Altered thyroid hormone profile in patients with Alzheimer's disease. (November 2020)

• Record Type: Journal Article
• Authors: Quinlan, Patrick; Horvath, Alexandra; Eckerström, Carl; Wallin, Anders; Svensson, Johan
• Is Part Of: Psychoneuroendocrinology. Volume 121(2020)
• Publication Date: 2020-11
• Subjects: Thyroid hormones -- Serum -- Cerebrospinal fluid -- Aβ1-42 -- Tau -- MRI volumetry -- TDP-43 -- Dementia; Psychoneuroendocrinology -- Periodicals; Endocrinology -- Periodicals; Neurology -- Periodicals; Psychiatry -- Periodicals; Neuropsychoendocrinologie -- Périodiques; 616.8
• DOI: 10.1016/j.psyneuen.2020.104844
• Languages: English
• ISSNs: 0306-4530

Abstract

Highlights: A cross-sectional study of 36 AD patients and 34 healthy controls. Serum free T4 was moderately elevated in mild AD dementia. Decreased serum T3/T4 ratios suggest reduced peripheral deiodination in AD. Cerebrospinal fluid levels of thyroid hormone were unchanged in AD. Serum T3 levels were associated with larger hippocampal and amygdalar volumes. Abstract: Background: Epidemiological studies have linked higher levels of thyroid hormones (THs) to increased risk of Alzheimer's disease (AD), whereas in advanced AD, THs have been unchanged or even decreased. In early AD dementia, little is known whether THs are related to AD neuropathology or brain morphology. Methods: This was a cross-sectional study of 36 euthyroid AD patients and 34 healthy controls recruited at a single memory clinic. Levels of THs were measured in serum and cerebrospinal fluid (CSF). In addition, we determined AD biomarkers (amyloid-β1−42, total tau and phosphorylated tau) in CSF and hippocampal and amygdalar volumes using magnetic resonance imaging. Results: Serum free thyroxine (FT4) levels were elevated, whereas serum free triiodothyronine (FT3)/FT4 and total T3 (TT3)/total T4 (TT4) ratios were decreased, in AD patients compared to controls. In addition, serum TT4 was marginally higher in AD (p = 0.05 vs. the controls). Other TH levels in serum as well as CSF concentrations of THs were similar in both groups, and there were no correlations between THs and CSF AD biomarkers. However, serum FT3 correlated positively with left amygdalar volume in AD patients and serum TT3 correlated positively with left and right hippocampal volume in controls. Conclusions: Thyroid hormones were moderately altered in mild AD dementia with increased serum FT4, and in addition, the reduced T3/T4 ratios may suggest decreased peripheral conversion of T4 to T3. Furthermore, serum T3 levels were related to brain structures involved in AD development.