To analyze immunoreactivity to CaSR synthetic peptides 41–69, 114–126, 214–238, 344–358, and 374–391, sera from 14 APS1 patients, 1 AHH patient (3 separate serum samples), and 10 healthy controls were tested in an ELISA format. This evidence concerns the gene CASR and Autoimmune polyendocrinopathy type 1.