Makindo Medical Notes

Related Subjects: |Thyrotoxicosis and Hyperthyroidism |Thyroid Storm - Thyrotoxic crisis |Graves Disease (Thyrotoxicosis) |Amiodarone and Thyroid disease |Thyroid Surgery (Thyroidectomy) |Hypothyroidism |Hashimoto's thyroiditis |DeQuervain's thyroiditis |Subacute Thyroiditis |Thyroid nodule |Congenital Hypothyroidism |Thyroid Function Tests and antibodies |Post partum thyroiditis |Sick Euthyroid Syndrome |Thyroid Exam (OSCE) |Thyroid Gland anatomy and Physiology |Thyroid Cancer

Newborn screening for Congenital Hypothyroidism is performed via the UK "heel prick" (Guthrie) test between 5–8 days of life. The test measures TSH levels and identifies most cases of primary hypothyroidism early, preventing irreversible neurodevelopmental delay. ⚠️ It does not reliably detect central hypothyroidism.

📌 About

• Permanent hypothyroidism present at birth.
• Incidence: ~1 in 2,000–3,000 babies in the UK.
• Leading preventable cause of intellectual disability worldwide.

🧬 Aetiology

• Thyroid Dysgenesis: Abnormal thyroid development (agenesis, hypoplasia, ectopic thyroid).
• Dyshormonogenesis: Inborn errors in thyroid hormone synthesis or secretion (autosomal recessive).
• Central Hypothyroidism: Hypothalamic or pituitary dysfunction → inadequate TSH stimulation.
• Other causes: Maternal iodine deficiency, maternal thyroid disease or antithyroid drugs.

🩺 Clinical Features

• Early (first weeks): Often subtle — prolonged neonatal jaundice, hypotonia, poor feeding, lethargy, constipation, cold peripheries.
• Later if untreated: Coarse facial features, macroglossia, umbilical hernia, poor growth, developmental delay, intellectual disability.

🔎 Investigations

• Newborn bloodspot screening: Raised TSH → prompt recall and confirmatory TFTs.
• TFTs:
  • Low T4 + high TSH = primary hypothyroidism.
  • Low T4 + low/normal TSH = central hypothyroidism.
• Thyroid imaging:
  • Technetium-99m scan → presence, location, uptake of thyroid tissue.
  • Ultrasound → size, structure, absence/presence of thyroid.

💊 Management

• Levothyroxine: Start immediately once diagnosis is confirmed (dose ~10–15 mcg/kg/day).
• Monitoring: Regular TFTs in infancy, then periodic checks through childhood.
• Lifelong therapy: Most cases require lifelong replacement, though some transient cases (maternal antibodies or iodine exposure) may resolve.

💡 Key Clinical Pearl: Early treatment (within 2 weeks of birth) prevents irreversible neurocognitive impairment. Always treat first, investigate cause later. 🚼

📚 References

• NHS Newborn Blood Spot Screening Programme (UK)
• NICE: Thyroid disease: assessment and management (2019)
• European Society for Paediatric Endocrinology Guidelines