A 28-year-old woman with heavy menstrual bleeding presents with fatigue. Labs show serum iron 25 mcg/dL, TIBC 480 mcg/dL, and ferritin 8 ng/mL. Bone marrow iron stain shows absent storage iron. What is the sequential pattern of iron study abnormalities that occurs as iron deficiency progresses from iron depletion to established iron deficiency anemia?

• A Serum iron falls first, then TIBC rises, then ferritin falls, then hemoglobin falls
• B TIBC rises first, then ferritin falls, then serum iron falls, then hemoglobin falls
• C Ferritin falls first, then serum iron falls and TIBC rises, then hemoglobin falls ✓
• D Hemoglobin falls first, then ferritin falls, then TIBC rises, then serum iron falls

Explanation

Iron deficiency progresses in stages. First, iron stores deplete and serum ferritin falls (below 12-15 ng/mL) while other parameters remain normal. Next, serum iron falls and TIBC rises as transferrin synthesis increases. Finally, when stores are exhausted and supply cannot meet erythropoietic demands, microcytic hypochromic anemia develops. This sequence is well established in hematology texts. Option A is wrong because ferritin, not serum iron, falls earliest. Option B reverses the order of TIBC rise relative to ferritin fall. Option D is wrong because anemia is the last manifestation, not the first.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

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Written and medically reviewed by the StethoPrep medical team.