A comparative study of the pituitary TSH response to thyrotropin in outpatient depressives.

The pituitary thyroid-stimulating hormone (TSH) response to exogenous thyrotropin-releasing hormone (TRH) has been reported abnormal in depression, chiefly in endogenous depression among inpatients. This study finds an incidence of abnormality among a group of 53 outpatients that is no greater than among controls. Among outpatients with either major depression by Research Diagnostic Criteria (RDC) or atypical depression by our criteria, blunted responses are no more common than among normal controls. A comparison group of inpatient RDC major depressives, endogenous subtype, shows a significantly higher proportion of abnormal or blunted responses. These data suggest that the test may be less useful among outpatients than among inpatients. The test does detect a significant but unexplained biologic abnormality among inpatient endogenous depressives.