What are the possible causes of severe iron deficiency in a 17-year-old female with a ferritin level indicating severe iron deficiency?

Severe Iron Deficiency in a 17-Year-Old Female: Possible Causes

In a 17-year-old female with severe iron deficiency, the most likely causes are heavy menstrual bleeding (affecting 10% of menstruating women), inadequate dietary iron intake (only 25% of adolescent girls meet recommended intake), and rapid pubertal growth demands—with gastrointestinal pathology being less common in this age group but still requiring investigation if other causes are excluded. 1

Primary Causes in Adolescent Females

Menstrual Blood Loss

• Heavy menstrual bleeding (≥80 mL/month) is the single most important risk factor for iron deficiency in adolescent girls and women of childbearing age, affecting approximately 10% of this population 1
• Intrauterine device use increases menstrual blood loss and iron deficiency risk 1
• Oral contraceptive use is protective and decreases iron deficiency risk 1

Inadequate Dietary Iron Intake

• Only one-fourth of adolescent girls aged 12-18 years meet the recommended dietary allowance for iron through diet alone 1
• The recommended daily allowance for girls 14-18 years old is 15 mg/day 1
• Restrictive diets pose escalating risk in this order: no red meat < vegetarian < vegan, as heme iron from meat is better absorbed than plant-based non-heme iron 1, 2
• Plant iron sources contain nutrients that reduce non-heme iron absorption 1

Increased Physiologic Demands

• During adolescence (ages 12-18 years), iron requirements increase substantially due to rapid pubertal growth, creating a critical vulnerability period 1
• Among girls, menstruation compounds this increased demand throughout childbearing years, unlike boys where risk subsides after peak pubertal growth 1

Secondary Causes Requiring Investigation

Gastrointestinal Blood Loss

• While less common in adolescents than adults, occult gastrointestinal bleeding must be excluded when iron deficiency is unexplained or severe 1, 3, 4
• NSAID use can cause occult GI blood loss 1
• In the absence of overt blood loss or obvious cause, upper gastrointestinal endoscopy with small bowel biopsy and colonoscopy should be performed to exclude malignancy 1

Malabsorption Disorders

• All young women with low ferritin must be screened for celiac disease with tissue transglutaminase antibodies (tTG Ab), as this is a common and treatable cause 2, 4, 5
• Atrophic gastritis impairs iron absorption 4
• Inflammatory bowel disease causes both malabsorption and chronic blood loss in 13-90% of affected patients 3, 4
• Previous gastrectomy or gastric bypass surgery creates anatomical changes limiting iron absorption 1, 3

Athletic Activity

• Female athletes have iron deficiency prevalence estimates ranging from 15-35%, with some studies suggesting rates >50% 1
• Sports involving high amounts of running cause repetitive ground strikes leading to increased iron loss 1
• Endurance training causes antioxidant depletion and erythrocyte damage 1

Critical Diagnostic Considerations

Interpreting Ferritin Levels

• Ferritin <15 μg/L has 99% specificity for absolute iron deficiency and confirms the diagnosis definitively 2, 3
• Ferritin <35 μg/L indicates depleted iron stores warranting treatment, even without anemia 2
• Ferritin is an acute-phase reactant that rises with infection, inflammation, or tissue damage, potentially masking true iron deficiency 1, 2, 3
• If inflammatory markers (CRP/ESR) are elevated, use transferrin saturation <16-20% as an additional marker 2, 3, 4

Common Pitfalls to Avoid

• Do not assume dietary insufficiency alone without investigating menstrual patterns—heavy menstrual bleeding is the leading cause in this demographic 1
• Do not overlook celiac disease screening—this is mandatory in all young women with iron deficiency 2
• Do not dismiss symptoms when hemoglobin is normal—iron deficiency without anemia still causes significant fatigue, lethargy, and reduced exercise tolerance 2, 4
• In adolescent females at high risk, screen twice yearly for iron deficiency rather than waiting for symptoms to develop 3

Less Common but Important Causes

Other Medical Conditions

• Inflammatory or bleeding disorders affect iron status 1
• Certain medications (anticonvulsants, sulfasalazine, methotrexate) may affect iron metabolism indirectly 3
• Parasitic infections, particularly hookworm, though more common in developing regions 1

Socioeconomic Factors

• Limited access to food due to low family income, migrant status, or refugee status increases risk 1, 5
• Low socioeconomic status is an independent risk factor for iron deficiency anemia 5