Thyrotrophin response to thyrotrophin-releasing hormone in unipolar and bipolar affective illness

The plasma levels of thyrotrophin (TSH) and the response of this hormone to 200 microgram of thyrotrophin-releasing hormone (TRH) were studied in 27 unipolar and 24 bipolar depressive patients before and after amitriptyline treatment as well as in 42 normal controls. There was no significant difference in basal TSH levels between any of the groups studied according to diagnosis, menopausal status and antidepressant treatment. Before treatment, the TSH response to TRH was significantly lower in the unipolar and bipolar depressive patients than in normal controls. The TSH response to TRH did not differ significantly between the unipolar and bipolar depressives. When menopausal status was taken into account, the TSH response to TRH was significantly blunted in the unipolar postmenopausal patients when compared to postmenopausal controls. In the bipolar group, the premenopausal depressive patients had a significantly lower TSH response to TRH than premenopausal controls. After amitriptyline treatment, the TSH response to TRH, which was impaired before treatment in the bipolar premenopausal patients, improved significantly. However, no significant difference in the TSH response to TRH could be demonstrated after treatment in the unipolar postmenopausal patients in whom the TSH response was blunted before treatment. Our findings suggest that the differential TSH response to TRH in unipolar and bipolar patients may constitute biological markers of endocrine dysfunction in clinical subgroups of affective disorders.