Acquired Hypothyroidism in Children

Introduction to Acquired Hypothyroidism in Children

Acquired hypothyroidism is a condition characterized by insufficient production of thyroid hormones, developing after the neonatal period in previously euthyroid children. It is one of the most common endocrine disorders in pediatrics.

Key points:

  • Most common cause is autoimmune thyroiditis (Hashimoto's thyroiditis)
  • Prevalence increases with age, more common in females
  • Can significantly impact growth, development, and overall health
  • Early diagnosis and treatment are crucial for optimal outcomes

Etiology of Acquired Hypothyroidism in Children

Several factors can lead to the development of acquired hypothyroidism in children:

  1. Autoimmune Thyroiditis:
    • Hashimoto's thyroiditis: Most common cause
    • Associated with other autoimmune conditions (e.g., Type 1 diabetes, celiac disease)
  2. Iatrogenic Causes:
    • Post-surgical: Following total or partial thyroidectomy
    • Post-radiation: After radioactive iodine therapy or external beam radiation to the neck
    • Medication-induced: Lithium, amiodarone, tyrosine kinase inhibitors
  3. Iodine-related:
    • Iodine deficiency (rare in developed countries)
    • Iodine excess (e.g., from iodine-containing medications or supplements)
  4. Infiltrative Disorders:
    • Langerhans cell histiocytosis
    • Cystinosis
    • Sarcoidosis (rare in children)
  5. Central Hypothyroidism:
    • Pituitary or hypothalamic disorders affecting TSH production
  6. Genetic Causes:
    • Mutations in genes involved in thyroid hormone synthesis (rare in acquired cases)

Clinical Manifestations of Acquired Hypothyroidism in Children

The clinical presentation of acquired hypothyroidism in children can be subtle and nonspecific:

  1. Growth and Development:
    • Deceleration of linear growth
    • Delayed bone age
    • Pubertal delay or rarely precocious puberty
  2. Physical Appearance:
    • Weight gain or obesity
    • Coarse, dry hair
    • Dry, cold skin
    • Facial puffiness
    • Goiter (in autoimmune thyroiditis)
  3. Neurological and Cognitive:
    • Fatigue and lethargy
    • Poor school performance
    • Decreased concentration
    • Headaches
  4. Gastrointestinal:
    • Constipation
    • Decreased appetite
  5. Cardiovascular:
    • Bradycardia
    • Mild hypertension
  6. Other Symptoms:
    • Cold intolerance
    • Muscle aches and weakness
    • Menstrual irregularities in adolescent girls

Diagnosis of Acquired Hypothyroidism in Children

Diagnosing acquired hypothyroidism involves a combination of clinical assessment and laboratory tests:

  1. Clinical Evaluation:
    • Detailed history and physical examination
    • Assessment of growth parameters and pubertal status
    • Evaluation for signs and symptoms of hypothyroidism
  2. Laboratory Tests:
    • Thyroid Function Tests:
      • TSH: Elevated in primary hypothyroidism
      • Free T4: Low or low-normal
      • Total T3: Usually less affected in early stages
    • Thyroid Antibodies:
      • Anti-thyroid peroxidase (anti-TPO) antibodies
      • Anti-thyroglobulin (anti-Tg) antibodies
  3. Imaging Studies:
    • Thyroid ultrasound: To assess gland size and echogenicity
    • Thyroid scan (rarely needed): In cases of suspected ectopic thyroid or thyroid dysgenesis
  4. Additional Investigations:
    • Bone age X-ray: Often delayed in longstanding hypothyroidism
    • Lipid profile: May be abnormal in hypothyroidism
    • Screening for associated autoimmune conditions (e.g., celiac disease, Type 1 diabetes)

Treatment of Acquired Hypothyroidism in Children

The primary treatment for acquired hypothyroidism is thyroid hormone replacement therapy:

  1. Medication:
    • Levothyroxine (L-thyroxine) is the treatment of choice
    • Available as tablets, which can be crushed for younger children if necessary
  2. Dosing:
    • Initial dose based on age and body weight:
      • 0-3 months: 10-15 μg/kg/day
      • 3-6 months: 8-10 μg/kg/day
      • 6-12 months: 6-8 μg/kg/day
      • 1-5 years: 5-6 μg/kg/day
      • 6-12 years: 4-5 μg/kg/day
      • >12 years: 2-3 μg/kg/day
    • Dose adjustments made based on clinical response and thyroid function tests
  3. Administration:
    • Given once daily, preferably in the morning
    • Should be taken on an empty stomach, 30-60 minutes before eating
    • Avoid co-administration with iron, calcium, or multivitamins
  4. Treatment Goals:
    • Normalize TSH and Free T4 levels
    • Alleviate symptoms of hypothyroidism
    • Restore normal growth and development
  5. Patient Education:
    • Importance of daily medication adherence
    • Need for regular follow-up and monitoring
    • Potential interactions with other medications and supplements

Monitoring and Follow-up of Acquired Hypothyroidism in Children

Regular monitoring is essential to ensure adequate treatment and optimal outcomes:

  1. Laboratory Monitoring:
    • TSH and Free T4 levels:
      • 4-6 weeks after treatment initiation or dose change
      • Every 3-6 months once stable
      • More frequent monitoring may be needed in infants and young children
    • Goal: TSH within normal range, Free T4 in upper half of normal range
  2. Clinical Monitoring:
    • Growth parameters: Height, weight, and growth velocity
    • Pubertal development
    • Symptom resolution
    • School performance and cognitive function
  3. Dose Adjustments:
    • Based on clinical response and laboratory results
    • May need frequent adjustments during periods of rapid growth
  4. Long-term Follow-up:
    • Annual thyroid function tests once stable
    • Monitoring for potential complications or associated conditions
    • Transition planning for adolescents moving to adult care

Complications and Special Considerations in Pediatric Acquired Hypothyroidism

Several complications and special considerations are important in managing pediatric acquired hypothyroidism:

  1. Growth and Development:
    • Growth failure if untreated or undertreated
    • Delayed puberty
    • Potential for accelerated bone maturation with overtreatment
  2. Cognitive and Academic:
    • Potential for learning difficulties and attention problems
    • Importance of neuropsychological assessment in severe or longstanding cases
  3. Cardiovascular:
    • Risk of dyslipidemia
    • Mild hypertension
    • Pericardial effusion in severe cases
  4. Associated Autoimmune Conditions:
    • Increased risk of other autoimmune disorders (e.g., Type 1 diabetes, celiac disease)
    • Need for periodic screening
  5. Thyroid Nodules and Cancer:
    • Increased risk of thyroid nodules in autoimmune thyroiditis
    • Need for regular thyroid palpation and consideration of ultrasound
  6. Pregnancy Considerations:
    • Importance of optimal thyroid function in adolescent pregnancies
    • Need for dose adjustments during pregnancy
  7. Medication Adherence:
    • Challenges in long-term adherence, especially in adolescents
    • Importance of ongoing education and support


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