Altered serum levels of thyroxine, triiodothyronines and diiodothyronines in endogenous depression

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Abstract
Serum levels of thyroxine (T4), 3,3'',5-triiodothyronine (T3), 3,3'',5''-triiodothyronine (rT3), 3,5-diiodothyronine (3,5-T2), 3,3''-diiodothyronine (3,3''-T2) and 3'',5''-diiodothyronine (3'',5''-T2) were studied in 80 patients with endogenous depression before and after electroconclusive treatment (ECT). Compared to the values found after recovery, the patients when depressed had significant increased serum levels of T4, rT3, 3,3''-T2 and 3'',5''-T2. Serum concentrations of T3 and 3,5-T2 were not significantly altered. Similarly the free T4 index (FT4I) was increased, while the free T3 index (FT3I) was unaffected. Previous studies showed a reduced TSH [thyrotropin] response to TRH [thyroliberin] in patients with endogenous depression and that the long-term outcome after ECT is strongly related to changes in the TSH response to TRH (n = 23) had a pattern of serum iodothyronine concentrations similar to those (n = 57) with an unchanged TSH response. A similar pattern was also found in 7 patients with nonendogenous psychosis, in whom the TSH response to TRH was unchanged after recovery. Apparently the alterations of the TSH response to TRH found in endogenous depression cannot be explained by changes of FT4I or FT3I.