We analyzed the levels of islet amyloid polypeptide/amylin (IAPP) and its prohormone—proamylin (proIAPP)—substances influencing the mechanisms of carbohydrate metabolism [15,16,17,18]; chromogranin A (ChA)—a supposed autoantigen in T1D [19,20,21]; and the product of its proteolysis catestatin (CST) [22,23], intestinal fatty acid binding protein (I-FABP)—a protein responsible for increased permeability of intestinal epithelial cells, showed to be increased in children with T1D [24]. The gene discussed is TCFL5; the disease is type 1 diabetes mellitus.