WBR0174
| Author | [[PageAuthor::Rim Halaby, M.D. [1]]] |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Physiology |
| Sub Category | SubCategory::Gastrointestinal |
| Prompt | [[Prompt::A 1-year-old male is bought to the physician's office by his mother for symptoms of fatigue and pica. Upon physical examination you observe skin pallor, pale conjunctivae, and spooning of the finger nails. Following appropriate work-up, you diagnose the child with iron deficiency anemia. The patient is prescribed oral iron supplementation. At which level of the GI tract is iron absorbed?]] |
| Answer A | AnswerA::Duodenum |
| Answer A Explanation | AnswerAExp::The proximal duodenum is the predominant site of iron absorption. |
| Answer B | AnswerB::Stomach |
| Answer B Explanation | AnswerBExp::The stomach is not the site of iron absorption. |
| Answer C | AnswerC::Jejunum |
| Answer C Explanation | AnswerCExp::The jejunum is the site of folate absorption. |
| Answer D | AnswerD::Ileum |
| Answer D Explanation | AnswerDExp::The terminal ileum is the site of vitamin B12 absorption. |
| Answer E | AnswerE::Cecum |
| Answer E Explanation | AnswerEExp::The cecum is not the site of iron absorption. |
| Right Answer | RightAnswer::A |
| Explanation | [[Explanation::The patient requires oral iron supplementation. Iron is absorbed in the duodenum as ferrous (Fe2+) iron. At physiological pH, ferrous iron is readily oxidized into ferric (Fe3+) iron, which is not as readily absorbed by the duodenum as ferrous iron. In vivo, however, the acidity present in the stomach allows the absorption of iron in the form of ferrous iron in the duodenum. The use of proton pump inhibitors that reduce the gastric acidity thus decrease the absorption of iron in the duodenum due to the decreased availability of ferrous iron. Educational Objective: Ferrous iron is absorbed in the GI tract mostly at the level of the duodenum. |
| Approved | Approved::No |
| Keyword | WBRKeyword::iron, WBRKeyword::ferrous, WBRKeyword::ferric, WBRKeyword::state, WBRKeyword::oxidized, WBRKeyword::oxidation, WBRKeyword::pH, WBRKeyword::acid, WBRKeyword::acidity, WBRKeyword::acidic, WBRKeyword::duodenum, WBRKeyword::absorption, WBRKeyword::absorb, WBRKeyword::absorbed |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |