamethasone as a dexamethasone suppression index. Preliminary assessment of test performance measures (sensitivity, specificity, and predictive power) showed that use of the dexamethasone suppression index was an improvement over the use of cortisol levels alone. Factoring dexamethasone levels into post-dexamethasone cortisol level measures may enhance the utility of neuroendocrine assessment in psychiatry.

Biological markers of affective disorders have not been studied intensively in patients with secondary depression. An elderly woman with severe delusional depression secondary to thyrotoxicosis was monitored with weekly dexamethasone suppression tests (DSTs) and three sleep electroencephalography (EEG) evaluations. She received treatment only for her thyrotoxicosis, but her depression resolved completely. The serial DSTs were normal throughout her depression, consistent with the specificity of this test for primary endogenous depression. The sleep EEG erroneously suggested a diagnosis of primary depression but effectively monitored clinical improvement. Biological markers may have applicability in evaluating and monitoring patients with secondary depression.

The authors performed dexamethasone suppression tests (DST), TRH infusions, 72-hour urine collections, and lumbar punctures on a group of male depressed patients. Approximately 60% of the patients were DST positive and 33% had a blunted TSH response. Two biologic variables, the 8 a.m. postdexamethasone cortisol and the postprobenecid CSF 5-hydroxyindoleacetic acid (5-HIAA), accounted for over half of the variance in the behavioral measure, the Hamilton score. Plasma cortisol elevation was associated with high 3-methoxy-4-hydroxyphenyl glycol (MHPG) excretion; TSH blunting was associated with low urinary MHPG excretion. Comprehensive biologic measures showed certain significant interrelationships and correlations with the severity of depression.

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.

Dexamethasone suppression tests (DSTs) were performed for 18 moderately demented elderly patients, 66 depressed elderly outpatients, and 25 age- and sex-matched healthy elderly control subjects. Seventeen percent of the demented patients and 4% of the normal subjects were DST nonsuppressors, compared to 38% of the total depressed group. The postdexamethasone plasma cortisol levels of the dementia group fell between those of the normal and the depressed subjects. In addition, demented patients had postdexamethasone cortisol levels significantly lower than those of depressed patients with high Hamilton depression scores. Older subjects in all diagnostic categories, including normal subjects, had higher postdexamethasone plasma cortisol levels.

Dexamethasone suppression tests were given to 69 consecutively admitted psychiatric patients. Nonsuppression rates for depression with or without melancholia and for schizophrenia were similar to those previously reported, but for mania and other psychoses the frequencies were higher than expected.

Dexamethasone suppression tests were given to 10 patients with panic disorder and 22 depressed patients. All patients with panic disorder were normal suppressors, and nine depressed patients were nonsuppressors. The mean cortisol levels of the two groups differed significantly.

The author performed weekly dexamethasone suppression tests on five nondepressed male chronic schizophrenic patients over 12 weeks. Nonsuppression occurred three times in two patients, twice in two patients, and once in one patient.

Two patients treated with alprazolam for panic disorder and agoraphobia developed a manic episode. Two biological markers--shortened REM latency and nonsuppression on the dexamethasone suppression test--suggested that both patients may have had an underlying affective disorder.