Moreover, limited Information is currently available about the relationship between thyroid hormones and brain tau deposition, another key pathology of AD: While a cross-sectional study with a small population (comprising 36 euthyroid AD dementia patients and 34 healthy controls) reported no association between serum thyroid hormones and CSF tau levels [11], no other studies have yet investigated the association of serum thyroid hormones with in vivo brain tau deposition as measured by PET examination. Here, MAPT is linked to Alzheimer disease.