Comparison of thyroid function between responders and nonresponders to thyroid hormone supplementation in depression

The serum levels of thyroxine (T4), 3,5,3'-triiodothyronine (T3) and 3,3',5'-triiodothyronine (reverse T3, rT3) were examined from 8 depressed patients who did not maximally benefit from conventional antidepressant therapy. Four of the 8 depressed patients showed significant clinical improvement after thyroid hormone was added to their ongoing antidepressant drugs. The T4 and rT3 levels prior to thyroid hormone supplementation were significantly lower in responders than in nonresponders, although within the normal range. Furthermore, all of the patients who had both their rT3 levels less than 200 pg/ml and T4 levels less than 7 micrograms/dl responded to the thyroid hormone treatment. These data suggest that the lower T4 and rT3 levels can predict the treatment response to the thyroid hormone supplementation in depressed patients.