Unit Converter
Transferrin
(Primary Iron Transport Protein - Central Marker in Iron Deficiency, Anemia Evaluation & Nutritional Status)
Synonyms
- Transferrin
- Serum transferrin
- Siderophilin
- Beta-1 metal-binding globulin
- Total Iron-Binding Globulin (TBG, older term - NOT Thyroxine-Binding Globulin)
- TIBC precursor (transferrin × 25 ≈ TIBC)
Units of Measurement
- µmol/L
- g/L
- mg/dL
- mg/100 mL
- mg%
- mg/mL
Unit Conversions
Molecular Weight of Transferrin ≈ 79,500 Da (≈ 79.5 kDa)
µmol/L ↔ g/L
1 µmol/L=0.0795 g/L1\ \text{µmol/L} = 0.0795\ \text{g/L}1 µmol/L=0.0795 g/L 1 g/L=12.6 µmol/L1\ \text{g/L} = 12.6\ \text{µmol/L}1 g/L=12.6 µmol/L
mg/dL → g/L
1 mg/dL=0.01 g/L1\ \text{mg/dL} = 0.01\ \text{g/L}1 mg/dL=0.01 g/L
mg/100 mL = mg% = mg/dL
mg/mL → g/L
1 mg/mL=1 g/L1\ \text{mg/mL} = 1\ \text{g/L}1 mg/mL=1 g/L
Description
Transferrin is the major iron-transport glycoprotein synthesized in the liver.
Its functions include:
- Binding ferric iron (Fe³⁺) with high affinity
- Transporting iron to bone marrow for erythropoiesis
- Delivering iron to tissues
- Maintaining safe iron levels by preventing free-iron toxicity
Transferrin concentration increases in iron deficiency and decreases in chronic inflammatory states, making it a critical component of iron studies.
Physiological Role
1. Iron Transport
Each molecule carries two Fe³⁺ ions.
2. Iron Homeostasis
Prevents free-iron catalyzed oxidative damage.
3. Nutritional Marker
Reflects liver protein synthesis.
4. Component of Iron Studies Panel
Transferrin is directly linked to:
- Total Iron-Binding Capacity (TIBC)
- Transferrin saturation (TS%)
- Serum iron
Clinical Significance
HIGH TRANSFERRIN
→ The body is trying to “bind more iron”-seen in low iron states.
Major Causes
1. Iron Deficiency
Early increase before anemia appears.
2. Pregnancy
Estrogen → ↑ transferrin production.
3. Oral Contraceptives / Estrogen Therapy
4. Acute Blood Loss
Reactive increase.
5. Polycythemia Vera
Pattern in Iron Deficiency
- Serum iron ↓
- Transferrin ↑
- TIBC ↑
- Transferrin saturation ↓ (<15%)
LOW TRANSFERRIN
1. Chronic Inflammatory Disease
Negative acute-phase reactant.
- RA
- Chronic infections
- Malignancy
2. Liver Disease
Reduced hepatic synthesis.
3. Nephrotic Syndrome
Loss of transferrin in urine.
4. Malnutrition / Protein-Energy Deficiency
5. Hemochromatosis
Body suppresses transferrin as iron overload increases.
6. Burns, Severe Trauma, Critical Illness
7. Inherited Atransferrinemia
Very rare — severe iron overload and anemia.
Reference Intervals
(Tietz 8E + Mayo + ARUP + WHO Fe Deficiency Guidelines)
Serum Transferrin
- 2.0 – 3.6 g/L
or - 200 – 360 mg/dL
or - 25 – 45 µmol/L
Interpretive Clues
| Condition | Transferrin Level |
| Iron deficiency | ↑ high |
| Anemia of chronic disease | ↓ low |
| Liver cirrhosis | ↓ low |
| Pregnancy/OCPs | ↑ |
| Hemochromatosis | ↓ |
Diagnostic Uses
1. Iron Deficiency Workup
Early and sensitive marker.
2. Differentiating Anemias
- ↑ Transferrin → iron deficiency
- ↓ Transferrin → chronic inflammation or iron overload
3. Iron Overload Disorders
Low transferrin is typical in:
- Hemochromatosis
- Hemosiderosis
4. Liver Function Evaluation
Low transferrin → impaired hepatic synthetic function.
5. Nutritional Status
Decreases with protein-energy malnutrition.
6. Monitoring in Pregnancy & Estrogen Therapy
Analytical Notes
- Measured by immunoassay (nephelometry or turbidimetry).
- Hemolysis has minimal effect.
- Severe inflammation lowers transferrin (negative APR).
- Transferrin saturation should be calculated with simultaneous serum iron.
Clinical Pearls
- Transferrin is inverse of ferritin in iron deficiency:
- Ferritin ↓
- Transferrin ↑
- Ferritin ↓
- Low transferrin + low iron → think anemia of chronic disease, NOT iron deficiency.
- High transferrin saturation (>45%) strongly suggests hemochromatosis.
- Pregnancy raises transferrin, but ferritin remains most reliable for iron stores.
- TIBC is simply transferrin × 25 when expressed in µmol/L.
Interesting Fact
Transferrin not only carries iron - it also plays roles in viral entry inhibition, immune function, and antioxidant defense, making it far more than just a transport protein.
References
- Tietz Clinical Chemistry & Molecular Diagnostics, 8th Edition - Iron & Binding Proteins
- WHO Iron Deficiency Diagnosis Guidelines
- Mayo Clinic Laboratories - Transferrin
- ARUP Consult - Iron Studies
- BSH Guidelines - Iron Deficiency & Anaemia
- NIH / MedlinePlus - Transferrin Test