Free triiodothyronine (T 3) and thyroxine (T 4) in a group of unipolar depressed patients and normal subjects

We examined levels of free triiodothyronine (fT 3) and free thyroxine (fT 4) in serum from a group of 32 patients with unipolar major depression and 46 normal control subjects using the Amerlex (Amersham, Arlington Heights, IL) RIA procedures for these hormones. Free T 3 levels were significantly lower ( p < 0.004) in the depressed patients as a group (5.02 ± 1.01 pmol/L, mean ± SD) than in the normal control subjects (5.74 ± 1.23 pmol/L). Free T 3 levels were lower ( p < 0.01) in depressed men (5.25 ± 1.43 pmol/L) when compared with male control subjects (6.46 ± 1.01 pmol/L). Depressed women (4.78 ± 0.60 pmol/L) also had lower T 3 levels than did the female control subjects (5.09 ± 1.06 pmol/L), but the difference was not statistically significant. Lower fT 3 levels were also observed in melacholic depressed patients when compared with nonmelancholic depressed patients or when compared with normal control subjects. No differences in fT 4 were observed between groups in this study.