What investigations should be done for female pattern hair loss?

Diagnostic Investigations for Female Pattern Hair Loss

The diagnostic approach for female pattern hair loss (FPHL) should include laboratory testing for ferritin, vitamin D, zinc, folate, and thyroid function to identify underlying nutritional deficiencies or hormonal imbalances that may contribute to hair loss. 1

Initial Laboratory Evaluation

• Serum ferritin levels should be assessed in all women with FPHL, as iron deficiency is a common contributor to hair loss, particularly in women 1, 2
• Thyroid function tests (TSH and free T4) are recommended to rule out thyroid dysfunction, which can cause or exacerbate hair loss 1, 3
• Vitamin D levels should be checked, as deficiency has been associated with various forms of hair loss including FPHL 1
• Zinc levels assessment is important as zinc deficiency can contribute to hair loss 1
• Folate levels should be evaluated, as folate deficiency may play a role in hair loss 1, 3

Additional Testing for Suspected Androgen Excess

• Total testosterone or bioavailable/free testosterone levels should be measured in women with signs of androgen excess (acne, hirsutism, irregular periods) 1, 4
• Sex hormone binding globulin (SHBG) levels should be checked in women with suspected hyperandrogenism 1
• Consider testing for polycystic ovary syndrome (PCOS) in women with signs of androgen excess and FPHL 1, 4
• Prolactin levels should be assessed if hyperprolactinemia is suspected 1

Diagnostic Tools Beyond Laboratory Testing

• Dermoscopy is a valuable non-invasive diagnostic tool that can help differentiate FPHL from other causes of hair loss 1, 5
• Clinical photography should be used to document baseline hair density and monitor treatment response 6
• Hair wash test can help quantify the degree of hair shedding 7
• Trichoscan or trichogram may be used for more objective assessment of hair density and growth 7

When to Consider Skin Biopsy

• Skin biopsy should be considered in cases with atypical presentation or when the diagnosis remains uncertain despite clinical evaluation and laboratory testing 1
• Biopsy is particularly helpful to differentiate FPHL from scarring alopecia or diffuse alopecia areata 1, 5

Common Pitfalls to Avoid

• Failing to check ferritin levels - the threshold for adequate hair growth (≥60 ng/mL) is higher than the lower limit of normal for anemia prevention 2
• Overlooking the psychological impact of FPHL, which may warrant assessment for anxiety and depression 1, 6
• Ordering excessive laboratory tests when the diagnosis is clinically evident 1
• Delaying treatment initiation - early diagnosis and treatment are more effective at arresting progression than stimulating regrowth 6

Interpretation of Results

• Iron deficiency for hair growth should be defined as serum ferritin <60 ng/mL, which is higher than the threshold for anemia 2
• The corresponding hemoglobin level for optimal hair growth is ≥13.0 g/dL 2
• Normal androgen levels do not rule out FPHL, as isolated FPHL without hyperandrogenism is common 4

By following this comprehensive diagnostic approach, clinicians can identify underlying factors contributing to FPHL and develop targeted treatment strategies to address both the hair loss and any associated conditions.