TRH tests with analyses of TSH, prolactin, and GH responses in subtypes of patients with major depressive disorders

TRH tests were performed on 131 patients with RDC diagnoses of major depressive disorders to study altered endocrine control mechanisms in subtypes of depression. The TSH response to TRH was measured in all patients. In more than a third of the sample the prolactin (PRL) and growth hormone (GH) responses were also analysed. There were no differences between bipolar, primary unipolar and secondary unipolar patients in means of any endocrine variable. However, the expected positive correlation between baseline TSH and delta TSH was absent in the secondary unipolar group, indicating a dysregulation of pituitary TRH receptor sensitivity in this depressive subtype. Only delta TSH was dependent on depressive state, being lower in currently ill primary unipolar patients only. Patients with melancholic features (endogeneity scores high) had blunted TSH responses. Weight loss was connected with TSH blunting in all depressive subtypes. Among patients with blunted delta TSH (less than 5 mU/l) there was no relationship between degree of weight loss and delta TSH. Further, examination of partial correlation coefficients suggests weight loss of affect delta TSH by virtue of its being part of the melancholic syndrome. A significant correlation between blunted delta TSH and nonsuppression of cortisol in the DST was found only among primary unipolar patients, arguing for some independence of the TRH test and the DST in mirroring disturbed endocrine controls in depression.