67 Thyroid Disorders
67.1 Introduction
The thyroid gland plays a critical role in regulating growth, metabolism, and neurodevelopment in children. Thyroid disorders are among the most common endocrine problems in paediatrics and may present with growth retardation, developmental delay, or changes in metabolic rate.
Because thyroid hormones influence almost every organ system, the clinical manifestations of their dysfunction are diverse and often subtle, especially in infants and children.
This note provides an overview of thyroid physiology, outlines common thyroid disorders in children, and discusses their clinical presentation, investigation, and management.
67.2 Anatomy and Physiology
The thyroid gland is a butterfly-shaped organ located in the anterior neck. It secretes the hormones thyroxine (T4) and triiodothyronine (T3) under the control of thyroid-stimulating hormone (TSH) from the anterior pituitary, which is regulated by thyrotropin-releasing hormone (TRH) from the hypothalamus.
Functions of thyroid hormones:
- Regulation of metabolic rate and energy expenditure.
- Promotion of growth and skeletal maturation.
- Essential for brain development, especially in the first 2–3 years of life.
- Maintenance of cardiovascular, gastrointestinal, and neuromuscular functions.
67.3 Classification of Thyroid Disorders
Thyroid diseases in children may be classified as:
| Category | Examples |
|---|---|
| Functional abnormalities | Hypothyroidism, Hyperthyroidism |
| Structural abnormalities | Goitre, Thyroid nodules, Thyroid carcinoma |
| Inflammatory/autoimmune disorders | Hashimoto’s thyroiditis, Graves’ disease |
| Congenital abnormalities | Thyroid dysgenesis, Dyshormonogenesis, Thyroid hormone resistance |
67.4 Congenital Hypothyroidism
67.4.1 Definition
A condition present at birth due to a deficiency of thyroid hormone production, leading to impaired neurodevelopment and growth if untreated.
67.4.2 Aetiology
- Thyroid dysgenesis (≈85%) — agenesis, ectopia, or hypoplasia.
- Dyshormonogenesis (≈10%) — enzyme defects in hormone synthesis.
- Central hypothyroidism (rare) — pituitary or hypothalamic dysfunction.
- Transient causes — maternal antithyroid drugs, iodine deficiency or excess.
67.4.3 Pathophysiology
Lack of thyroid hormone during early infancy leads to irreversible brain damage and developmental delay. Early detection and treatment are therefore crucial.
67.4.4 Clinical Features
Symptoms are often subtle at birth due to transplacental maternal T4.
Typical features include:
- Prolonged neonatal jaundice
- Feeding difficulties and lethargy
- Large fontanelle, macroglossia, umbilical hernia
- Hypotonia and dry skin
- Later: growth retardation, developmental delay, coarse facial features, hoarse cry.
67.4.5 Diagnosis
- Newborn screening: Elevated TSH, low T4.
- Confirmatory tests: Serum TSH and free T4.
- Imaging: Thyroid ultrasound or radionuclide scan to assess gland structure.
67.4.6 Management
- Levothyroxine: 10–15 µg/kg/day orally, initiated as soon as diagnosis is made (ideally within 2 weeks of birth).
- Monitoring: TSH and free T4 every 2–4 weeks initially, then every 3 months after 6 months of age.
- Long-term care: Normal growth and neurodevelopment if therapy is started early and adherence is maintained.
67.5 Acquired Hypothyroidism
67.5.1 Aetiology
- Autoimmune thyroiditis (Hashimoto’s disease) — the most common cause in older children and adolescents.
- Iodine deficiency or excess.
- Drugs (lithium, amiodarone, antithyroid medications).
- Post-irradiation or post-surgical.
- Pituitary or hypothalamic dysfunction (secondary hypothyroidism).
67.5.2 Clinical Features
- Growth failure and delayed bone age.
- Lethargy, cold intolerance, and constipation.
- Weight gain, dry skin, brittle hair.
- Bradycardia and delayed puberty.
- Diffuse or nodular goitre (in autoimmune thyroiditis).
67.5.3 Investigations
- Serum TSH (usually elevated) and free T4 (low).
- Antithyroid antibodies (anti-TPO, anti-thyroglobulin) are positive in Hashimoto’s disease.
- Thyroid ultrasound — may show heterogeneous echotexture in cases of autoimmune disease.
67.5.4 Management
- Levothyroxine replacement: 2–4 µg/kg/day in children; adjust based on growth and lab monitoring.
- Regular monitoring of growth velocity, TSH, and T4 levels.
- Lifelong therapy in autoimmune cases; temporary therapy in transient hypothyroidism.
67.6 Hyperthyroidism in Children
67.6.1 Overview
Hyperthyroidism results from excessive circulating thyroid hormones, leading to increased metabolic rate and sympathetic overactivity.
It is much less common in children than hypothyroidism, but is most often due to Graves’ disease.
67.6.2 Aetiology
- Graves’ disease (autoimmune) — antibodies stimulate TSH receptors → excess hormone synthesis.
- Toxic multinodular goitre or adenoma.
- Thyroiditis (transient thyrotoxicosis due to gland inflammation).
- Iatrogenic (excessive thyroxine intake).
67.6.3 Clinical Features
- Weight loss despite a good appetite.
- Heat intolerance, sweating, palpitations.
- Tremor, irritability, hyperactivity, poor school performance.
- Tachycardia, goitre, and exophthalmos (Graves’ disease).
- Accelerated bone maturation and growth.
67.6.4 Diagnosis
- Low TSH, elevated T3 and T4.
- Thyroid antibodies: positive TSH receptor antibodies in Graves’ disease.
- Radioiodine uptake: diffuse in Graves’, focal in toxic adenoma, low in thyroiditis.
67.6.5 Management
67.6.5.1 Antithyroid Drugs
- Carbimazole (0.5–1 mg/kg/day) or Methimazole are first-line.
- Treatment is usually continued for 12–24 months, with gradual tapering.
- Monitor for side effects: agranulocytosis, rash, hepatotoxicity.
67.6.5.2 Beta-blockers
- Propranolol (1–2 mg/kg/day) for control of tachycardia, tremor, and anxiety.
67.6.5.3 Definitive Therapy
- Radioiodine ablation (rarely used in children under 10).
- Subtotal thyroidectomy for drug-resistant or relapsed cases.
67.6.5.4 Long-Term Follow-Up
- Regular assessment of growth, heart rate, and thyroid function.
- Watch for iatrogenic hypothyroidism after definitive treatment.
67.7 Autoimmune Thyroiditis (Hashimoto’s Disease)
67.7.1 Pathophysiology
Autoimmune destruction of the thyroid gland mediated by T-lymphocytes and antibodies against thyroid peroxidase (TPO) and thyroglobulin.
It may coexist with other autoimmune disorders (e.g., type 1 diabetes, Addison’s disease).
67.7.2 Clinical Features
- Painless, firm, diffuse goitre.
- Features of hypothyroidism may develop gradually.
- Occasionally presents with transient hyperthyroidism (“Hashitoxicosis”).
67.7.3 Investigations
- Elevated TSH, low or normal T4.
- Positive anti-TPO or anti-thyroglobulin antibodies.
- Ultrasound: heterogeneous echotexture.
67.7.4 Management
- Levothyroxine replacement for hypothyroid patients.
- Observation for euthyroid patients with small goitres.
- Screening for other autoimmune diseases (diabetes, celiac disease).
67.8 Goitre in Children
67.8.1 Definition
An enlarged thyroid gland is visible or palpable in the neck.
67.8.2 Causes
| Category | Examples |
|---|---|
| Physiological | Pubertal growth spurt |
| Iodine deficiency | Endemic goitre |
| Autoimmune | Hashimoto’s, Graves’ |
| Dyshormonogenesis | Genetic enzyme defects |
| Neoplasms | Benign nodules, carcinoma |
67.8.3 Clinical Evaluation
- Size, symmetry, tenderness, and presence of nodules.
- Symptoms of pressure or dysfunction (dysphagia, hoarseness, hypo-/hyperthyroid signs).
67.8.4 Investigations
- Serum TSH and free T4.
- Thyroid antibodies.
- Ultrasound: to distinguish diffuse vs nodular enlargement.
- Fine-needle aspiration cytology (FNAC) for suspicious nodules.
67.8.5 Management
- Treat the underlying cause.
- Iodine supplementation in deficiency areas.
- Levothyroxine suppressive therapy for benign goitres.
- Surgical excision for compressive or suspicious nodules.
67.9 Thyroid Nodules and Cancer
67.9.1 Overview
Thyroid nodules are uncommon in children but carry a higher risk of malignancy (20–25%) than in adults.
67.9.2 Risk Factors
- Prior head and neck irradiation.
- Family history of thyroid cancer (MEN2, familial medullary carcinoma).
- Chronic lymphocytic thyroiditis.
67.9.3 Types
- Papillary carcinoma – most common (≈70–80%).
- Follicular carcinoma – second most common.
- Medullary carcinoma – associated with MEN2 syndromes.
- Anaplastic carcinoma – extremely rare in children.
67.9.4 Clinical Features
- Solitary firm nodule, sometimes fixed to surrounding tissue.
- Cervical lymphadenopathy.
- Hoarseness or dysphagia (advanced disease).
67.9.5 Investigations
- Ultrasound: solid hypoechoic nodule with microcalcifications.
- FNAC: gold standard for cytological diagnosis.
- Thyroid function tests: usually normal.
- Thyroglobulin: tumour marker in differentiated cancers.
67.9.6 Management
- Surgery: near-total or total thyroidectomy.
- Radioiodine ablation for residual tissue or metastases.
- Thyroxine suppression therapy to prevent TSH stimulation.
- Long-term follow-up with thyroglobulin levels and imaging.
67.10 Investigations in Suspected Thyroid Disorders
| Investigation | Purpose |
|---|---|
| Serum TSH and free T4 | Assess functional status |
| Thyroid antibodies | Autoimmune thyroid disease |
| Ultrasound scan | Structure, nodules, cysts |
| Radioiodine uptake scan | Evaluate the function and nodules |
| FNAC | Cytological diagnosis |
| Newborn screening | Early detection of congenital hypothyroidism |
67.11 Key Points in Paediatric Thyroid Disorders
- Early detection and treatment of congenital hypothyroidism are crucial for preventing irreversible brain damage.
- Autoimmune thyroiditis is the most common cause of acquired hypothyroidism in children.
- Graves’ disease is the leading cause of paediatric hyperthyroidism.
- Thyroid nodules in children should be thoroughly evaluated due to a higher risk of malignancy.
- Long-term follow-up with growth and developmental monitoring is essential in all thyroid disorders.
67.12 Summary Table
| Disorder | Key Features | Diagnostic Findings | Main Treatment |
|---|---|---|---|
| Congenital Hypothyroidism | Prolonged jaundice, macroglossia, poor growth | ↑TSH, ↓T4 | Levothyroxine 10–15 µg/kg/day |
| Hashimoto’s Thyroiditis | Goitre, growth failure, and autoimmune markers | ↑TSH, anti-TPO + | Levothyroxine |
| Graves’ Disease | Weight loss, tachycardia, exophthalmos | ↓TSH, ↑T3/T4, TRAb + | Carbimazole ± β-blockers |
| Goitre (Iodine Deficiency) | Diffuse neck swelling | Normal or ↑TSH | Iodine or thyroxine |
| Thyroid Cancer | Solitary firm nodule | FNAC positive | Surgery ± radioiodine |
67.13 Suggested Reading
- Nelson Textbook of Paediatrics, 22nd Edition.
- Sperling MA. Pediatric Endocrinology, 5th Edition.
- WHO. Guidelines for the Management of Thyroid Disorders in Children.
- ESPE (European Society for Paediatric Endocrinology) Clinical Practice Recommendations, 2023.