The combined T3/TRH-test in depressed patients and healthy controls

In the present study, we investigated whether pre-treatment with triiodothyronine (T3) is able to suppress the TRH-induced TSH response in depressed patients. In 20 depressed patients (8 men, 12 women) suffering from Major Depression according to DSM-IV criteria and in 20 age- and sex-matched healthy controls the single TRH-stimulation test was carried out followed by a combined T3/TRH-test (pre-treatment with 40µg T3 at 23: 00h the night before). After four weeks of treatment with sertraline, the single TRH-test and the combined T3/TRH-test were performed again in the patients. Compared to controls, the depressed patients showed a blunted TSH-response in the single TRH-test. However, the suppression of TRH-induced TSH-response after pre-treatment with T3 was comparable in patients and controls. 4-week treatment with sertraline did not have any impact on the outcome in the single TRH-test and the combined T3/TRH-test. Apparently, no disturbance of feedback control in regulation of hypothalamo-pituitary-thyroid axis secretion can be demonstrated in depressed patients when using the combined T3/TRH-test.