Thyroid-stimulating hormone and the risk of Alzheimer's disease: an ADNI cohort study

Abstract

Background: The association of thyroid function with Alzheimer's disease (AD) is controversial. This study mainly aimed to investigate the association between thyroid-stimulating hormone (TSH) and the risk of AD. Methods: We investigated the cross-sectional association between TSH and cognition, cerebrospinal fluid (CSF) biomarkers, and neuroimaging by linear regression models. The association between TSH and the risk of MCI conversion to AD within four years was measured by Cox proportional hazards models. Additionally, we investigated the interaction effects between TSH and sex in analyses. Results: A total of 476 participants who measured plasma TSH at baseline were included in the analyses, comprising 49 cognitively normal (CN), 336 mild cognitive impairment (MCI), and 91 AD. Within four years of follow-up, 160 MCI participants converted to AD. No associations were found between TSH and cognition and AD biomarkers. There existed sex differences in the association between TSH within the normal range and the risk of AD (p for interaction = 0.043). The highest tertile of TSH within the normal range significantly increased the risk of AD in female compared to the lowest tertile (HR = 2.62, p = 0.021). TSH was not associated with the risk of AD in male. Conclusions: High plasma levels of TSH within the normal range were associated with an increased risk of AD in female but not in male.