Thyroid function in patients maintained on lithium.

To determine the clinical significance of thyroid function abnormalities in patients maintained on lithium, the authors evaluated the relationships of thyroid function tests to clinical response to lithium and side effects from lithium in 20 outpatients meeting DSM-III criteria for major affective disorder. No significant relationships were found between baseline thyroid function tests and clinical response. Thyroxine (T4) and triiodothyronine uptake ratio (T3UR) within the normal range were found to be associated with complaints of lethargy and cognitive impairment. Thirteen subjects were followed prospectively for 6 months with monthly evaluations of affective state, side effects, and occurrence of relapse. Thyroid function tests were repeated at the final visit. Final and mean T3 levels within the normal range were found to be significantly lower in patients who relapsed, and mean T3 level was inversely correlated with affective state as measured by mean scores on the Hamilton Rating Scale for Depression and the Young Mania Rating Scale.