Cognitive functions and mood during chronic thyrotropin-suppressive therapy with L-thyroxine in patients with...

Subclinical thyroid dysfunctions may cause cognitive deficits and mood disorders. Chronic TSH-suppressive therapy with L-T(4) causing subclinical hyperthyroidism has been widely used in treatment of patients with thyroid differentiated carcinoma. The impact of this therapy on cognitive functions and mood have not been systematically studied. The aim of this study was to asses executive functions, working memory, attention, and depression in patients with subclinical hyperthyroidism in the course of TSH-suppressive therapy.

Thirty-one patients with subclinical hyperthyroidism in the course of suppressive treatment with L-T(4) following the total thyroidectomy and radioiodine ablative therapy were included in the study. Cognitive functioning in patients and control group were investigated using the battery of neuropsychological tests [Wisconsin Card Sorting Test (WCST), The Oral Word Association Test (OWAT), Trail Making Test, The Stroop Color-Word Interference test and Digit span]. Psychometric evaluation was performed using 17-items the Hamilton Depression Rating Scale (HDRS) and Beck Depression Inventory (BDI).

The performance on tests assessed executive functions, psychomotor speed, and attention was significantly lower in patients group. There was no differences in results of Stroop test and Digit Span forward and backwards between both groups. The intensity of depressive symptoms negatively correlated with a number of completed categories on WCST and results of OWAT. Cognitive deficits were still observed when patients with concomitant general medical conditions and depression were excluded from the analysis.

Our findings provide evidence of neuropsychological impairment in patients with differentiated thyroid carcinoma treated with chronic TSH-suppressive therapy.