PTPN22 and Cowden disease: More specifically, CD 40 is shared by Graves’ disease and inflammatory bowel disease (IBD), CTLA-4 is shared by Graves’ disease, HD, IBD and CD, HLA genes are shared by Graves’ disease, HT and CD, and finally PTPN22 is shared by CD, Graves’ disease, HT and IBD, thus enhancing the genetic cross-talks in the gut-thyroid axis (18).