Anemia, PerniciousIntrinsic FactorAchlorhydriaAnemiaSchilling TestVitamin B 12Anemia, MacrocyticVitamin B 12 DeficiencyCobalt IsotopesAnemia, MegaloblasticHydroxocobalaminGastrinsPostgastrectomy SyndromesParietal Cells, GastricGastric JuiceAnemia, HypochromicGastritis, AtrophicGastric MucosaGastritisAnemia, AplasticCarcinoid TumorEnterochromaffin CellsAnemia, HemolyticZollinger-Ellison SyndromeFolic Acid DeficiencyCobalt RadioisotopesAutoimmune DiseasesAutoantibodiesEndocrine System DiseasesMalabsorption SyndromesEthylaminesVitiligoStomachGastroscopyFanconi AnemiaPolypsAgammaglobulinemiaGastric FundusEdrophoniumFolic AcidH(+)-K(+)-Exchanging ATPase