Hypothyroidism (Acquired) in children
School age children can present with primary hypothyroidism (raised TSH; low T4/T3) or central hypothyroidism (low serum TSH and low T4).
Primary hypothyroidism is commonly caused by autoimmune chronic lymphocytic thyroiditis (Hashimoto’s); but iodine deficiency is the commonest cause worldwide.
Other causes include subacute thyroiditis, drugs (like amiodarone), or thyroid gland damage by surgery, radioiodine or irradiation.
Central hypothyroidism can be caused by CNS tumours, cranial radiotherapy or pituitary anomalies.
Clinical presentation
– Symptoms can be non-specific and gradual; so can be easily missed
– Some children experience tiredness, lethargy and excessive sleepiness that can affect school performance
– Delayed puberty, reduced height velocity; but younger children may present with pseudo-precocious puberty (isolated breast development in girls or isolated testicular enlargement in boys)
– Weight-gain leading to Obesity or Slipped Upper Femoral Epiphysis
– Delayed bone age
– Dry thick myxoedematous skin, sparse hair
– Cold-intolerance, Constipation, Bradycardia
– Goiter may be a presenting feature (non-tender and firm thyroid gland, with a rubbery consistency) in primary hypothyroidism
Investigations
Confirmation of hypothyroid state with low T4 / Low T3
TSH may be elevated in primary hypothyroidism, but low in central cause
Check Thyroid antibodies against- thyroid peroxidase, thyroglobulin & TRAb (TSH receptor blocking antibodies)
Management
Adequate replacement of T4 (Thyroxine) with Oral Levothyroxine (25–200 micrograms once daily
Monitor thyroid function test every 4–6mths initially, but annually once stabilised
Monitor symptoms of under-replacement, growth, school performance and neurodevelopment. In late diagnosis, catch-up growth may be incomplete.