Low thyroid-stimulating hormone as an independent risk factor for Alzheimer disease

To assess a possible relationship between thyroid-stimulating hormone (TSH) levels, vascular risk factors, and Alzheimer disease (AD). TSH levels were measured in 178 AD patients (35 confirmed post mortem) and 291 cognitively screened control subjects who were all euthyroid (TSH: 0.5 to 6 mU/L). The risk of AD was determined in participants with lower levels of TSH, several cerebrovascular risk factors, and other potential confounds. AD patients had significantly lower levels of TSH than control subjects. Lowered TSH was associated with a more than twofold increased risk of AD (odds ratio = 2.36, 95% CI = 1.19 to 4.67), independent of other risk factors. Lowered TSH within the normal range is a risk factor for AD, independent of several cerebrovascular risk factors and confounding variables.