What labs should be checked for a patient presenting with hair loss?

From the Guidelines

For a patient presenting with hair loss, I recommend checking a comprehensive panel of laboratory tests, including iron studies, to identify potential underlying causes, despite the lack of strong evidence linking iron deficiency to hair loss in all cases, as seen in studies such as 1 and 1. When evaluating a patient with hair loss, it's essential to consider various potential underlying causes, including nutritional deficiencies, hormonal imbalances, autoimmune disorders, and metabolic abnormalities.

• Key laboratory tests to consider include:
  • A complete blood count (CBC) to assess for anemia
  • Iron studies (serum iron, ferritin, total iron binding capacity) to evaluate iron deficiency, although the evidence for its role in hair loss is not conclusive, as noted in 1 and 1
  • Thyroid function tests (TSH, free T4) to screen for thyroid disorders
  • A comprehensive metabolic panel to assess liver and kidney function
  • Vitamin D levels, zinc levels, and antinuclear antibodies (ANA) if autoimmune conditions are suspected
  • Hormonal levels, including testosterone, DHEAS, and androstenedione, in women to identify hyperandrogenism
  • A morning cortisol test if adrenal disorders are suspected The specific pattern and presentation of hair loss should guide which tests are prioritized, with diffuse hair loss potentially suggesting nutritional or hormonal causes and patchy hair loss indicating autoimmune conditions like alopecia areata, as discussed in 1 and 1.
• It's crucial to note that while some studies suggest a link between iron deficiency and hair loss, particularly in female patients with alopecia areata, as seen in 1 and 1, the evidence is not strong enough to recommend routine iron screening for all patients with hair loss. However, given the potential impact of iron deficiency on hair loss and the relatively low risk of harm from screening, checking iron levels, along with other relevant laboratory tests, is a reasonable approach in the clinical evaluation of hair loss, as supported by the most recent and highest quality studies, such as 1 and 1.

From the Research

Laboratory Tests for Hair Loss

To diagnose the underlying cause of hair loss, several laboratory tests can be ordered. These tests help to identify potential endocrine disorders, nutritional deficiencies, or other underlying conditions that may be contributing to hair loss.

• Complete blood count (CBC) to rule out underlying infections or inflammatory conditions 2
• Ferritin levels to assess iron stores, as iron deficiency anaemia is a common cause of hair loss, particularly in women 3, 2
• Thyroid-stimulating hormone (TSH) levels to evaluate thyroid function, as hypothyroidism or hyperthyroidism can cause hair loss 4, 2
• Vitamin D 25OH levels to assess vitamin D status, as vitamin D deficiency has been linked to hair loss 2
• Hair microscopy to examine the hair shaft and scalp for any abnormalities or damage 3
• Scalp biopsy to confirm a diagnosis of cicatricial alopecia or other scalp conditions 2

Additional Tests

Depending on the patient's medical history and physical examination findings, additional tests may be ordered to rule out other underlying conditions. These may include:

• Hair pull test to assess the amount of hair loss 3
• Trichogram to evaluate the hair growth cycle 4
• Phototrichogram, trichoscan, trichoscopy, or reflectance confocal microscopy to assess hair growth and scalp condition 4
• Tests for autoimmune disorders, such as autoimmune thyroiditis or alopecia areata 4, 5
• Tests for hormonal imbalances, such as polycystic ovary syndrome (PCOS) or hyperprolactinaemia 4