Potential Causes for Iron Deficiency Anemia
Iron deficiency anemia is most commonly caused by gastrointestinal blood loss in men and postmenopausal women, while menstrual blood loss is the predominant cause in premenopausal women, requiring thorough investigation to identify the underlying etiology. 1
Common Causes of Iron Deficiency Anemia
Blood Loss
- Gastrointestinal bleeding: Most common cause in men and postmenopausal women, potentially indicating serious conditions like colorectal or gastric cancer 1
- Menstrual bleeding: Leading cause in premenopausal women 1
- NSAID use: Can cause gastrointestinal erosions and chronic blood loss 1, 2
- Angioectasias: Small-bowel bleeding can lead to chronic iron loss 1
- Portal hypertensive gastropathy: Causes chronic gastrointestinal blood loss in patients with liver disease 1
- Gastric antral vascular ectasia (GAVE): Source of chronic bleeding 1
Malabsorption
- Celiac disease: Impairs duodenal iron absorption 1, 3
- Inflammatory bowel disease: Causes both malabsorption and blood loss 1
- Post-bariatric surgery: Particularly procedures that bypass the duodenum and proximal jejunum 1
- Atrophic gastritis: Reduces acid production needed for iron absorption 2
- H. pylori infection: Interferes with iron absorption 1
Increased Iron Requirements
- Pregnancy: Especially during the third trimester 2
- Childhood/adolescent growth: Rapid growth increases iron requirements 3
Dietary Factors
- Inadequate dietary iron intake: Common in vegetarians and vegans 3, 4
- Poor diet quality: Particularly in elderly and economically disadvantaged populations 1, 4
Prevalence and Risk Factors
- Iron deficiency affects 39% of premenopausal women and 8% of postmenopausal women in the US 1
- 1-4% of men have iron deficiency, with 2% having iron deficiency anemia 1
- During pregnancy, up to 84% of women develop iron deficiency in the third trimester 2
- Prevalence in specific conditions:
Diagnostic Approach
- Serum ferritin: Most powerful test for iron deficiency; levels <45 μg/dL indicate iron deficiency in anemic patients 1
- Important caveat: In inflammatory conditions, ferritin may be elevated (usually <100 μg/dL) despite iron deficiency 1
- Confirmatory tests: Transferrin saturation <20%, soluble transferrin receptor, or reticulocyte hemoglobin equivalent 1, 2
- Microcytosis: Characteristic but may be absent in combined deficiencies 1
Treatment Considerations
Oral Iron Therapy
- First-line therapy for most patients 1, 2
- Standard dose: Ferrous sulfate 325 mg daily (65 mg elemental iron) 5, 2
- Common side effects: Nausea, abdominal pain, constipation 1, 2
Intravenous Iron Therapy
- Indicated for:
Disease-Specific Management
- Inflammatory bowel disease: Treat underlying inflammation and consider IV iron 1
- Portal hypertensive gastropathy: Start with oral iron; consider nonselective β-blockers and IV iron if unresponsive 1
- Celiac disease: Ensure adherence to gluten-free diet to improve iron absorption 1, 3
- Gastric antral vascular ectasia: Consider endoscopic therapy with band ligation or argon plasma coagulation 1, 6
Important Clinical Considerations
- All men and postmenopausal women with iron deficiency anemia should undergo bidirectional GI endoscopy to exclude malignancy 1
- Treat both the underlying cause and the iron deficiency itself for optimal outcomes 1, 4
- Monitor response to therapy; lack of response warrants further investigation 7, 2
- Consider multidisciplinary management including gastroenterologists, hematologists, and nutritionists in complex cases 1