What causes hair loss?

Common Causes of Hair Loss

Hair loss can be caused by a variety of factors including genetic predisposition, hormonal imbalances, autoimmune conditions, systemic diseases, medications, environmental factors, and physical stress to the hair follicles. 1, 2

Major Categories of Hair Loss

1. Androgenetic Alopecia (Pattern Hair Loss)

• Most common form of hair loss 2
• Characterized by:
  • Progressive miniaturization of hair follicles
  • Conversion from long growth (anagen) and short rest (telogen) cycles to short growth and long rest cycles 3
  • Genetically determined sensitivity to androgens
  • Affects up to 50% of white males by age 50 3
• Treatment:
  • First-line: Topical minoxidil 5% twice daily 1, 2
  • For men: Oral finasteride 2, 3
  • For women with hormonal abnormalities: Oral antiandrogens (spironolactone, cyproterone acetate) 1

2. Autoimmune Hair Loss

• Alopecia Areata:

  • Characterized by patchy, non-scarring hair loss
  • Exclamation mark hairs at expanding margins 4
  • 34-50% of patients recover within 1 year, but most experience multiple episodes 4
  • Poor prognosis indicators: childhood onset, ophiasis pattern, progression to alopecia totalis/universalis 4
  • Treatment: Intralesional corticosteroids for limited patches, topical corticosteroids, or oral immunosuppressants 4, 1, 2

• Autoimmune Thyroiditis:

  • Can cause hair loss even with normal TSH levels 1
  • Requires complete hormonal analysis (T3, T4 free) 1
  • Treatment: Optimize thyroid function 1

3. Telogen Effluvium (Diffuse Hair Loss)

• Triggered by:
  • Stress
  • Severe illness
  • Fever
  • Hemorrhage
  • Childbirth
  • Nutritional deficiencies 5
• Usually self-limited once underlying cause is addressed 2
• Characterized by diffuse shedding of telogen hairs

4. Medication-Induced Hair Loss

• Mechanisms:
  • Anagen arrest (abrupt cessation of hair growth)
  • Telogen effluvium (premature shifting of hairs into resting phase)
  • Accentuation of androgenetic alopecia 5
• Common culprits: chemotherapy drugs, anticoagulants, antithyroid medications, retinoids, beta-blockers

5. Nutritional and Metabolic Causes

• Iron deficiency (check ferritin levels) 1
• Vitamin D deficiency 1
• Protein malnutrition
• Zinc deficiency
• Treatment: Appropriate supplementation of deficient nutrients 1

6. Physical/Environmental Factors

• Traction alopecia (from tight hairstyles)
• Heat damage from styling tools
• Chemical damage from hair treatments
• Solar radiation exposure 6
• Treatment: Reduce physical stress to hair follicles 2

7. Fungal Infections

• Tinea capitis (scalp ringworm)
• Characterized by inflammation, scaling
• Treatment: Oral antifungals 2

Diagnostic Approach

1. Visual examination:

   • Pattern of hair loss (diffuse, patterned, focal)
   • Presence of inflammation or scaling
   • Hair shaft abnormalities

2. Specialized tests:

   • Trichoscopy to examine miniaturization patterns 1
   • Hair pull test (positive if >6 hairs extracted) 1
   • Dermoscopy to identify specific features (yellow dots, black dots, exclamation mark hairs) 1

3. Laboratory testing when indicated:

   • Complete blood count
   • Ferritin levels
   • Thyroid function tests (TSH, T3, T4)
   • Vitamin D levels 1

Treatment Considerations

• Document baseline with photographs and hair density measurements 1
• Regular monitoring every 3-6 months to assess response 1
• Consider psychological impact - hair loss is associated with anxiety, depression, and reduced quality of life 2
• Additional options for resistant cases:
  • Low-level laser therapy
  • Platelet-rich plasma therapy
  • Hair transplantation for stable disease 1

Common Pitfalls to Avoid

1. Attributing all hair loss to androgenetic alopecia without investigating other causes 7
2. Failing to check for nutritional deficiencies, especially iron and vitamin D
3. Not considering medication side effects as potential causes
4. Overlooking autoimmune conditions, particularly thyroid disorders
5. Ignoring the psychological impact of hair loss
6. Setting unrealistic expectations for treatment outcomes

Remember that prognosis varies significantly by condition - telogen effluvium typically resolves with removal of the trigger, while alopecia areata has variable recovery rates based on severity (68% recovery with <25% hair loss, but only 8% recovery with >50% hair loss) 1.