Short-term hypothyroidism in thyroid cancer patients and cognitive-motor performance relevant for driving

In patients with differentiated thyroid carcinoma (DTC) who, after thyroidectomy, are to receive radioiodine therapy or diagnostics, a strong TSH stimulus is necessary. Traditionally, this is induced by thyroid hormone withdrawal (THW) over a period of 4-5weeks; alternatively thyroid hormone replacement therapy is continued and recombinant human thyrotropin (rhTSH) is administered. During the hypothyroid state due to THW, patients often report mood disturbances and physical complaints but also an impairment of performance during attention demanding tasks.

Based on physiological, self-report and performance test data collected from various studies, we proposed the hypothesis that thyroidectomized DTC patients perform significantly worse in cognitive-motor functions that are relevant for driving when in the THW-induced hypothyroid state compared to when thyroid hormone replacement therapy is continued and rhTSH is administered.

We compared 41 DTC patients (age 42.3 (9.4) years; 80.5% female) after 4weeks THW with 41 DTC patients after the application of rhTSH, pairwise matched according to age, gender and educational level, with respect to performance in 4 core tests of the Act-React-Testsystem ART-90, a validated test battery for examining fitness to drive.

Contrary to our expectations, no statistically relevant impairment of performance could be confirmed in the THW group in comparison to the rhTSH group for any variable (at adjusted α). At most there is a tendency in the THW group for slowed reaction times in simple-choice reaction tasks; the (standardized) difference to the rhTSH group is however small (d'=0.31). Furthermore, large effects due to THW, as they are suggested by several studies, could be excluded.