The Relationship Between Thyroid Status, Cortisol Level, Cognition And Neuropsychiatric Symptoms In Patients With Alzheimer Disease

Abstract

Objective: Growing evidence suggests an association between alterations in thyroid function and cortisol level and the pathogenesis and progression of Alzheimer disease (AD). The aim of this study was to investigate whether these hormones are related to the cognitive and neuropsychiatric manifestations in the patients with AD. Methods: This was a cross-sectional, case control study. Cortisol level and thyroid status were evaluated in 40 outpatients with mild to moderate AD and 20 normal controls, and cognitive and neuropsychiatric assessments were performed using the Cognitive Ability Screening Instrument (CASI), Neuropsychiatric Inventory, and Geriatric Depression Scale. Results: The patients had worse cognitive function and lower free triiodothyronine (FT3) level than the controls. Those with aberrant motor behavior had a lower FT3 level, and those with dysphoria had a higher cortisol level than those without these symptoms. The patients with a higher level of FT3 also had higher concentration and abstract thinking/judgment scores on the CASI, and those with a higher level of cortisol were associated with a decline in global cognition. Conclusion: Our results indicate a possible association between thyroid hormones and neuropsychiatric manifestations as well as cognitive function in euthyroid patients with AD, and suggest the potential efficacy of adjunctive T3 treatment in these patients. We hypothesize that patients with dysphoria subjectively experience more stress. Further studies are needed to elucidate whether this would increase the risk of depression or exacerbate cognitive function, and to investigate whether a non-pharmacological approach can relieve dysphoria symptoms according to the psychological attachment theory.