According to other studies, several factors may contribute to the high incidence of anemia in CD patients: (1) vitamin B12 and folate deficiency resulting from severe small intestine inflammation or following ileocolectomy; (2) hepcidin upregulation due to increased cytokine production, which inhibits intestinal iron absorption; (3) medications such as thiopurines and methotrexate, which suppress erythropoiesis; and (4) chronic blood loss from uncontrolled disease activity (8). This evidence concerns the gene HAMP and anemia (phenotype).