Thyroid hormones and cognitive functioning in healthy, euthyroid women: A correlational study

Abstract

Thyroid hormones (THs) play a critical role in differentiation, growth, and metabolism of animal and human organ systems, including the brain. Although associations between normal levels of THs and cognitive functions in healthy elderly individuals have been reported, the findings are inconsistent, possibly due to differences in study designs. Because thyroid disease occurs more frequently in women, the goal of the present study was to examine the relationship between levels of THs and performance on neuropsychological tests in 122 healthy, euthyroid women whose mean age was 51 years. Higher levels of free T3 were positively associated with longer completion times (slower performance) on Trail Making Test -Part A (p=0.006) and Part B (p=0.032) and on the Tower of London test (p=0.002). Higher levels of thyroglobulin antibodies (TgAb) were positively correlated with more errors on the Trail Making Test Part B (p=0.000), on the Word Fluency test (p=0.023), and on the Design Fluency test (p=0.045). No significant correlations between TH levels and scores on mood, verbal memory, or working memory measures were observed. The findings point to a possible link between THs and cognitive processes that are mediated primarily by frontal cortex, areas associated with executive function tasks, and suggest that elevations in levels of free T3 and TgAB within the normal range may negatively influence executive functions.

Modele funkcji poznawczych względem wybranych parametrów stanu funkcjonalnego tarczycy u kobiet po menopauzie

“…It was observed that higher concentrations of anti-thyroglobulin antibodies positively correlated with a larger number of mistakes in the Trial Making Test Part B, in the Word Fluency test, and in the Design Fluency test. The researchers suggest that a higher concentration of TgAB, but within normal values, may exert a negative effect on executive functions, which was not confirmed in our own study [43]. Many other studies confirm the negative effect of high titres of anti-thyroglobulin and anti-thyroid peroxidase antibodies on the results of cognitive functions [44,45].…”

Cognitive function in Hashimoto’s thyroiditis under levothyroxine treatment

“…2 This is not the case for subclinical hypothyroidism and euthyroid HT, whether under levothyroxine (LT4) treatment or not, the effect of which on cognitive performance is somewhat controversial. Whereas it has been suggested that "a state of brain hypothyroidism in the context of systemic euthyroidism" 3 and an association between thyroid autoimmunity and cognitive function may exist, 4 and that neurocognitive functioning and psychological well-being may not be completely restored in patients with hypothyroidism despite LT4 treatment, 5 neither was an association between indices of depression and thyroid autoimmunity established in a population study 6 nor did treatment with levothyroxine for a year improve any parameters of cognitive functioning in patients with subclinical hypothyroidism. 7 Our aim was to test: 1) whether LT4 treatment improves the profile of first degree relatives as to different aspects of cognition and emotion, and 2) whether euthyroidism under LT4 treatment (and manifesting with depressive symptomatology) leads to neuropsychological deficits.…”

Effect of Thyroid Function Variations Within the Laboratory Reference Range on Health Status, Mood, and Cognition in Levothyroxine-Treated Subjects

“…In euthyroid subjects without thyroid disease, depression, anxiety, or cognitive decrements have been linked to variations in TSH or free thyroxine (fT4) levels (4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17). However, the correlations have shown improvements or decrements with higher or lower thyroid function, depending on the report.…”