Iron Deficiency Anemia with Functional Iron Deficiency in a 59-Year-Old Man

This patient has functional iron deficiency (iron-deficient erythropoiesis despite adequate iron stores) requiring intravenous iron therapy, mandatory gastrointestinal evaluation to exclude malignancy, and discontinuation of chronic calcium carbonate use that impairs iron absorption.

Laboratory Interpretation

Your patient's iron studies reveal a critical pattern:

Transferrin saturation (TSAT) = 5% (calculated as [19/382] × 100) confirms severe iron-deficient erythropoiesis, well below the 16-20% diagnostic threshold for absolute iron deficiency 1
Ferritin = 11 ng/mL indicates depleted iron stores, as values <15 ng/mL definitively diagnose absolute iron deficiency regardless of inflammatory status 2
Elevated TIBC = 382 mg/dL and elevated transferrin = 330 mg/dL reflect the body's compensatory attempt to maximize iron-binding capacity when iron is severely depleted 2
Elevated UIBC = 363 mg/dL confirms the vast majority of transferrin binding sites are vacant and desperately seeking iron 1

This constellation—TSAT <20%, ferritin <30 ng/mL, elevated TIBC—defines absolute iron deficiency requiring aggressive repletion 3, 1.

Immediate Treatment: Intravenous Iron

Oral iron has already failed in this patient because chronic calcium carbonate (Tums) use directly impairs intestinal iron absorption by precipitating iron in the gut lumen 2. The American Gastroenterological Association recommends immediate intravenous iron for patients with:

Oral iron intolerance or malabsorption 4
Severe iron depletion (ferritin <30 ng/mL) 4
Ongoing blood loss exceeding oral absorption capacity 2

Specific IV Iron Protocol

Choose one of these FDA-approved formulations 4:

Ferric carboxymaltose (preferred): 1000 mg IV over 15 minutes as a single dose, with treatment-related adverse events in only 2.7% of patients 4
Iron isomaltoside: 1000 mg IV without test dose 4
Low-molecular-weight iron dextran: Can give >1000 mg single dose but requires mandatory test dose due to FDA-boxed warning for anaphylaxis 4

Expected response: Hemoglobin should rise 1-2 g/dL within 4-8 weeks, and ferritin should exceed 100 ng/mL 4, 2.

Monitoring After IV Iron

Do not recheck iron parameters within 4 weeks of infusion—circulating iron produces falsely elevated results 1, 4
Repeat CBC, ferritin, and TSAT at 8-10 weeks post-infusion 4, 2
Target TSAT ≥20% and ferritin ≥30 ng/mL (≥100 ng/mL if chronic inflammation present) 1, 2

Mandatory Gastrointestinal Evaluation

All men with iron deficiency anemia require bidirectional endoscopy to exclude gastrointestinal malignancy 3, 2. The British Society of Gastroenterology states this is non-negotiable in men and postmenopausal women 3.

Required Workup

Upper endoscopy (EGD) with duodenal biopsies to evaluate for:
- Gastric cancer 3
- Celiac disease (present in up to 4% of IDA cases) 4
- Peptic ulcer disease 3
- Angiodysplasia 3
Colonoscopy (preferred over CT colonography or barium enema) to detect:
- Colon cancer 3
- Adenomatous polyps 3
- Angiodysplasia 3
- NSAID-induced damage 3
Celiac serology (tissue transglutaminase antibodies) if not already performed 4, 2
Helicobacter pylori testing (already negative in your patient, which is appropriate) 3

Critical Pitfall to Avoid

Do not accept findings of esophagitis, gastritis, or peptic ulcer disease as the sole explanation for IDA until colonoscopy is completed 3. These upper GI lesions rarely cause sufficient blood loss to produce severe iron deficiency without an additional lower GI source 3.

Address the PSA Elevation

The mildly elevated PSA (4.3 ng/mL) in a 59-year-old warrants age-appropriate prostate cancer screening, but this is not the cause of his anemia 1. Coordinate with urology for:

Digital rectal examination
Consider prostate MRI or biopsy based on shared decision-making
Urinalysis to exclude hematuria (which would prompt renal imaging) 3

Discontinue Chronic Calcium Carbonate Use

Calcium carbonate (Tums) directly impairs iron absorption by precipitating iron salts in the alkaline environment it creates 2. For his heartburn:

Switch to a proton pump inhibitor (PPI) or H2-receptor antagonist
However, recognize that PPIs also reduce iron absorption by decreasing gastric acid needed to solubilize ferrous iron 2
Given his severe iron deficiency, IV iron bypasses this absorption problem entirely 1

Levetiracetam and Hematologic Effects

The FDA label for levetiracetam documents minor but statistically significant decreases in hemoglobin (mean 0.09 g/dL) and hematocrit (mean 0.38%) in controlled trials 5. However:

These changes are clinically insignificant and do not explain his severe anemia (Hgb 8.9 g/dL) 5
Levetiracetam does not cause iron deficiency 6, 7
Do not discontinue levetiracetam for seizure control—his anemia has a clear gastrointestinal/nutritional etiology 5

Long-Term Management

After IV iron repletion and treatment of any identified GI pathology 4:

Monitor hemoglobin and ferritin every 3 months for 1 year, then annually 4
If iron deficiency recurs despite treating the underlying cause, consider intermittent IV iron supplementation 4
Avoid continuing iron supplementation once ferritin normalizes—this is potentially harmful 4
Address dietary iron intake with nutritional consultation 3

Why Oral Iron Will Fail in This Patient

Only 21% of patients who fail initial oral iron respond to continued oral therapy, whereas 65% respond when switched to IV iron 2. Your patient has multiple factors predicting oral iron failure:

Chronic calcium carbonate use blocking absorption 2
Possible ongoing GI blood loss (yet to be identified) 2
Severe baseline depletion (ferritin 11 ng/mL) requiring rapid repletion 4

Bottom line: IV iron is not just preferred—it is the only rational choice given his clinical scenario 4, 2.

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