Increased occurrence of weaknesses in attention testing in patients with Hashimoto’s thyroiditis compared to patients with other thyroid illnesses

Abstract

Previous studies suggest disturbances of the central nervous system (CNS) in patients with Hashimoto's thyroiditis (HT), independently of thyroid function disorders. In the present prospective study, neuropsychological testing was performed for the first time in 26 euthyroid patients with HT compared to 25 euthyroid patients undergoing hormonal treatment for goitre or after thyroid surgery. We investigated executive function, attention, visual and verbal memory as well as acoustic working memory with established neuropsychological tests and detected no significant differences between the two groups. In addition, test results were expressed as z-score which is defined as the deviation of an individual's value from the mean value of a reference population, divided by the standard deviation of the reference population. Thereby, we found significantly more HT patients with a z-score of less than -1.5 in the d2 test than in the control group (total score I, HT vs. control group: 10 vs. 3, p=0.0302; total score II, HT vs. control group: 11 vs. 1, p=0.0013). The d2 test, which measures processing speed, rule compliance, and quality of performance, allows for a neuropsychological estimation of individual attention performance. HT patients with results below the normal range in the d2 attention test showed a significant increased mean value of anti-thyroid peroxidase antibodies compared to HT patients with normal test results (371.4+/-187.2IU/l vs. 69.3+/-28.7IU/l, p<0.05). In conclusion, our results point to subtle brain dysfunction in a subgroup of patients with HT even in euthyroid state. This could either be due to an association with an unknown autoimmune disorder affecting the CNS or a pathogenetic role of thyroid antibodies themselves.