What vitamin and mineral deficiencies, and other lab investigations, should be studied in a patient, particularly a woman with a history of thyroid disorders, autoimmune diseases, or recent significant weight loss, presenting with telogen effluvium?

Laboratory Investigations for Telogen Effluvium

Essential First-Line Laboratory Tests

All patients presenting with telogen effluvium should have serum ferritin, vitamin D, thyroid function tests (TSH and free T4), vitamin B12, and zinc levels checked, as these represent the most clinically relevant deficiencies associated with hair loss. 1, 2, 3

Iron Studies

• Serum ferritin is the single most important test, as iron deficiency is the most common nutritional deficiency worldwide and a primary cause of chronic diffuse telogen hair loss 1, 3
• Ferritin deficiency occurs in 46.5% of women with telogen effluvium, making it the most frequently identified abnormality 4
• Iron deficiency anemia (low hemoglobin with low ferritin) is present in approximately 6.2% of patients 3
• Complete blood count should be obtained to identify anemia, though isolated ferritin measurement is more sensitive for detecting iron deficiency before anemia develops 3, 4

Vitamin D

• Vitamin D deficiency (<20 ng/mL) is present in 70-72% of patients with hair loss, representing the most prevalent vitamin deficiency 1, 2, 3
• Lower vitamin D levels correlate inversely with disease severity in alopecia areata and other forms of hair loss 1
• The vitamin D receptor plays a critical role in hair follicle cycling, making this measurement clinically relevant beyond general health 1

Thyroid Function

• TSH and free T4 should be checked in all patients, as thyroid dysfunction occurs in approximately 4.6% of telogen effluvium cases 3
• Both hypothyroidism and hyperthyroidism can trigger telogen effluvium 1, 2
• If biochemical hypothyroidism is confirmed (high TSH, low free T4), thyroid peroxidase (TPO) antibody testing is warranted to identify autoimmune thyroid disease 1

Vitamin B12 and Folate

• Vitamin B12 deficiency occurs in 5.8-30.7% of patients with telogen effluvium, depending on the population studied 3, 4
• Folate deficiency is less common (0.6-4.4%) but should still be assessed 3, 4
• These deficiencies are particularly relevant in patients with malabsorption, strict dietary restrictions, or recent significant weight loss 5

Zinc

• Serum zinc levels tend to be lower in patients with telogen effluvium, occurring in approximately 2.1% when using standard reference ranges 3
• A 2024 study found zinc levels were significantly lower in chronic telogen effluvium patients compared to controls, with diagnostic performance for predicting the condition 6
• Zinc serves as a cofactor for multiple enzymes involved in hair follicle function 1, 2

Additional Investigations in Specific Clinical Contexts

For Women with Signs of Androgen Excess

When patients present with acne, hirsutism, irregular periods, or other signs of hyperandrogenism alongside hair loss:

• Total testosterone or bioavailable/free testosterone levels 2
• Sex hormone binding globulin (SHBG) 2
• Consider screening for polycystic ovary syndrome (PCOS) with two-hour oral glucose tolerance test if diabetes or insulin resistance is suspected 2
• Prolactin level if hyperprolactinemia is suspected 2
• Fasting lipid and lipoprotein levels to evaluate for dyslipidemia 2

For Patients with Autoimmune Disease History

• Antinuclear antibody (ANA) titers to screen for systemic lupus erythematosus, which can cause both scarring and non-scarring alopecia 1, 3
• Consider additional autoimmune serologies if clinical suspicion exists, as approximately 20% of alopecia areata patients have other autoimmune conditions 1

Less Commonly Indicated Tests

• Copper levels: The Cu/Zn ratio may have diagnostic value, with one 2024 study finding it to be a significant predictor of chronic telogen effluvium 6
• Selenium levels: Found to be significantly higher in chronic telogen effluvium patients in one study, though clinical significance remains unclear 6
• Biotin levels: A 2020 study found no significant difference in serum biotin levels between telogen effluvium patients and controls, suggesting routine biotin testing is not warranted 7

Critical Pitfalls to Avoid

Do Not Over-Test

• Avoid ordering excessive laboratory tests when the clinical diagnosis is evident through history and dermoscopic examination 1, 2
• Biotin supplementation should be avoided or discontinued before testing, as it interferes with diagnostic test results, particularly thyroid function tests 2

Do Not Under-Investigate in High-Risk Populations

• Women with thyroid disorders require comprehensive thyroid panel (TSH, free T4, TPO antibodies if hypothyroid) 1, 4
• Patients with autoimmune disease history warrant broader autoimmune screening including ANA titers 1, 3
• Recent significant weight loss mandates nutritional assessment including ferritin, vitamin B12, folate, vitamin D, and zinc, as malnutrition occurs in multiple micronutrients simultaneously 5

Consider Malabsorption Syndromes

• Small bowel biopsies should be considered during upper endoscopy if gastrointestinal symptoms are present, as 2-3% of patients with iron deficiency have celiac disease 5
• Patients with inflammatory bowel disease are at particularly high risk for multiple vitamin and mineral deficiencies (vitamin D, iron, vitamin B12, zinc, copper, fat-soluble vitamins, folic acid) 5

Practical Clinical Algorithm

Step 1: Obtain baseline essential tests in ALL patients:

• Serum ferritin
• Vitamin D (25-hydroxyvitamin D)
• TSH and free T4
• Vitamin B12
• Zinc
• Complete blood count 1, 2, 3

Step 2: Add targeted tests based on clinical context:

• Signs of androgen excess → testosterone, SHBG, consider PCOS screening 2
• Autoimmune disease history → ANA titers 1, 3
• Gastrointestinal symptoms or malabsorption → folate, consider celiac screening 5

Step 3: Correct identified deficiencies:

• Vitamin D supplementation if <20 ng/mL 1, 2
• Iron replacement if ferritin is low (most frequently prescribed treatment at 37.5% of cases) 3
• Zinc supplementation if serum levels are low 1, 2
• Vitamin B12 replacement if deficient 3, 4

Step 4: If all tests are normal and hair loss persists, consider:

• Dermoscopic examination to differentiate telogen effluvium from other causes 1
• Detailed medication history (chemotherapy, anticoagulants, beta-blockers) 1
• Assessment for psychological stressors, as emotional distress can trigger telogen effluvium and may warrant referral for anxiety/depression 1, 2