Relationship of thyrotropin-releasing hormone test and dexamethasone suppression test abnormalities in unipolar depression.

The thyrotropin-releasing hormone (TRH) test and the dexamethasone suppression test (DST) were administered to 50 inpatients with unipolar depression. Of the patients tested, 64% had a blunted thyroid-stimulating hormone (TSH) response to TRH and 50% failed to suppress on the DST. There was no significant association between these two abnormalities by chi-square test. This lack of association suggests that the blunted TSH response to TRH is not an artifact of hypothalamic-pituitary-adrenal hyperactivation. The TRH test and the DST complemented each other as biological markers for active unipolar depression: 30% of the patients were identified by both tests, 34% by the TRH test only, 20% by the DST only, and 16% by neither test. The two tests may be useful in developing a nosology for major unipolar depression that is based on both descriptive and neurobiological information.