Overview
Definition:
Acquired hypothyroidism in pediatrics refers to the development of insufficient thyroid hormone production after birth, often due to autoimmune destruction of the thyroid gland (Hashimoto's thyroiditis) or other acquired causes
It leads to a systemic metabolic slowdown.
Epidemiology:
Hashimoto's thyroiditis is the most common cause of acquired hypothyroidism in children and adolescents in iodine-sufficient regions
Prevalence increases with age, and it is more common in girls
Genetic predisposition and other autoimmune conditions are associated.
Clinical Significance:
Untreated acquired hypothyroidism in children can have profound effects on growth, neurodevelopment, metabolism, and overall well-being
Early diagnosis and appropriate management are crucial to prevent long-term sequelae and ensure normal development
It is a common topic in DNB and NEET SS exams.
Clinical Presentation
Symptoms:
Gradual onset of symptoms
Poor growth or deceleration of growth velocity
Fatigue and lethargy
Cold intolerance
Constipation
Dry skin and hair, hair loss
Delayed puberty
Goiter may be present
Intellectual and developmental delay in severe, untreated cases.
Signs:
Slowed growth parameters
Delayed bone age
Delayed dentition
Pale, cool, dry skin
Puffy face, periorbital edema
Goiter (often diffuse, firm, nontender)
Bradycardia
Deep tendon reflexes with prolonged relaxation phase
Hoarse voice.
Diagnostic Criteria:
Diagnosis is based on biochemical evidence of hypothyroidism (elevated TSH, low fT4) confirmed by repeat testing
Identification of thyroid autoantibodies (anti-TPO, anti-Tg) supports an autoimmune etiology like Hashimoto's
Clinical suspicion and physical findings are key.
Diagnostic Approach
History Taking:
Detailed birth history (neonatal screening for congenital hypothyroidism)
Developmental milestones
Growth charts review
Onset and progression of symptoms
Family history of thyroid disease or autoimmune disorders
Presence of other autoimmune diseases.
Physical Examination:
Assess growth parameters (height, weight, head circumference)
Examine skin, hair, nails
Palpate thyroid gland for size, consistency, nodules
Auscultate for cardiac murmurs
Evaluate for signs of myxedema
Assess neurological development and reflexes.
Investigations:
Initial test: Thyroid Stimulating Hormone (TSH)
If TSH is elevated, measure free Thyroxine (fT4)
If fT4 is low, hypothyroidism is confirmed
Thyroid autoantibodies: Anti-thyroid peroxidase (anti-TPO) antibodies and anti-thyroglobulin (anti-Tg) antibodies
Ultrasound of thyroid if goiter is present
Assess bone age via wrist X-ray if growth is affected.
Differential Diagnosis:
Congenital hypothyroidism (if diagnosis is delayed)
Transient hypothyroidism (e.g., after certain medications, pituitary dysfunction)
Iodine deficiency or excess
Central hypothyroidism (secondary/tertiary)
Goitrogens
Non-thyroidal illness.
Management
Initial Management:
Confirmation of diagnosis with repeat thyroid function tests (TSH, fT4)
Initiation of thyroid hormone replacement therapy with levothyroxine (LT4).
Medical Management:
Levothyroxine (LT4) is the drug of choice
Dosing is crucial and age/weight-dependent
Initial dose: 10-15 mcg/kg/day
Divided into a single morning dose
Adjust dose based on TSH and fT4 levels, typically aiming for TSH in the lower half of the pediatric reference range
Monitor TSH and fT4 every 3-6 months until stable, then annually
Long-term therapy is usually lifelong.
Surgical Management:
Surgery is rarely indicated for acquired hypothyroidism itself
It might be considered for large, symptomatic goiters causing compressive symptoms or for suspicion of malignancy, which is uncommon in pediatric Hashimoto's.
Supportive Care:
Education for parents and child regarding lifelong treatment adherence
Monitoring for growth and development
Nutritional assessment
Addressing psychosocial aspects related to chronic illness.
Age Specific Dosing
Infants 0 6 Months:
Initial dose: 10-15 mcg/kg/day
Monitor TSH weekly initially, then monthly
Dose adjustments based on TSH and clinical status
Critical for neurodevelopment.
Infants 6 12 Months:
Initial dose: 8-10 mcg/kg/day
Monitor TSH every 1-2 months
Dose adjustments are frequent due to rapid growth.
Children 1 5 Years:
Initial dose: 5-7 mcg/kg/day
Monitor TSH every 3-6 months
Dose adjustments based on growth and TSH levels.
Children 5 12 Years:
Initial dose: 3-5 mcg/kg/day
Monitor TSH every 3-6 months
Dose adjustments based on growth and TSH levels.
Adolescents 12 Years:
Initial dose: 2-3 mcg/kg/day
Monitor TSH every 3-6 months
Dose adjustments based on growth, puberty, and TSH levels
Requirements may increase during puberty.
Complications
Early Complications:
Myxedema coma (rare, life-threatening)
Worsening symptoms if treatment is delayed or inadequate
Poor school performance and concentration.
Late Complications:
Impaired growth and delayed puberty if not treated adequately
Long-term effects on cognitive function if diagnosis and treatment are significantly delayed
Increased risk of other autoimmune disorders.
Prevention Strategies:
Early screening in high-risk populations
Prompt investigation of suggestive symptoms
Consistent adherence to treatment regimens
Regular monitoring of thyroid function tests and growth.
Prognosis
Factors Affecting Prognosis:
Age at diagnosis and initiation of treatment
Severity of hypothyroidism at presentation
Adherence to therapy
Presence of other autoimmune conditions.
Outcomes:
With early diagnosis and consistent treatment, prognosis is excellent
Children can achieve normal growth, development, and pubertal maturation
Quality of life is generally good
Long-term monitoring is essential.
Follow Up:
Lifelong monitoring is typically required
Annual follow-up is recommended to assess adherence, monitor thyroid function (TSH, fT4), evaluate growth, and check for development of other autoimmune conditions
Dose adjustments may be needed during periods of rapid growth, puberty, or illness.
Key Points
Exam Focus:
Hashimoto's thyroiditis is the most common cause of acquired hypothyroidism in children
Key investigations are TSH, fT4, and anti-TPO antibodies
Levothyroxine dosing is weight-based and requires careful titration based on TSH levels
Dosing in infants is critical for neurodevelopment.
Clinical Pearls:
Always plot growth parameters on standard charts to detect growth deceleration
Consider thyroid disease in children with unexplained fatigue, constipation, or developmental delay
Start levothyroxine at a lower dose in infants and titrate slowly
TSH is the most sensitive marker for hypothyroidism and adequate treatment.
Common Mistakes:
Starting levothyroxine at too high a dose in infants, leading to thyrotoxicosis symptoms
Insufficient monitoring leading to sub-optimal treatment and poor growth
Misinterpreting transient hypothyroidism as permanent
Not considering other autoimmune associations.