What are the normal serum iron levels for adolescents?

Normal Iron Laboratory Values for Adolescents

For adolescents, normal serum ferritin levels are approximately 30 μg/L, with transferrin saturation of at least 16% considered normal. 1

Iron Parameters in Adolescents

Iron status assessment in adolescents requires understanding of their unique physiological needs during this period of rapid growth and development.

Key Normal Values:

• Serum Ferritin:

  • Average: ~30 μg/L 1
  • Values <15 μg/L confirm iron deficiency 2

• Transferrin Saturation:

  • Normal: ≥16% 1, 3
  • In adolescents, values <16% should be interpreted cautiously and only considered indicative of iron deficiency when accompanied by anemia and low mean corpuscular volume 3

• Soluble Transferrin Receptor:

  • Normal range: 0.9-2.4 mg/L
  • Values >2.4 mg/L indicate subclinical iron deficiency 4

Physiological Considerations in Adolescents

Adolescence is characterized by significant changes in iron homeostasis due to:

1. Rapid Growth: Adolescents experience a growth velocity greater than at any postnatal age since infancy 1

   • Boys achieve peak height velocity of 9.5 cm/year at ~13.5 years
   • Girls achieve peak height velocity of 8.3 cm/year at ~11.5 years

2. Blood Volume Expansion:

   • Increases from ~2600 mL (75 mL/kg) in an 11-year-old to ~4500 mL (70 mL/kg) in a 17-year-old
   • Requires approximately 1000 mg additional iron dedicated to erythropoiesis 1

3. Gender Differences:

   • Female adolescents have higher iron requirements (0.35 mg/kg) than males (0.2 mg/kg) due to menstrual blood loss 1
   • WHO defines anemia in females 12-15 years as Hb <12.0 g/dL 2

4. Hormonal Changes:

   • Hepcidin levels decrease during adolescence in response to estrogen and testosterone production
   • This regulatory mechanism adapts to increased iron demands during puberty 1

Clinical Implications

Iron stores relatively decrease during adolescence as genital stages progress, evidenced by:

• Decreasing serum ferritin levels
• Increasing ratio of soluble transferrin receptor to ferritin 1

When assessing iron status in adolescents, consider:

1. The prevalence of subclinical iron deficiency is approximately 10% in adolescent populations 4
2. Growth and physical activity do not significantly affect iron status measurements 4
3. Serum ferritin is the most specific indicator of depleted iron stores, especially when used with other tests 1

Pitfalls in Interpretation

1. Inflammation Effects: Serum ferritin is an acute-phase reactant; infection, inflammation, or tissue damage can elevate levels independent of iron status 1, 5

2. Age-Specific Considerations: Children and adolescents between 0.5-12 years have significantly lower serum iron concentration and transferrin saturation than adults 3

3. Test Limitations: For transferrin saturation <16%, additional parameters should be assessed before diagnosing iron deficiency in adolescents 3

By understanding these normal values and their context, clinicians can better identify and address iron deficiency in the adolescent population, which is crucial for optimal growth, development, and cognitive function.