In order to enrich immunoreactive peptides recognized by anti-CaSR antibodies, the CaSR peptide phage-display library was immunoscreened in biopanning experiments with sera from 14 APS1 patients, 1 AHH patient, and 2 controls, as well as with anti-CaSR antibodies as positive controls. Here, CASR is linked to Autoimmune polyendocrinopathy type 1.