Although the TTR concentration in CSF (90 to 360 nM) is higher than Aβ (Aβ40 981 ± 409 pM and Aβ42 73.6 ± 41.8 pM) [42,57,58], several studies report that TTR levels are diminished among AD patients when compared to controls [59], both in the CSF and plasma [60,61]. Here, TTR is linked to Alzheimer disease.