What are the diagnostic criteria and treatment options for androgenic (male/female pattern) alopecia in women?

Diagnosis of Androgenetic Alopecia in Women

Androgenetic alopecia in women is primarily a clinical diagnosis based on characteristic patterns of hair thinning (diffuse, male-pattern, or Christmas-tree pattern) combined with trichoscopy showing hair shaft diameter diversity, without requiring laboratory testing in most cases. 1, 2, 3

Clinical Presentation and Patterns

Women with androgenetic alopecia present with three distinct patterns that differ from male presentation 2:

• Diffuse pattern: Generalized thinning across the central scalp with preservation of the frontal hairline 2
• Male-pattern: Bitemporal recession and vertex thinning similar to men 2
• Christmas-tree pattern: Widening of the central part with a distinctive shape 2

The condition affects up to 50% of women by age 50, making it the most common cause of hair loss in women 4, 3, 5

Diagnostic Tools and Methods

Trichoscopy (Dermoscopy of the Scalp)

Trichoscopy is superior to trichogram for diagnosing female androgenetic alopecia and should be the primary diagnostic tool. 6

• Hair shaft diameter diversity >20% is considered diagnostic, though trichoscopy has 100% diagnostic yield irrespective of the 20% cut-off 6
• Trichoscopy is particularly valuable in early cases where trichogram may miss the diagnosis 6
• This non-invasive method allows for staging disease severity and monitoring treatment response 3

Trichogram

• Useful to assess progression of hair loss but less sensitive than trichoscopy 4, 6
• In one study, trichogram diagnosed only 62% of cases versus 72% for trichoscopy (using 20% cut-off) 6

Scalp Biopsy

• Diagnostic but usually not required since clinical diagnosis combined with trichoscopy is sufficient 4
• Reserved for uncertain cases or when differential diagnosis is challenging 1

Laboratory Testing Strategy

Laboratory testing is NOT necessary for typical presentations of androgenetic alopecia but should be performed when signs of hyperandrogenism are present. 1, 4

When to Order Laboratory Tests

Order the following panel when women present with signs of androgen excess (acne, hirsutism, irregular periods) 1, 2:

• Total testosterone or bioavailable/free testosterone 1
• Sex hormone binding globulin (SHBG) 1
• Dehydroepiandrosterone sulfate (DHEA-S) to evaluate for adrenal disorders 2
• Prolactin if hyperprolactinemia suspected 1
• Two-hour oral glucose tolerance test if diabetes or insulin resistance suspected (to evaluate for polycystic ovary syndrome) 1
• Fasting lipid panel 1

Additional Testing to Consider

• Thyroid stimulating hormone (TSH) to rule out thyroid disease, which commonly coexists with hair loss 1, 2
• Serum ferritin as iron deficiency is the most common nutritional deficiency worldwide and causes chronic diffuse telogen hair loss 1
• Vitamin D levels since 70% of women with hair loss have deficiency (<20 ng/mL) versus 25% of controls 1
• Zinc levels as they tend to be lower in patients with alopecia 1
• Complete blood count 2

Differential Diagnosis Considerations

When diagnosis is uncertain, consider 1:

• Alopecia areata: Look for patchy loss, exclamation mark hairs, yellow dots on dermoscopy 1
• Telogen effluvium: Stress-induced diffuse shedding with identifiable trigger 1
• Trichotillomania: Incomplete hair loss with firmly anchored broken hairs 1
• Tinea capitis: Requires fungal culture for confirmation 1
• Systemic lupus erythematosus: Consider serology when suspected 1
• Thyroid disease: Check TSH 1

Common Diagnostic Pitfalls to Avoid

• Do not order excessive laboratory tests when the clinical presentation is typical - androgenetic alopecia is diagnosed clinically in most cases 1, 4
• Do not overlook trichoscopy as a non-invasive diagnostic tool that provides more information than trichogram 1, 6
• Do not miss hyperandrogenism - investigate for polycystic ovarian disease or late-onset congenital adrenal hyperplasia when signs of androgen excess are present 4
• Do not ignore the psychological impact - assess for anxiety and depression as hair loss causes significant stress and psychological problems in women 1, 2

Diagnostic Algorithm

1. Obtain detailed history focusing on pattern of hair loss, family history, menstrual irregularities, signs of hyperandrogenism 4, 2

2. Perform trichoscopy looking for hair shaft diameter diversity >20% 6

3. If signs of hyperandrogenism present (acne, hirsutism, irregular periods): Order testosterone, SHBG, DHEA-S, prolactin, glucose tolerance test 1, 2

4. If no hyperandrogenism: Consider only TSH and ferritin to rule out common comorbidities 1, 2

5. Reserve scalp biopsy for atypical presentations or diagnostic uncertainty 4