What labs should be ordered for a child with hair loss?

Laboratory Evaluation for Children with Hair Loss

Thyroid function tests (TSH and free T4) should be the initial laboratory evaluation for all children with hair loss, followed by iron studies (ferritin), vitamin D levels, and zinc levels to identify treatable underlying causes.

Initial Laboratory Workup

First-Line Tests

• Thyroid function tests

  • TSH and free T4 1, 2
  • Hypothyroidism can present with hair loss, weight gain, fatigue, and cold intolerance 1
  • Even without classic signs of thyroid disease, thyroid function testing is reasonable in children with hair loss 1

• Iron studies

  • Serum ferritin 1, 2
  • Low iron stores can contribute to hair loss even without overt anemia

• Zinc levels 1, 2

  • Clinical features of zinc deficiency include alopecia, skin rash, growth retardation, and impaired immune function
  • Plasma zinc should be measured in the morning (around 8 am) for accurate results

• Vitamin D levels 2

  • Often associated with hair loss, particularly in alopecia areata

Additional Testing Based on Clinical Presentation

For Patchy Hair Loss (Suspected Alopecia Areata)

• Thyroid antibodies (TPO antibody) 1
  • Autoimmune thyroid disease is associated with alopecia areata
  • Particularly important if thyroid function tests show abnormalities

For Diffuse Hair Loss with Systemic Symptoms

• Complete blood count (CBC)

  • To evaluate for underlying anemia or infection

• Inflammatory markers (CRP)

  • Particularly if systemic inflammation is suspected
  • Helps interpret zinc levels, as inflammation affects plasma zinc 1

For Suspected Endocrine Causes

• Morning cortisol or ACTH stimulation test 1
  • If adrenal insufficiency is suspected
  • Particularly important if both adrenal insufficiency and hypothyroidism are present, as steroids should be started before thyroid hormone to avoid adrenal crisis

Special Considerations

For Children with Developmental Delays or Dysmorphic Features

• Genetic testing 1
  • Microarray testing as first-line chromosome study
  • Consider testing for fragile X syndrome in both boys and girls with motor delays
  • Routine chromosome testing for suspected Down syndrome, Turner syndrome, or Klinefelter syndrome

For Suspected Medication-Induced Hair Loss

• No specific laboratory tests required
• Careful medication history is essential, particularly for chemotherapy, endocrine therapy, or other medications known to cause hair loss 1

Interpretation of Results

• Zinc levels: Values <0.4 mmol/L (<32 μg/L) should prompt zinc supplementation 1

  • Always interpret with CRP and albumin levels
  • Plasma zinc decreases significantly when CRP exceeds 20 mg/L

• Thyroid function: Interpret minor abnormalities cautiously 3

  • Slightly abnormal thyroid tests often do not represent true thyroid disease
  • Consider repeat testing in 4-6 weeks before initiating treatment

Clinical Pitfalls to Avoid

1. Overreliance on laboratory testing

   • Not all hair loss requires extensive laboratory evaluation
   • For limited patchy alopecia areata with short duration (<1 year), observation may be appropriate as spontaneous remission occurs in up to 80% of cases 1

2. Failure to consider psychological impact

   • Hair loss can be psychologically devastating for children
   • Consider referral to a pediatric clinical psychologist if significant behavioral changes are observed 1

3. Missing non-medical causes of hair loss

   • Traumatic alopecia from tight hairstyles or traction
   • Trichotillomania (compulsive hair pulling)

4. Treating laboratory values without clinical correlation

   • Minor laboratory abnormalities may not be clinically significant
   • Treatment should be guided by both laboratory results and clinical presentation

By following this systematic laboratory evaluation approach, clinicians can identify treatable causes of hair loss in children while avoiding unnecessary testing and interventions.