Anemia, PerniciousIntrinsic FactorAchlorhydriaAnemiaSchilling TestVitamin B 12Anemia, MacrocyticVitamin B 12 DeficiencyCobalt IsotopesAnemia, MegaloblasticHydroxocobalaminGastrinsPostgastrectomy SyndromesParietal Cells, GastricMigraine DisordersGastric JuiceAnemia, HypochromicGastritis, AtrophicGastric MucosaMigraine without AuraGastritisAnemia, AplasticTension-Type HeadacheCarcinoid TumorEnterochromaffin CellsAnemia, HemolyticZollinger-Ellison SyndromeFolic Acid DeficiencyCobalt RadioisotopesAutoimmune DiseasesAutoantibodiesEndocrine System DiseasesMalabsorption SyndromesEthylaminesVitiligoStomachGastroscopyFanconi AnemiaPolypsAgammaglobulinemiaGastric FundusEdrophoniumFolic AcidHeadacheH(+)-K(+)-Exchanging ATPase