T3 Blood Levels and Treatment Outcome in Depression

Objective: We examined the correlation between the basal triiodothyronine resin uptake (T3-RU) levels in depressed subjects and the response to antidepressant treatment. Method: We treated with fluoxetine 235 outpatients meeting DSM-IV criteria for major depression. We measured T3 resin uptake (T3-RU) levels before the onset of treatment. The 17-item Hamilton Rating Scale for Depression (Ham-D-17) was administered before, during and after the eight weeks of treatment to assess changes in depressive symptoms. Results: 16 patients (6.8 percent) had low T3-RU levels (range 16.5–21), and 7 patients (3.0 percent) had high T3-RU levels (range 36–38). No relationship was found between T3-RU levels and clinical improvement, defined as either total Ham-D-17 score change or Ham-D-17 score ≤ 7 in the last 3 weeks of treatment, even after adjusting for baseline severity of depression. Conclusion: Abnormal T3-RU levels are rather uncommon in outpatient depression and do not correlate with the response to antidepressant treatment or lack thereof.