What are the causes and management of madarosis (loss of eyebrows or eyelashes) in pregnancy with normal thyroid function tests?

Madarosis in Pregnancy with Normal Thyroid Function

In pregnant women with madarosis and normal thyroid function tests, the most likely causes are nutritional deficiencies (particularly iron and iodine), autoimmune conditions (alopecia areata, frontal fibrosing alopecia), dermatological disorders, or infections—not thyroid disease.

Primary Differential Diagnosis

Nutritional Deficiencies

• Iron deficiency is a critical consideration in pregnancy and can cause hair loss including madarosis, even when thyroid function appears normal 1
• Iodine deficiency during pregnancy is common and affects thyroid metabolism; pregnant women have sharply increased iodine needs that are frequently not covered by food sources 1
• Iron deficiency specifically impairs thyroid metabolism at the cellular level, potentially causing hair loss despite normal TSH levels 1

Autoimmune Hair Loss Disorders

• Alopecia areata presents with characteristic trichoscopic findings including exclamation mark hairs (30% of cases), tapered hairs (14%), broken hairs (36%), and black dots (26%) 2
• Frontal fibrosing alopecia shows dystrophic hairs (28%), whitish areas (32%), and eyebrow regrowth in distinct directions (32%) on dermoscopy 2
• Both conditions commonly affect eyebrows and can occur during pregnancy 2

Dermatological and Infectious Causes

• Blepharitis from various causes including fungal infections (dermatophytes like Microsporum species) can present with madarosis 3
• Eczematous or seborrheic blepharitis may progress to eyelash loss if untreated 3
• Look for erythematous squamous lesions, ocular pruritus, and chronic mixed blepharitis 3

Diagnostic Approach

Clinical Examination Priorities

• Assess for scarring vs. non-scarring madarosis, as this determines potential for regrowth 4
• Perform dermoscopy/trichoscopy of the eyebrow and eyelash area to identify specific patterns:
  • Empty follicular openings (yellow dots) suggest active hair loss 2
  • Exclamation mark hairs indicate alopecia areata 2
  • Dystrophic hairs and white areas suggest frontal fibrosing alopecia 2

Laboratory Evaluation

• Check iron studies (ferritin, serum iron, TIBC) as iron deficiency is common in pregnancy and causes hair loss 1
• Measure 24-hour urinary iodine excretion (deficiency <100 mcg/24hr) or serum iodine (normal 40-100 mcg/L) 1
• Consider mycological examination if blepharitis is present with scales or resistant to initial treatment 3

Additional Considerations

• Evaluate for other body/scalp hair loss to determine if madarosis is isolated or part of systemic alopecia 4
• Screen for signs of systemic diseases: lupus, scleroderma, HIV/AIDS, though these are less common 4

Management Strategy

Nutritional Supplementation

• Iodine supplementation: 150 mcg daily is mandatory for all pregnant women in iodine-deficient areas 1
• Iron supplementation: Treat documented iron deficiency aggressively as it impairs thyroid hormone metabolism at the tissue level 1

Condition-Specific Treatment

• For alopecia areata: Consider topical or intralesional corticosteroids (discuss risks/benefits in pregnancy)
• For blepharitis: Initiate appropriate antifungal treatment (systemic and topical) if fungal etiology confirmed 3
• For frontal fibrosing alopecia: Early dermatology referral as this is typically scarring and requires prompt intervention 2

Critical Pitfalls to Avoid

• Do not assume normal TSH excludes thyroid-related hair loss: Iron and iodine deficiency can cause madarosis through impaired peripheral thyroid hormone metabolism despite normal TSH 1
• Do not delay microbiological examination in atypical or treatment-resistant blepharitis, as fungal infections require specific antifungal therapy 3
• Do not overlook nutritional screening: Pregnancy dramatically increases micronutrient demands, and deficiencies are common even in developed countries 1