In the present study, using a quantitative SRM proteomic assay, we identified and quantified the translated protein levels of two novel IAPP isoforms: hIAPPβ, which was increased in the cerebrum and reduced in the plasma of AD patients, and hIAPPγ, which encodes a novel mature IAPP that is 25-AA in length, is nonamyloidogenic, and was found to be reduced in T2DM islets and in the plasma of AD patients. Here, IAPP is linked to Alzheimer disease.