o Top 2 causes: pregnancy and chronic blood loss
o Dietary deficiency: eating disorders, pica, poor diet, poverty
o Impaired absorption: sprue, fat absorption disorders, chronic diarrhea, gastric bypass
o Increased requirement: infants, adolescents, pregnancy (for rapid growth)
o Chronic blood loss: medications NSAIDS, menorrhagia, ulcers, hiatal hernia, varices, cirrhosis, hemorrhoids, ulcerative colitis, cancer
-GENETIC: rare
o Transmembrane protease serine 6 (TMPRSS6) gene mutation
o TMPRSS6 negatively regulates hepcidin
o Hepcidin: hormone regulates iron absorption
o The TMPRSS6 expression is also down-regulated by inflammation
