What is the appropriate management for a 76-year-old female patient with iron deficiency anemia, subclinical hypothyroidism, and impaired renal function, as indicated by her recent lab work?

Management of Iron Deficiency Anemia with Impaired Renal Function in a 76-Year-Old Female

This patient requires oral iron supplementation (ferrous sulfate 200mg three times daily) to correct her iron deficiency anemia and replenish body stores, along with gastrointestinal investigation to identify the underlying cause of blood loss, given her age and confirmed iron deficiency. 1

Confirming Iron Deficiency

The laboratory findings confirm iron deficiency anemia:

• Hemoglobin 11.1 g/dL is below the WHO threshold of 12 g/dL for women, meeting criteria for anemia 1
• Ferritin 69 ng/mL with iron saturation 20% indicates true iron deficiency. While ferritin <15 μg/L is highly specific (specificity 0.99), values up to 45 μg/L warrant investigation, and transferrin saturation <20% confirms inadequate iron availability 1
• Normocytic anemia (MCV 97 fL) is consistent with early iron deficiency or mixed etiology, as microcytosis develops later in the disease course 1

Mandatory Gastrointestinal Investigation

At age 76, this patient requires bidirectional endoscopy (gastroscopy with duodenal biopsy and colonoscopy) to exclude gastrointestinal malignancy and other pathology. 1

Key considerations:

• IDA in older adults has high yield for significant pathology, including malignancy, making investigation essential regardless of symptoms 1
• Gastroscopy with small bowel biopsy screens for celiac disease (found in 3-5% of IDA cases) and upper GI sources of bleeding 1
• Colonoscopy or CT colonography evaluates the lower GI tract; CT colonography is reasonable if colonoscopy poses excessive risk given comorbidities 1
• Dual pathology is more common in elderly patients, strengthening the case for complete bidirectional evaluation 1

Iron Replacement Therapy

Initiate ferrous sulfate 200mg three times daily immediately while arranging investigations: 1

• Expected hemoglobin rise of 2 g/dL within 3-4 weeks confirms adequate response and supports the diagnosis 1
• Continue iron for 3 months after hemoglobin normalization to replenish body stores 1, 2
• Intravenous iron should be considered if oral iron is not tolerated after trial of at least two different oral preparations, or if rapid repletion is needed 1, 2
• Ascorbic acid enhances absorption and should be considered if response is suboptimal 1

Addressing Chronic Kidney Disease

The GFR of 68 mL/min/1.73m² indicates Stage 2 CKD, which contributes to anemia but does not fully explain it: 1

• CKD becomes a major cause of anemia when GFR <30 mL/min/1.73m²; at GFR 68, iron deficiency is the primary driver 1
• Functional iron deficiency can occur in CKD due to inflammation and hepcidin upregulation, but this patient's ferritin 69 ng/mL and saturation 20% indicate absolute iron deficiency requiring investigation 1
• The algorithm from heart failure guidelines suggests that with ferritin <100 ng/mL and GFR <60 mL/min, anemia is partly secondary to CKD, but iron deficiency must still be corrected 1

Thyroid Function Assessment

TSH 1.45 and free thyroxine 1.34 are within normal range, excluding thyroid dysfunction as a contributor: 1, 3, 4

• Thyroid dysfunction evaluation is recommended in anemia workup, but this patient's normal thyroid function eliminates this as a cause 1
• Subclinical hypothyroidism (elevated TSH with normal T4) is associated with anemia in 39% of cases, but is not present here 3
• Overt hyperthyroidism has the strongest association with anemia (14.6% prevalence), but subclinical thyroid dysfunction does not significantly increase anemia risk 4

Follow-Up Strategy

After completing investigations and initiating iron therapy: 1

• Monitor hemoglobin and MCV at 3-4 weeks to confirm 2 g/dL rise
• Check hemoglobin every 3 months for one year, then annually
• Further investigation is warranted only if hemoglobin cannot be maintained with iron supplementation, suggesting ongoing blood loss, malabsorption, or incorrect diagnosis 1

Critical Pitfalls to Avoid

• Do not delay GI investigation based on age or comorbidity without careful risk-benefit discussion with the patient and family 1
• Failure to respond to oral iron may indicate continued blood loss, poor compliance, malabsorption, or need for parenteral iron—not necessarily treatment failure 1, 2
• Do not attribute anemia solely to CKD at this GFR level without excluding iron deficiency and GI pathology 1
• Ferritin can be falsely elevated by inflammation; transferrin saturation <20% confirms true iron deficiency even with "normal" ferritin 1