Thyroid Status and Cognitive Function in Euthyroid Patients with Early Parkinson's Disease

Abstract

Background: Alterations in thyroid hormone (TH) levels may be related to the pathogenesis of mild cognitive impairment (MCI) and dementia. Cognitive deficits are common in Parkinson's disease (PD) patients. The aim of this study was to investigate whether variations within the normal ranges of thyroid function are related to cognitive function in early PD without dementia. Methods: Eighty-four euthyroid patients with early PD underwent evaluation of their thyroid status, including measures of thyroid-stimulating hormone (TSH), total triiodothyronine (tT₃) and free thyroxine (fT₄), and comprehensive neuropsychological tests. Results: The 46 patients of the PD-MCI group did not differ in the serum levels of TH compared to the 38 patients of the PD-normal cognition group. fT₄ levels were inversely associated with the Mini-Mental State Examination (MMSE) score and neuropsychological tests of attention and visuospatial and executive function. TSH and tT₃ levels were not related to cognitive performances. After controlling for demographic and clinical variables, multiple regression analyses indicated statistically significant associations between fT₄ concentrations and MMSE score and neuropsychological tests of executive function. Conclusions: This study supports a relationship between the thyroid status and cognitive function in euthyroid early PD patients, with higher concentrations of fT₄ being associated with a poor performance of executive function.

Parkinson's disease and thyroid dysfunction: Effects on severity and risk of cognitive impairment Abeer A.Tony1, Emad F Kholef,2 Effat AE.Tony3, Kerollos N Helmy4, Ahmed Shoeb5

“…In contrast to our findings, Choi et al conjectured, contrary to our results, that an increase in fT4 may be more closely associated with cognitive impairment because of the significant correlations shown between fT4 concentrations and general cognition and executive function in PD patients [38]. Two studies provided evidence in favor of this hypothesis: one examined pathology and found that higher levels of total and fT4 were associated with a higher risk of Alzheimer's disease, as well as a higher number of neocortical neuritic plaques and neurofibrillary tangles [39,40].…”

“…We found a statistically significant positive link between our patients' cognitive impairment and TSH levels in the current investigation. Previous research has not been able to establish a meaningful connection between T3 and cognitive performance [38].…”

“…The other study used magnetic resonance imaging and found that high fT4 was linked to atrophy of the amygdala and hippocampus on imaging. In early PD without dementia, Choi et al hypothesize that elevated fT4 causes an increase in neocortical neuritis plaques and neurofibrillary tangles, which in turn leads to poor performance on cognitive function tests [38].…”

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

“…This researcher obtained different results with respect to fT4, finding that high normal concentrations of fT4 positively correlated with worse results in the MMSE, and deterioration of the test results by at least 4 scores within two years of observation [31]. Choi et al also noted that a higher concentration of fT4 in individuals with euthyreosis was related with worse results for executive functions [32].…”