Soluble Transferrin Receptor (sTfR)
Soluble transferrin receptor is the truncated extracellular domain of cellular TfR1 cleaved into serum, directly proportional to cellular iron demand.
Standard vs. Optimal Reference Rangesmg/L
Standard reference intervals represent the statistical 95% distribution of unselected commercial populations. Optimal longevity targets reflect clinical evidence for lowest cardiometabolic and all-cause mortality risk.
Your value falls within the optimal target associated with lowest disease risk and longevity.
0.9 - 2.3 mg/L
General reference distribution across unselected commercial populations.
1.0 - 1.8 mg/L
Concentration target associated with minimal all-cause cardiometabolic mortality.
Molecular Mechanism & Clinical Purpose
When erythroblasts experience intracellular iron deprivation, TfR1 expression increases exponentially. Because sTfR is unaffected by acute-phase inflammation, it reliably diagnoses iron deficiency in patients with elevated ferritin.
Differential Diagnosis
Elevated Levels (sTfR High)
- •True iron deficiency anemia (even in the presence of inflammatory disorders)
- •Hemolytic anemia / High erythroid marrow hyperplasia
Low Levels (sTfR Low)
- •Aplastic anemia / Marrow hypoplasia
- •Iron overload states
Technical Reference & Deep Dive
Biochemistry & Enzymatic Pathways
Longevity Risk Architecture & Epidemiology
Pre-Analytical Caveats & Diagnostic Workup
Pre-Analytical Considerations:
Venipuncture must be performed in the morning (between 7:00 AM and 10:00 AM) due to pronounced diurnal variation in circulating iron levels. A 12-hour overnight fast is required; avoid oral iron supplements for at least 24 to 48 hours prior to testing. Ferritin is an acute-phase reactant; measure concurrent hs-CRP to rule out falsely elevated ferritin from systemic inflammation or acute infection.
Reflexive Testing Protocol:
- Complete Iron Panel (Serum Iron, Total Iron-Binding Capacity, Ferritin, Transferrin Saturation Percentage)
- Soluble Transferrin Receptor (sTfR) and sTfR-Ferritin Index to differentiate iron deficiency anemia from anemia of chronic disease
- HFE Gene Mutation Analysis (C282Y, H63D) to screen for hereditary hemochromatosis in cases of persistent transferrin supersaturation
- High-sensitivity C-Reactive Protein (hs-CRP) and Erythrocyte Sedimentation Rate (ESR) to evaluate inflammatory status
- Upper and lower endoscopy (EGD and Colonoscopy) to rule out occult gastrointestinal blood loss in unexplained iron deficiency
Clinical Citations & Primary Literature (1)
- [1]Soluble Transferrin Receptor in Differentiating Anemia of Chronic Disease from Iron Deficiency - American Journal of Hematology (2022). PMID: 34988735
Associated Longevity Guides & Clinical Calculators
Medicine 3.0Explore comprehensive evidence-based clinical protocols, testing costs, and algorithmic calculators that incorporate Soluble Transferrin Receptor (sTfR) into overall healthspan optimization.