Serum Ferritin Levels: A Clinical Guide in Patients With Hair Loss

Clinical Utility of Serum Ferritin

Low Ferritin and Iron Deficiency—Although bone marrow biopsy with iron staining remains the gold standard for diagnosis of iron deficiency, serum ferritin is a much more accessible and less invasive tool for evaluation of iron status. A serum ferritin level below 12 μg/L is highly specific for iron depletion,²² with a higher cutoff recommended in clinical practice to improve diagnostic sensitivity.^23,24 Conditions independent of iron deficiency that may reduce serum ferritin include hypothyroidism and ascorbate deficiency, though neither condition has been reported to interfere with appropriate diagnosis of iron deficiency.²⁵ Guyatt et al²⁶ conducted a systematic review of laboratory tests used in the diagnosis of iron deficiency anemia and identified 55 studies suitable for inclusion. Based on an area under the receiver operating characteristic curve (AUROC) of 0.95, serum ferritin values were superior to transferrin saturation (AUROC, 0.74), red cell protoporphyrin (AUROC, 0.77), red cell volume distribution width (AUROC, 0.62), and mean cell volume (AUROC, 0.76) for diagnosis of IDA, verified by histologic examination of aspirated bone marrow.²⁶ The likelihood ratio of iron deficiency begins to decrease for serum ferritin values of 40 μg/L or greater. For patients with inflammatory conditions—patients with concomitant chronic renal failure, inflammatory disease, infection, rheumatoid arthritis, liver disease, inflammatory bowel disease, and malignancy—the likelihood of iron deficiency begins to decrease at serum ferritin levels of 70 μg/L or greater.²⁶ Similarly, the World Health Organization recommends that in adults with infection or inflammation, serum ferritin levels lower than 70 μg/L may be used to indicate iron deficiency.²⁴ A serum ferritin level of 41 μg/L or lower was found to have a sensitivity and specificity of 98% for discriminating between iron-deficiency anemia and anemia of chronic disease (diagnosed based on bone marrow biopsy with iron staining), with an AUROC of 0.98.²⁷ As such, we recommend using a serum ferritin level of 40 μg/L or lower in patients who are otherwise healthy as an indicator of iron deficiency.

The threshold for iron supplementation may vary based on age, sex, and race. In women, ferritin levels increase during menopause and peak after menopause; ferritin levels are higher in men than in women.^28-30 A multisite longitudinal cohort study of 70 women in the United States found that the mean (SD) ferritin valuewas 69.5 (81.7) μg/L premenopause and 128.8 (125.7) μg/L postmenopause (P<.01).³¹ A separate longitudinal survey study of 8564 patients in China found that the mean (SE) ferritin value was 201.55 (3.60) μg/L for men and 80.46 (1.64) μg/L for women (P<.0001).³² Analysis of serum ferritin levels of 3554 male patients from the third National Health and Nutrition Examination Survey demonstrated that patients who self-reported as non-Hispanic Black (n=1616) had significantly higher serum ferritin levels than non-Hispanic White patients (n=1938)(serum ferritin difference of 37.1 μg/L)(P<.0001).³³ The British Society for Haematology guidelines recommend that the threshold of serum ferritin for diagnosing iron deficiency should take into account age-, sex-, and race-based differences.³⁴ Ferritin and Hair—Cutaneous manifestations of iron deficiency include koilonychia, glossitis, pruritus, angular cheilitis, and telogen effluvium (TE).¹ A case-control study of 30 females aged 15 to 45 years demonstrated that the mean (SD) ferritin level was significantly lower in patients with TE than those with no hair loss (16.3 [12.6] ng/mL vs 60.3 [50.1] ng/mL; P<.0001). Using a threshold of 30 μg/L or lower, the investigators found that the odds ratio for TE was 21.0 (95% CI, 4.2-105.0) in patients with low serum ferritin.³⁵

Another retrospective review of 54 patients with diffuse hair loss and 55 controls compared serum vitamin B₁₂, folate, thyroid-stimulating hormone, zinc, ferritin, and 25-hydroxy vitamin D levels between the 2 groups.³⁶ Exclusion criteria were clinical diagnoses of female pattern hair loss (androgenetic alopecia), pregnancy, menopause, metabolic and endocrine disorders, hormone replacement therapy, chemotherapy, immunosuppressive therapy, vitamin and mineral supplementation, scarring alopecia, eating disorders, and restrictive diets. Compared with controls, patients with diffuse nonscarring hair loss were found to have significantly lower ferritin (mean [SD], 14.72 [10.70] ng/mL vs 25.30 [14.41] ng/mL; P<.001) and 25-hydroxy vitamin D levels (mean [SD], 14.03 [8.09] ng/mL vs 17.01 [8.59] ng/mL; P=.01).³⁶

In contrast, a separate case-control study of 381 cases and 76 controls found no increase in the rate of iron deficiency—defined as ferritin ≤15 μg/L or ≤40 μg/L—among women with female pattern hair loss or chronic TE vs controls.³⁷ Taken together, these studies suggest that iron status may play a role in TE, a process that may result from nutritional deficiency, trauma, or physical or psychological stress³⁸; however, there is insufficient evidence to suggest that low iron status impacts androgenetic alopecia, in which its multifactorial pathogenesis implicates genetic and hormonal factors.³⁹ More research is needed to clarify the potential associations between iron deficiency and types of hair loss. Additionally, it is unclear whether iron supplementation improves hair growth parameters such as density and caliber.⁴⁰

Low serum ferritin (<40 μg/L) with concurrent symptoms of iron deficiency, including fatigue, pallor, dyspnea on exertion, or hair loss, should prompt treatment with supplemental iron.^41-43 Generally, ferrous (Fe2⁺) salts are preferred to ferric (Fe3⁺) salts, as the former is more readily absorbed through the duodenal mucosa⁴⁴ and is the more common formulation in commercially available supplements in the United States.⁴⁵ Oral supplementation with ferrous sulfate 325 mg (65 mg elemental iron) tablets is the first-line therapy for iron deficiency anemia.¹ Alternatively, ferrous gluconate 324 mg (38 mg elemental iron) over-the-counter and its liquid form has demonstrated superior absorption compared to ferrous sulfate tablets in a clinical study with peritoneal dialysis patients.^1,46 One study suggested that oral iron 40 to 80 mg should be taken every other day to increase absorption.⁴⁷ Due to improved bioavailability, intravenous iron may be utilized in patients with malabsorption, renal failure, or intolerance to oral iron (including those with gastric ulcers or active inflammatory bowel disease), with the formulation chosen based on underlying comorbidities and potential risks.^1,48 The theoretical risk for potentiating bacterial growth by increasing the amount of unbound iron in the blood raises concerns of iron supplementation in patients with infection or sepsis. Although far from definitive, existing data suggest that risk for infection is greater with intravenous iron supplementation and should be carefully considered prior to use.^49,50Elevated Ferritin—Elevated ferritin may be difficult to interpret given the multitude of conditions that can cause it.^23,51,52 Elevated serum ferritin can be broadly characterized by increased synthesis due to iron overload, increased synthesis due to inflammation, or increased ferritin release from cellular damage.³⁴ Further complicating interpretation is the potential diurnal fluctuations in serum iron levels dependent on dietary intake and timing of laboratory evaluation, choice of assay, differences in reference standards, and variations in calibration procedures that can lead to analytic variability in the measurement of ferritin.^23,53,54

Among healthy patients, serum ferritin is directly proportional to iron status.^9,51 A study utilizing weekly phlebotomy of 22 healthy participants to measure serum ferritin and calculate mobilizable storage iron found a strong positive correlation between the 2 variables (r=0.83, P<.001), with each 1-μg/L increase of serum ferritin corresponding to approximately an 8-mg increase of storage iron; the initial serum ferritin values ranged from 2 to 83 μg/L in females and 36 to 224 μg/L in males.⁵⁵ The correlation of ferritin with iron status also was supported by the significant correlation between the number of transfusions received in patients with transfusion-related iron overload and serum ferritin levels (r=0.89, P<.001), with an average increase of 60 μg/L per transfusion.⁵¹

Clinical guidelines on the interpretation of serum ferritin levels by Cullis et al³⁴ recommend a normal upper limit of 200 μg/L for healthy females and 300 μg/L for healthy males. Outside of clinical syndromes associated with iron overload, Lee and Means⁵⁶ found that serum ferritin of 1000 μg/L or higher was a nonspecific marker of disease, including infection and/or neoplastic disorders. We have adapted these guidelines to propose a workflow for evaluation of serum ferritin levels (Figure). In patients with inflammatory conditions or those affected by metabolic syndrome, elevated serum ferritin does not correlate with body iron status.^57,58 It is believed that inflammatory cytokines, including tumor necrosis factor α and IL-1α, can upregulate ferritin synthesis independent of cellular iron stores.^15,16 Several studies have examined the relationship between insulin resistance and/or metabolic syndrome with serum ferritin levels.^31,32 Han et al³² found that elevated serum ferritin was significantly associated with higher risk for metabolic syndrome in men (P<.0001) but not in women.

Proposed workflow for investigation of serum ferritin (SF) levels in patients without known iron overload.^24,26,34,56 ALT indicates alanine aminotransferase; AST, aspartate aminotransferase; CBC, complete blood cell count; LFT, liver function tests; MRI, magnetic resonance imaging; TSAT, transferrin saturation.